\n
\n \n The graph shows for model A the variation with\n \n of elastic potential energy\n \n E\n \n \n p\n \n stored in the spring.\n
\n\n \n
\n Describe the graph for model B.\n
\n\n
\n\n [2]\n
\n\n The graph shows for model A the variation with\n \n of elastic potential energy\n \n E\n \n \n p\n \n stored in the spring.\n
\n\n \n
\n Describe the graph for model B.\n
\n\n [2]\n
\n\n same curve\n \n \n OR\n \n \n shape for small amplitudes «to about 0.05 m» ✓\n
\n\n for large amplitudes «outside of 0.05 m»\n \n E\n \n \n p\n \n smaller for model B / values are lower than original / spread will be wider ✓\n \n \n OWTTE\n \n \n
\n\n
\n\n \n Accept answers drawn on graph – e.g.\n \n
\n\n \n \n \n
\n Candidates were generally successful in describing one of the two aspects of the graph of B compared to A, but few were able to describe both. It should be noted that this is a two mark question, so candidates should have considered the fact that there are two distinct statements to be made about the graphs. Examiners did accept clearly drawn graphs as well for full marks.\n
\n\n A fuel has mass density\n \n and energy density\n \n . What mass of the fuel has to be burned to release thermal energy\n \n ?\n
\n\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n \n State the number of all other points on the string that have the same amplitude and phase as X.\n \n
\n\n [1]\n
\n\n \n 3 «points» ✔\n \n
\n\n Explain, by reference to Faraday’s law of induction, how an electromotive force (emf) is induced in the coil.\n
\n\n [3]\n
\n\n \n there is a magnetic flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n in the coil / coil cuts magnetic field\n \n \n ✓\n \n
\n\n \n this flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n changes as the angle varies/coil rotates\n \n \n ✓\n \n
\n\n \n «\n \n \n Faraday’s law\n \n \n »\n \n \n connects induced emf with rate of change of flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n with time\n \n \n ✓\n \n
\n\n \n \n
\n Do not award MP2 or 3 for answers that don’t discuss flux.\n \n \n
\n This question was well answered with the majority discussing changes in flux rather than wires cutting field lines, which was good to see.\n
\n\n The tension force on the string is doubled. Describe the effect, if any, of this change on the frequency of the standing wave.\n
\n\n [2]\n
\n\n speed increases hence frequency increases ✓\n
\n\n by factor\n \n ✓\n
\n\n This question was answered well, although the numerical aspect was often missing. It is worth highlighting that if there is a term like\n \n '\n \n doubled\n \n '\n \n in the question, it makes sense to expect a numerical answer.\n
\n\n \n V\n \n is provided by two identical power supplies connected in series. The potential difference of each of the power supplies is known with an uncertainty of 0.01 kV.\n
\n\n State the uncertainty in the potential difference\n \n V\n \n .\n
\n\n [1]\n
\n\n 0.02 «kV» ✓\n
\n\n The magnetic field strength of Earth’s field at the location of the wires is 45 μT.\n
\n\n Discuss the assumption made in this question.\n
\n\n [3]\n
\n\n Use of\n \n ✓\n
\n\n \n ✓\n
\n\n Concludes that the assumption is not valid ✓\n
\n\n What are the principal roles of a moderator and of a control rod in a thermal nuclear reactor?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n Calculate the time, according to observer P, that the shuttle S takes to travel from star A to star B.\n
\n\n [2]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n \n ✓\n
\n\n = 19\n \n \n OR\n \n \n 20 «years» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for\n \n BCA\n \n \n
\n\n An object is released from rest in a vacuum at a height\n \n \n \n above the Earth’s surface.\n
\n\n As the object falls it passes a point at a height of 0.75\n \n \n \n above the surface.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n \n The variation with time\n \n t\n \n of the acceleration\n \n a\n \n of an object is shown.\n \n
\n\n \n \n \n
\n \n \n What is the change in velocity of the object from\n \n t\n \n = 0 to\n \n t\n \n = 6 s?\n
\n \n \n
\n \n \n A. 6 m s\n \n –1\n \n
\n \n \n
\n \n \n B. 8 m s\n \n –1\n \n
\n \n \n
\n \n \n C. 10 m s\n \n –1\n \n
\n \n \n
\n \n \n D. 14 m s\n \n –1\n \n \n \n
\n\n [1]\n
\n\n C\n
\n\n \n does not support the wave nature of light.\n \n
\n\n [2]\n
\n\n \n «low intensity light would» transfer energy to the electron at a low rate/slowly ✔\n
\n time would be required for the electron «to absorb the required energy» to escape/be emitted ✔\n
\n \n
\n \n \n NOTE: OWTTE\n \n \n
\n\n A student measures the time for 20 oscillations of a pendulum. The experiment is repeated four times. The measurements are:\n
\n\n 10.45 s\n
\n\n 10.30 s\n
\n\n 10.70 s\n
\n\n 10.55 s\n
\n\n What is the best estimate of the uncertainty in the average time for 20 oscillations?\n
\n\n A. 0.01 s\n
\n\n B. 0.05 s\n
\n\n C. 0.2 s\n
\n\n D. 0.5 s\n
\n\n [1]\n
\n\n C\n
\n\n This question was well answered, although option B was a significant distractor for candidates focusing on the last significant digit.\n
\n\n Slider S of the potential divider is positioned so that the ammeter reads\n \n . Explain, without further calculation, any difference in the power transferred by the potential divider arrangement over the arrangement in (b).\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n current from the cell is greater «than\n \n » ✓\n
\n\n because some of the current must flow through section SQ of the potentiometer ✓\n
\n\n overall power greater «than in part (b)» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n total/overall resistance decreases ✓\n
\n\n because SQ and X are in parallel ✓\n
\n\n overall power greater «than in part (b)» ✓\n
\n\n
\n \n Allow the reverse argument.\n \n
\n HL only. This question challenged candidate's ability to describe clearly the changes in an electrical circuit. It revealed many misconceptions about the nature of electrical current and potential difference, of those who did have a grasp of what was going on the explanations often missed the second point in each of the markscheme alternatives as detail was missed about where the current was flowing or what was in parallel with what.\n
\n\n Calculate the average translational speed of the gas particles.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Determine the moment of inertia of the system about the central axis.\n
\n\n [2]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n 33 =\n \n × 4 ✓\n
\n\n
\n\n \n = 8.25 «kg m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (a)\n \n and\n \n (b)\n \n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n \n
\n\n Sketch on the diagram the position of P at time\n \n t\n \n = 0.50 s.\n
\n\n [1]\n
\n\n P at (8, 1.2) ✓\n
\n\n A transverse water wave travels to the right. The diagram shows the shape of the surface of the water at time\n \n t\n \n = 0. P and Q show two corks floating on the surface.\n
\n\n \n
\n
\n\n «A wave where the» displacement of particles/oscillations of particles/movement of particles/vibrations of particles is perpendicular/normal to the direction of energy transfer/wave travel/wave velocity/wave movement/wave propagation ✓\n
\n\n \n Allow medium, material, water, molecules, or atoms for particles.\n \n
\n\n The charges\n \n Q\n \n are replaced by neutral masses\n \n M\n \n and the charge\n \n q\n \n by a neutral mass\n \n m\n \n . The mass\n \n m\n \n is displaced away from C by a small distance\n \n and released. Discuss whether the motion of\n \n m\n \n will be the same as that of\n \n q\n \n .\n
\n\n [2]\n
\n\n the net force will no longer be a restoring force/directed towards equilibrium\n
\n\n \n \n OR\n \n \n
\n\n the gravitational force is attractive/neutral mass would be pulled towards larger masses/\n \n \n OWTTE\n \n \n ✓\n
\n\n «and so» no, motion will not be the same/no longer be SHM /\n \n \n OWTTE\n \n \n ✓\n
\n\n The maximum intensity of sunlight incident on the photovoltaic cell at the place on the Earth’s surface is 680 W m\n \n −2\n \n .\n
\n\n A measure of the efficiency of a photovoltaic cell is the ratio\n
\n\n \n
\n\n Determine the efficiency of this photovoltaic cell when the intensity incident upon it is at a maximum.\n
\n\n [3]\n
\n\n power arriving at cell = 680 x 0.35 x 0.45 = «107 W»\n \n ✓\n \n
\n\n power in external circuit = 14.5 x 0.9 = «13.1 W»\n \n ✓\n \n
\n\n efficiency = 0.12\n \n \n OR\n \n \n 12 %\n \n ✓\n \n
\n\n \n
\n Award\n \n [3] marks\n \n for a bald correct answer\n \n
\n \n Allow\n \n ECF\n \n for\n \n MP3\n \n \n
\n\n \n Show that the intensity radiated by the oceans is about 400 W m\n \n -2\n \n .\n \n
\n\n [1]\n
\n\n \n 5.67\n \n ×\n \n 10\n \n \n −\n \n 8\n \n × 289\n \n 4\n \n \n
\n\n \n \n \n OR\n \n \n
\n \n
\n \n = 396«\n \n W m\n \n −\n \n \n \n 2\n \n » ✔\n
\n \n
\n \n «\n \n ≈\n \n 400\n \n W m\n \n −\n \n \n \n 2\n \n »\n \n
\n\n This was well answered with candidates scoring the mark for either a correct substitution or an answer given to at least one more sf than the show that value. Some candidates used 298 rather than 289.\n
\n\n The frequency of the wave is 0.50 Hz. Calculate the speed of the wave.\n
\n\n [1]\n
\n\n \n v\n \n = «0.50 × 16 =» 8.0 «m s\n \n −1\n \n » ✓\n
\n\n State the\n \n speed\n \n of the flash of light according to an observer on the ground using Einstein’s theory of relativity.\n
\n\n [1]\n
\n\n \n c\n \n ✔\n
\n\n The speed of a flash of light from different viewpoints. Most of the prepared candidates well stated the speed of the flash using Galilean relativity, Maxwell’s theory and Einstein’s theory.\n
\n\n A small magnet is released from rest to drop through a stationary horizontal conducting ring.\n
\n\n \n
\n What is the variation with time of the emf induced in the ring?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n \n Estimate, in Bq, the initial activity of the sample.\n \n
\n\n [2]\n
\n\n \n number of nuclei is\n \n \n \n ✔\n
\n \n
\n \n \n \n \n \n «\n \n \n \n »\n \n \n \n \n \n \n «Bq» ✔\n \n
\n\n Many scored the first mark for calculating the number of nuclei but neglected to convert λ to s\n \n -1\n \n .\n
\n\n A cart travels from rest along a horizontal surface with a constant acceleration. What is the variation of the kinetic energy\n \n E\n \n \n k\n \n of the cart with its distance\n \n s\n \n travelled? Air resistance is negligible.\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n Option A was the most common (incorrect) response among both HL and SL candidates, suggesting that candidates were looking for a curve representing speed rather than kinetic energy against distance. A low discrimination index suggests that both high and low achieving students were caught by this effective distractor.\n
\n\n Water at room temperature is placed in a freezer. The specific heat capacity of water is twice the specific heat capacity of ice. Assume that thermal energy is transferred from the water at a constant rate.\n
\n\n Which graph shows the variation with time of the temperature of the water?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n A standing wave is formed in a pipe closed at one end. The third harmonic has a frequency of 400 Hz when the speed of sound is 300 m s\n \n −1\n \n . What is the length of the pipe?\n
\n\n
\n A.\n \n m\n
\n B.\n \n m\n
\n\n C.\n \n m\n
\n\n D.\n \n m\n
\n\n [1]\n
\n\n B\n
\n\n The spacetime diagram shows coordinate axes of reference frames of Earth (\n \n x\n \n ,\n \n ct\n \n ) and of a spaceship (\n \n x'\n \n ,\n \n ct'\n \n ). Three events P, Q and R are plotted.\n
\n\n \n
\n Which statement is correct about the order of the events according to an observer\n \n on the spaceship\n \n ?\n
\n\n
\n A. P and Q are simultaneous, R happens later.\n
\n B. Q and R are simultaneous, P happens earlier.\n
\n\n C. Q and R are simultaneous, P happens later.\n
\n\n D. P and R are simultaneous, Q happens earlier.\n
\n\n [1]\n
\n\n D\n
\n\n Determine the recoil velocity of the cannon.\n
\n\n [3]\n
\n\n Momentum must be conserved in initial direction of shell (20° above horizontal) ✓\n
\n\n Recoil velocity is 4.2 m s\n \n −1\n \n at 20° below horizontal ✓\n
\n\n 3.95 m s\n \n −1\n \n ✓\n
\n\n An object is travelling with velocity 5 m s\n \n −1\n \n . The object then accelerates to 15 m s\n \n −1\n \n in the same direction.\n
\n\n What is the variation with time of the acceleration of the object?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n The variation with time of the displacement of an object is shown.\n
\n\n \n
\n What are the average speed and average velocity of the object over the 10 s time interval?\n
\n\n
\n| \n | \n\n \n Average speed / m s\n \n −1\n \n \n | \n\n \n Average velocity / m s\n \n −1\n \n \n \n | \n
| \n A.\n | \n\n 0.8\n | \n\n 0.8\n | \n
| \n B.\n | \n\n 0.8\n | \n\n 1.2\n | \n
| \n C.\n | \n\n 1.2\n | \n\n 0.8\n | \n
| \n D.\n | \n\n 1.2\n | \n\n 1.2\n | \n
\n
\n\n [1]\n
\n\n C\n
\n\n State what is meant by an ideal voltmeter.\n
\n\n [1]\n
\n\n infinite resistance\n
\n\n \n \n OR\n \n \n
\n\n no current is flowing through it ✓\n
\n\n A majority of candidates scored a mark by simply stating infinite resistance. Several answers went the other way round, stating a resistance of zero.\n
\n\n Discuss the variation in the power output of the motor with distance from the lower station.\n
\n\n [2]\n
\n\n The pd across the motor increases as the tram travels up the track ✓\n
\n\n (As the current is constant), the power output also rises ✓\n
\n\n Determine the fundamental SI unit for\n \n a\n \n .\n
\n\n [2]\n
\n\n kg m s\n \n −2\n \n \n \n OR\n \n \n m\n \n 2\n \n s\n \n −2\n \n seen ✓\n
\n\n kg m\n \n −1\n \n ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n .\n \n
\n\n Students seem to be well prepared for this sort of question, as it was high-scoring.\n
\n\n State what is meant by a transverse wave.\n
\n\n [1]\n
\n\n «A wave where the» displacement of particles/oscillations of particles/movement of particles/vibrations of particles is perpendicular/normal to the direction of energy transfer/wave travel/wave velocity/wave movement/wave propagation ✓\n
\n\n \n Allow medium, material, water, molecules, or atoms for particles.\n \n
\n\n The energy levels\n \n E\n \n of an atom are shown.\n
\n\n \n
\n Which emission spectrum represents the transitions?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n A planet orbits the Sun in an elliptical orbit moving in the direction shown.\n
\n\n \n
\n At the position shown, which quantity is decreasing for the planet?\n
\n\n
\n A. Acceleration\n
\n B. Angular momentum\n
\n\n C. Kinetic energy\n
\n\n D. Gravitational potential energy\n
\n\n [1]\n
\n\n D\n
\n\n Planet\n \n and planet\n \n both emit radiation as black bodies. Planet\n \n has twice the surface temperature and one third of the radius of planet\n \n .\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n A cell of negligible internal resistance and electromotive force (emf) 6.0 V is connected to three resistors R, P and Q.\n
\n\n \n
\n R is an ohmic resistor. The\n \n I-V\n \n characteristics of P and Q are shown in the graph.\n
\n\n \n
\n The current in P is 0.40 A.\n
\n\n
\n\n Voltage across P is 1.4 «V» ✓\n
\n\n Voltage across Q is 4.6 «V» ✓\n
\n\n And 6 – 1.4 = 4.6 «V» ✓\n
\n\n
\n\n \n Need to see a calculation involving the two voltages and the total voltage in the circuit for\n \n MP3\n \n (e.g. 1.4 + 4.6 = 6).\n \n
\n\n \n Which graph shows the relationship between gravitational force\n \n F\n \n between two point masses and their separation\n \n r\n \n ?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n Show that the speed of the loop is 20 cm s\n \n −1\n \n .\n
\n\n [1]\n
\n\n \n ✓\n
\n\n The intensity pattern of monochromatic light of wavelength λ, is projected onto a screen.\n
\n\n \n
\n What combination produces this pattern?\n
\n\n
\n| \n | \n\n \n Number of slits\n \n | \n\n \n Width of slits\n \n \n | \n
| \n A.\n | \n\n 1\n | \n\n smaller than λ\n | \n
| \n B.\n | \n\n 1\n | \n\n greater than λ\n | \n
| \n C.\n | \n\n 2\n | \n\n smaller than λ\n | \n
| \n D.\n | \n\n 2\n | \n\n greater than λ\n | \n
\n
\n\n [1]\n
\n\n D\n
\n\n Estimate the displacement needed to double the energy of the string.\n
\n\n [2]\n
\n\n use of\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n A particle undergoes simple harmonic motion. Which quantities of the motion can be simultaneously zero?\n
\n\n A. Displacement and velocity\n
\n\n B. Displacement and acceleration\n
\n\n C. Velocity and acceleration\n
\n\n D. Displacement, velocity and acceleration\n
\n\n [1]\n
\n\n B\n
\n\n Which is a correct unit for gravitational potential?\n
\n\n A. m\n \n 2\n \n s\n \n −2\n \n
\n\n B. J kg\n
\n\n C. m s\n \n −2\n \n
\n\n D. N m\n \n −1\n \n kg\n \n −1\n \n
\n\n [1]\n
\n\n A\n
\n\n Explain why the change of entropy for the gas during the process BC is equal to zero.\n
\n\n [1]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «the process is adiabatic so» ΔQ = 0 ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n The compression is reversible «so ΔS = 0» ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Show that\n \n .\n
\n\n [2]\n
\n\n Equates centripetal force (with Newton’s law of gravitation\n \n )\n
\n\n \n \n OR\n \n \n
\n\n \n ✓\n
\n\n
\n Uses both equation correctly with clear re-arrangement ✓\n
\n State\n \n two\n \n assumptions of the kinetic model of an ideal gas that refer to intermolecular collisions.\n
\n\n [2]\n
\n\n The collisions are elastic ✓\n
\n\n The time for a collision is much shorter than the time between collisions ✓\n
\n\n The intermolecular forces are only present during collisions ✓\n
\n\n Determine the terminal velocity of the sphere.\n
\n\n [3]\n
\n\n radius of sphere\n \n ✓\n
\n\n
\n\n weight of sphere\n \n
\n\n \n \n OR\n \n \n
\n\n \n ✓\n
\n\n
\n\n \n ✓\n
\n\n
\n\n \n \n Accept use of\n \n leading to\n \n \n \n
\n\n \n \n Allow implicit calculation of radius for MP1\n \n \n
\n\n \n \n Do not allow ECF for MP3 if buoyant force omitted.\n \n \n
\n\n Only those candidates who forgot to include the buoyant force missed marks here.\n
\n\n To determine\n \n T\n \n more precisely, the student measures the total time for 20 oscillations and divides by 20.\n
\n\n Explain why this is preferable to measuring the time for just one oscillation.\n
\n\n [2]\n
\n\n it reduces «the random» error/uncertainty ✓\n
\n\n by a factor of 20 «compared to that in a single period measurement» ✓\n
\n\n
\n\n \n For\n \n MP1\n \n , allow increasing accuracy/precision.\n \n
\n\n \n \n Award [0]\n \n for answers related to number of trials, 20 measurements of one period.\n \n
\n\n A positive point charge of magnitude 1.0 μC and a point charge\n \n q\n \n are separated by a distance\n \n d\n \n .\n
\n\n \n
\n An electron is placed at a distance\n \n d\n \n from the +1.0 μC charge. The electric force on the electron is zero.\n
\n\n What is\n \n q\n \n ?\n
\n\n
\n A. −4.0 μC\n
\n B. −2.0 μC\n
\n\n C. 2.0 μC\n
\n\n D. 4.0 μC\n
\n\n [1]\n
\n\n A\n
\n\n The gravitational potential due to the mass of M at the surface of P can be assumed to be negligible.\n
\n\n Estimate, using the graph, the gravitational potential at the surface of M due to the mass of M.\n
\n\n [2]\n
\n\n «\n \n =\n \n = 0.75 × 0.27» = 0.20 ✓\n
\n\n \n V\n \n \n M\n \n = «−6.4 × 10\n \n 7\n \n × 0.2 =» «−»1.3 × 10\n \n 7\n \n «J kg\n \n −1\n \n »✓\n
\n\n A simple pendulum undergoes simple harmonic motion. The gravitational potential energy of the pendulum is zero at the equilibrium position. How many times during\n \n one\n \n oscillation is the kinetic energy of the pendulum equal to its gravitational potential energy?\n
\n\n
\n A. 1\n
\n B. 2\n
\n\n C. 3\n
\n\n D. 4\n
\n\n [1]\n
\n\n D\n
\n\n Calculate the scattering angle of the photon.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n Outline\n \n two\n \n reasons why both models predict that the motion is simple harmonic when\n \n is small.\n
\n\n [2]\n
\n\n \n \n For both models:\n \n \n
\n displacement is ∝ to acceleration/force «because graph is straight and through origin» ✓\n
\n displacement and acceleration / force in opposite directions «because gradient is negative»\n
\n \n \n OR\n \n \n
\n acceleration/«restoring» force is always directed to equilibrium ✓\n
\n This item was essentially encouraging candidates to connect concepts about simple harmonic motion to a physical situation described by a graph. The marks were awarded for discussing the physical motion (such as \"the acceleration is in the opposite direction of the displacement\") and not just for describing the graph itself (such as \"the slope of the graph is negative\"). Most candidates were successful in recognizing that the acceleration was proportional to displacement for the first marking point, but many simply described the graph for the second marking point.\n
\n\n The coefficient of dynamic friction between the block and the rough surface is 0.400.\n
\n\n Estimate the distance travelled by the block on the rough surface until it stops.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n Frictional force is\n \n f\n \n «= 0.400 × 2.40 × 9.81» = 9.42 «N» ✓\n
\n 9.42 ×\n \n d\n \n =\n \n × 2.40 × 2.16\n \n 2\n \n \n \n OR\n \n \n \n d\n \n =\n \n ✓\n
\n \n d\n \n = 0.594 «m» ✓\n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n \n a\n \n = «\n \n =\n \n µg\n \n = 0.4 × 9.81 =» 3.924 «m s\n \n −2\n \n » ✓\n
\n Proper use of kinematics equation(s) to determine ✓\n
\n\n \n d\n \n = 0.594 «m» ✓\n
\n\n A spaceship is travelling at 0.60\n \n c\n \n from Earth when it launches a probe at 0.10\n \n c\n \n relative to the spaceship and away from Earth.\n
\n\n What is the speed of the probe relative to Earth?\n
\n\n
\n A. 0.50\n \n c\n \n
\n B. 0.66\n \n c\n \n
\n\n C. 0.75\n \n c\n \n
\n\n D. 0.90\n \n c\n \n
\n\n [1]\n
\n\n B\n
\n\n Outline the origin of the force that acts on Phobos.\n
\n\n [1]\n
\n\n gravitational attraction/force/field «of the planet/Mars» ✔\n
\n\n \n Do not accept “gravity”\n \n .\n
\n\n This was generally well answered, although some candidates simply used the vague term “gravity” rather than specifying that it is a gravitational force or a gravitational field. Candidates need to be reminded about using proper physics terms and not more general, “every day” terms on the exam.\n
\n\n Outline how a standing wave is produced on the string.\n
\n\n [2]\n
\n\n «travelling» wave moves along the length of the string and reflects «at fixed end»\n \n ✓\n \n
\n\n superposition/interference of incident and reflected waves\n \n ✓\n \n
\n\n the superposition of the reflections is reinforced only for certain wavelengths\n \n ✓\n \n
\n\n Draw on the graph the position of the missing point for the Δ\n \n p\n \n value of 40 kPa.\n
\n\n [1]\n
\n\n point plotted at (40 kPa, 49 × 10\n \n 5\n \n N\n \n 3\n \n ) ✓\n
\n\n \n
\n Allow for the point to be plotted from 46 to 56 × 10\n \n 5\n \n N\n \n 3\n \n at 40 kPa, as candidates may calculate or may plot from a graphical analysis.\n \n
\n Diagram 1 shows the variation with position of the displacement of a standing wave formed on a string.\n
\n\n Diagram 2 shows the variation with position of the displacement of a travelling wave moving to the right along a string.\n
\n\n \n
\n Points P, Q, R and S are points on the string.\n
\n\n What is the phase difference between P and Q and the phase difference between R and S?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n A stuntman rides a motorcycle on the inside surface of a cylinder.\n
\n\n \n
\n Which is the correct free-body diagram showing all the forces acting on the cyclist at that position?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n State the nature and direction of the force that accelerates the 15 kg object.\n
\n\n [1]\n
\n\n static friction force «between blocks»\n
\n\n \n AND\n \n
\n\n directed to the right ✓\n
\n\n Calculate the angular impulse applied to the flywheel.\n
\n\n [2]\n
\n\n Attempt to find area of triangle ✓\n
\n\n \n «kg m\n \n 2\n \n s\n \n −1\n \n » ✓\n
\n\n \n Calculate, in hours, the time at which the activity of the sample has decreased to one-third of the initial activity.\n \n
\n\n [2]\n
\n\n \n \n \n \n \n \n ✔\n
\n \n
\n \n \n t\n \n = 20«hr» ✔\n \n
\n\n This was very well answered with the majority of candidates scoring full marks. This is a good indication that candidates weren’t short of time in this paper.\n
\n\n A resistor of resistance\n \n R\n \n is connected to a fully charged cell of negligible internal resistance. A constant power\n \n P\n \n is dissipated in the resistor and the cell discharges in time\n \n t\n \n . An identical cell is connected in series with two identical resistors each of resistance\n \n R\n \n .\n
\n\n What is the power dissipated in each resistor and the time taken to discharge the cell?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n This question was not well answered, with fewer than 25 % of candidates correctly selecting response B. Furthermore, the discrimination index for this question was remarkably low, suggesting this question would provide rich classroom discussion.\n
\n\n \n Calculate, in Hz, the frequency for this wave.\n \n
\n\n [2]\n
\n\n \n \n λ\n \n = 0.30 «m» ✔\n
\n \n = «\n \n » 830 «Hz» ✔\n \n
\n \n NOTE:\n \n \n \n Allow ECF from (a)(i)\n
\n Allow ECF from wrong wavelength for MP2\n \n \n
\n The concept of potential is also used in the context of gravitational fields. Suggest why scientists developed a common terminology to describe different types of fields.\n
\n\n [1]\n
\n\n \n to highlight similarities between\n \n \n «\n \n \n different\n \n \n »\n \n \n fields\n \n \n ✓\n \n
\n\n This was generally well answered with only a small number of answers suggesting greater international cooperation.\n
\n\n The player’s foot is in contact with the ball for 55 ms. Calculate the average force that acts on the ball due to the football player.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Allow\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n if 19 sin22\n \n OR\n \n 19 cos22 used.\n \n
\n\n A longitudinal wave is travelling through a medium. The variation with distance\n \n d\n \n of the displacement\n \n of the particles in the medium at time\n \n t\n \n is shown.\n
\n\n Which point is at the centre of a compression?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n \n Determine, with reference to the work done by the average force, the horizontal distance travelled by the ball while it was in contact with the racket.\n \n
\n\n [3]\n
\n\n \n E\n \n \n k\n \n \n =\n \n ×\n \n 5.8 × 10\n \n –2\n \n × 14.5\n \n 2\n \n ✔\n
\n\n \n E\n \n \n k\n \n =\n \n W\n \n ✔\n \n \n
\n\n \n \n \n s =\n \n \n \n \n «\n \n » 0.12 « m » ✔\n \n \n \n
\n\n
\n\n \n Allow ECF from (a) and (b)\n \n
\n\n \n Allow ECF from MP1\n \n
\n\n \n Award\n \n [2]\n \n max for a calculation without reference to work done, eg: average velocity × time\n \n
\n\n Four identical resistors, each of resistance\n \n , are connected as shown.\n
\n\n \n
\n What is the effective resistance between P and Q?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Show that the speed of the load when it hits the floor is about 2.1 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n proper use of kinematic equation ✓\n
\n\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Must see either the substituted values\n \n OR\n \n a value for v to at least three s.f. for\n \n MP2\n \n .\n \n
\n\n This was a \"show that\" questions, so examiners were looking for a clear equation leading to a clear substitution of values leading to an answer that had more significant digits than the given answer. Most candidates successfully selected the correct equation and showed a proper substitution. Some candidates started with an energy approach that needed modification as it clearly led to an incorrect solution. These responses did not receive full marks.\n
\n\n State the principal energy change in nuclear fission.\n
\n\n [1]\n
\n\n Mass-energy «of uranium» into kinetic energy of fission products ✓\n
\n\n Calculate the pressure of the gas at B.\n
\n\n [2]\n
\n\n use of\n \n pV\n \n = constant ✓\n
\n\n \n P\n \n \n B\n \n = 43 «Kpa» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n The photoelectrons are emitted from a sodium surface. Sodium has a work function of 2.3 eV.\n
\n\n Calculate the wavelength of the radiation incident on the sodium. State an appropriate unit for your answer.\n
\n\n [3]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Must see an appropriate unit to award\n \n MP3.\n \n \n
\n B is placed at the first minimum. The frequency is then changed until the received intensity is again at a maximum.\n
\n\n Show that the lowest frequency at which the intensity maximum can occur is about 3 kHz.\n
\n\n Speed of sound = 340 m s\n \n −1\n \n
\n\n [2]\n
\n\n «\n \n » = 13 cm ✓\n
\n\n \n «\n \n » 2.6 «kHz» ✓\n
\n\n
\n\n \n Allow ½ of wavelength from (b) or data from graph for\n \n MP1\n \n .\n \n
\n\n \n Allow ECF from\n \n MP1\n \n .\n \n
\n\n This was a \"show that\" question that had enough information for backwards working. Examiners were looking for evidence of using the wavelength from (b) or information from the graph to determine wavelength followed by a correct substitution and an answer to more significant digits than the given result.\n
\n\n A ball of mass 0.3 kg is attached to a light, inextensible string. It is rotated in a vertical circle. The length of the string is 0.6 m and the speed of rotation of the ball is 4 m s\n \n −1\n \n .\n
\n\n \n
\n What is the tension when the string is horizontal?\n
\n\n A. 5 N\n
\n\n B. 8 N\n
\n\n C. 11 N\n
\n\n D. 13 N\n
\n\n [1]\n
\n\n B\n
\n\n This question was well answered by both HL and SL candidates with a high difficulty index for each paper.\n
\n\n A net force of 8.0 N accelerates a 4.0 kg body from rest to a speed of 5.0 m s\n \n −1\n \n .\n
\n\n What is the work done by the force?\n
\n\n
\n A. 50 J\n
\n B. 40 J\n
\n\n C. 32 J\n
\n\n D. 20 J\n
\n\n [1]\n
\n\n A\n
\n\n Three statements about a nuclear fission reactor are:\n
\n\n I. The heat exchanger transfers energy from the fuel rods to the moderator.\n
\n II. The control rods must be good absorbers of neutrons.\n
\n III. The moderator must slow neutrons down.\n
\n Which statements about the reactor are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n C\n
\n\n An object of mass 1.0 kg hangs at rest from a spring. The spring has a negligible mass and the spring constant\n \n k\n \n is 20 N m\n \n −1\n \n
\n\n \n
\n What is the elastic potential energy stored in the spring?\n
\n\n
\n A. 1.0 J\n
\n B. 2.5 J\n
\n\n C. 5.0 J\n
\n\n D. 10 J\n
\n\n [1]\n
\n\n B\n
\n\n A quantity of 2.00 mol of an ideal gas is maintained at a temperature of 127 ºC in a container of volume 0.083 m\n \n 3\n \n . What is the pressure of the gas?\n
\n\n A. 8 kPa\n
\n\n B. 25 kPa\n
\n\n C. 40 kPa\n
\n\n D. 80 kPa\n
\n\n [1]\n
\n\n D\n
\n\n In another situation the rod rests on a horizontal frictionless surface with no pivot. Predict, without calculation, the motion of the rod–particle system after the collision.\n
\n\n [2]\n
\n\n the rod will rotate «about centre of mass» ✓\n
\n\n «centre of mass» will move along straight line\n
\n «parallel to the particle’s initial velocity» ✓\n
\n
\n\n \n For\n \n MP2\n \n , mention of translational motion is not enough.\n \n
\n\n The age of the Earth is about 4.5 × 10\n \n 9\n \n years.\n
\n\n What area of physics provides experimental evidence for this conclusion?\n
\n\n A. Newtonian mechanics\n
\n\n B. Optics\n
\n\n C. Radioactivity\n
\n\n D. Electromagnetism\n
\n\n [1]\n
\n\n C\n
\n\n A comet orbits the Sun in an elliptical orbit. A and B are two positions of the comet.\n
\n\n \n
\n Explain, with reference to Kepler’s second law of planetary motion, the change in the kinetic energy of the comet as it moves from A to B.\n
\n\n [3]\n
\n\n The areas swept out in unit time by the Sun-comet line are the same at A and B ✓\n
\n\n At B, the distance is greater hence the orbital speed/distance moved in unit time is lower «so that the area remains the same» ✓\n
\n\n A decrease in speed means that the kinetic energy also decreases ✓\n
\n\n \n Explain how the student could use this apparatus to obtain a more reliable value for λ.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1:\n \n \n
\n \n
\n \n measure the combined width for several fringes\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n repeat measurements ✓\n
\n \n
\n \n take the average\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n so the «percentage» uncertainties are reduced ✓\n
\n \n
\n \n \n \n ALTERNATIVE 2:\n \n \n
\n \n
\n \n increase\n \n D\n \n «hence\n \n s\n \n »\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n Decrease\n \n d\n \n ✓\n
\n \n
\n \n so the «percentage» uncertainties are reduced ✓\n \n
\n\n \n \n \n Do not accept answers which suggest using different apparatus.\n \n \n \n
\n\n The most common correct answer was the readings should be repeated and an average taken. Another common answer was that D could be increased to reduce uncertainties in s. The best candidates knew that it was good practice to measure many fringe spacings and find the mean value. Quite a few candidates incorrectly stated that different apparatus should be used to give more precise results.\n
\n\n The frequency of the wave is 0.50 Hz. Calculate the speed of the wave.\n
\n\n [1]\n
\n\n \n v\n \n = «0.50 × 16 =» 8.0 «m s\n \n −1\n \n » ✓\n
\n\n A simple pendulum has a time period\n \n \n \n on the Earth. The pendulum is taken to the Moon where the gravitational field strength is\n \n that of the Earth.\n
\n\n What is the time period of the pendulum on the Moon?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Explain why intensity maxima are observed at X and Y.\n
\n\n [2]\n
\n\n two waves superpose/mention of superposition/mention of «constructive» interference ✔\n
\n\n they arrive in phase/there is a path length difference of an integer number of wavelengths ✔\n
\n\n \n Ignore references to nodes/antinodes\n \n .\n
\n\n Many candidates were able to discuss the interference that is taking place in this question, but few were able to fully describe the path length difference. That said, the quality of responses on this type of question seems to have improved over the last few examination sessions with very few candidates simply discussing the crests and troughs of waves.\n
\n\n Outline\n \n one\n \n reason why the maxima observed at W, X and Y will have different intensities from each other.\n
\n\n [1]\n
\n\n intensity is modulated by a single slit diffraction envelope\n \n \n OR\n \n \n
\n\n intensity varies with distance\n \n \n OR\n \n \n points are different distances from the slits ✔\n
\n
\n
\n This is one of many questions on this paper where candidates wrote vague answers that did not clearly connect to physics concepts or include key information. There were many overly simplistic answers like “they are farther away” without specifying what they are farther away from. Candidates should be reminded that their responses should go beyond the obvious and include some evidence of deeper understanding.\n
\n\n Determine\n \n . State your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n \n «\n \n \n lift force/change of momentum in one second\n \n \n »\n \n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n \n \n AND\n \n \n \n \n answer expressed to\n \n sf only\n \n \n ✓\n \n
\n\n \n Allow\n \n from\n \n \n .\n
\n\n The diagram shows an interference pattern observed on a screen in a double-slit experiment with monochromatic light of wavelength 600 nm. The screen is 1.0 m from the slits.\n
\n\n \n
\n What is the separation of the slits?\n
\n\n
\n A. 6.0 × 10\n \n −7\n \n m\n
\n B. 6.0 × 10\n \n −6\n \n m\n
\n\n C. 6.0 × 10\n \n −5\n \n m\n
\n\n D. 6.0 × 10\n \n −4\n \n m\n
\n\n [1]\n
\n\n D\n
\n\n Another black body is on the Moon’s surface at point B.\n
\n\n Outline, without calculation, why the aximum temperature of the black body at point B is less than at point A.\n
\n\n [2]\n
\n\n energy/Power/Intensity lower at B ✔\n
\n\n connection made between energy/power/intensity and temperature of blackbody ✔\n
\n\n This is question is another example of candidates not thinking beyond the obvious in the question. Many simply said that point B is farther away, or that it is at an angle. Some used vague terms like “the sunlight is more spread out” rather than using proper physics terms. Few candidates connected the lower intensity at B with the lower temperature of the blackbody.\n
\n\n Explain, by reference to charge carriers in the wire, how the magnetic force on the wire arises.\n
\n\n [2]\n
\n\n charge/carriers are moving in a magnetic field ✓\n
\n\n
\n\n there is a magnetic force on them / quote\n \n F = qvB\n \n
\n\n \n \n OR\n \n \n
\n\n this creates a magnetic field that interacts with the external magnetic field ✓\n
\n\n
\n\n \n Accept electrons.\n \n
\n\n \n For\n \n MP2\n \n , the force must be identified as acting on charge / carriers.\n \n
\n\n Many scored MP1 here but did not get MP2 as they jumped straight to the wire rather than continuing with the explanation of what was going on with the charge carriers.\n
\n\n A resistor connects two parallel conducting rails a distance\n \n d\n \n apart. A conducting bar rolls along the rails at a constant velocity\n \n v\n \n through a uniform magnetic field of 2.0 T perpendicular to the rails as shown.\n
\n\n The voltage\n \n V\n \n across the resistor is measured.\n
\n\n \n
\n The graph shows the variation of\n \n V\n \n with\n \n d\n \n .\n
\n\n \n
\n What is\n \n v\n \n ?\n
\n\n
\n A. 0.33 m s\n \n −1\n \n
\n B. 3.0 m s\n \n −1\n \n
\n\n C. 6.0 m s\n \n −1\n \n
\n\n D. 12.0 m s\n \n −1\n \n
\n\n [1]\n
\n\n B\n
\n\n Determine the magnetic force acting on the 15 Ω wire due to the current in the 30 Ω wire.\n
\n\n [4]\n
\n\n Use of combination of resistors OR\n \n ✓\n
\n\n To show that current in 30 Ω wire is 5.0 A ✓\n
\n\n \n ✓\n
\n\n \n N ✓\n
\n\n \n Identify, on the HR diagram, the position of the Sun. Label the position S.\n \n
\n\n [1]\n
\n\n \n the letter S should be in the region of the shaded area\n \n \n \n ✔\n \n \n
\n\n \n \n \n
\n Locating the Sun’s position on the HR diagram was correctly done by most candidates, although a few were unsure of the surface temperature of the Sun.\n
\n\n Calculate the internal resistance of the photovoltaic cell for the maximum intensity condition using the model for the cell.\n
\n\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n pd dropped across cell\n \n ✓\n
\n internal resistance\n \n ✓\n
\n\n \n \n ✓\n \n
\n\n \n \n
\n ALTERNATIVE 2\n \n \n
\n \n \n so\n \n \n ✓\n \n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Alternative solutions are possible\n \n
\n \n Award\n \n [3]\n \n marks for a bald correct answer\n \n
\n\n Describe the motion of Q after release.\n
\n\n [2]\n
\n\n Q moves to the right/away from P «along a straight line»\n
\n\n \n \n OR\n \n \n
\n\n Q is repelled from P ✓\n
\n\n
\n with increasing speed/Q accelerates ✓\n
\n acceleration decreases ✓\n
\n\n The diagram shows, for a region on the Earth’s surface, the incident, radiated and reflected intensities of the solar radiation.\n
\n\n \n
\n What is the albedo of the region?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n This question was well answered by both HL and SL candidates.\n
\n
\n
\n The diameter of a nucleus of a particular nuclide X is\n \n . What is the nucleon number of X?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Two blocks X and Y at different temperatures are placed in thermal contact with each other until they reach thermal equilibrium. Block X and block Y are of the same material. The mass of block Y is half that of block X. The change in temperature of block X has a magnitude Δ\n \n T\n \n and the change in internal energy of block X has a magnitude Δ\n \n U\n \n . What is the change in magnitude of temperature of block Y and the change in magnitude of internal energy of block Y?\n
\n\n
\n| \n | \n\n \n Magnitude of change\n \n \n \n in temperature of Y\n \n | \n \n \n Magnitude of change in\n \n \n \n internal energy of Y\n \n | \n
| \n A.\n | \n\n Δ\n \n T\n \n | \n\n 2Δ\n \n U\n \n | \n
| \n B.\n | \n\n 2Δ\n \n T\n \n | \n\n 2Δ\n \n U\n \n | \n
| \n C.\n | \n\n Δ\n \n T\n \n | \n\n Δ\n \n U\n \n | \n
| \n D.\n | \n\n 2Δ\n \n T\n \n | \n\n Δ\n \n U\n \n | \n
\n
\n\n [1]\n
\n\n D\n
\n\n Three stars P, Q and R are plotted in the Hertzsprung-Russel diagram with empty circles.\n
\n\n \n
\n Which of the following lists the stars in the order of increasing radius?\n
\n\n
\n A. Q, R, P\n
\n B. P, R, Q\n
\n\n C. R, Q, P\n
\n\n D. R, P, Q\n
\n\n [1]\n
\n\n D\n
\n\n Outline why component X is considered non-ohmic.\n
\n\n [1]\n
\n\n \n current is not «directly» proportional to the potential difference\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X is not constant\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X changes «with current/voltage»\n \n \n ✓\n \n
\n An object of mass\n \n is launched from the surface of the Earth. The Earth has a mass\n \n and radius\n \n . The acceleration due to gravity at the surface of the Earth is\n \n . What is the escape speed of the object from the surface of the Earth?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Options B and C were selected by a roughly equal number of candidates. Again, this is a situation where unit analysis is beneficial; options C and D would not produce units associated with speed (mass is already incorporated in the constant 'g').\n
\n\n Four identical lamps are connected in a circuit. The current through lamp L is\n \n I\n \n .\n
\n\n \n
\n The lamps are rearranged using the same cell.\n
\n\n \n
\n What is the current through L?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n I\n \n
\n\n D. 2\n \n I\n \n
\n\n [1]\n
\n\n C\n
\n\n P and R are parallel wires carrying the same current into the plane of the paper. P and R are equidistant from a point Q. The line PQ is perpendicular to the line RQ.\n
\n\n \n
\n The magnetic field due to P at Q is\n \n \n \n . What is the magnitude of the resultant magnetic field at Q due to both wires?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n State the speed of shuttle S relative to observer P using Galilean relativity.\n
\n\n [1]\n
\n\n «−» 0.48\n \n c\n \n ✓\n
\n\n
\n\n \n Ignore sign\n \n
\n\n An object of mass 2.0 kg rests on a rough surface. A person pushes the object in a straight line with a force of 10 N through a distance\n \n d\n \n .\n
\n\n \n
\n The resultant force acting on the object throughout\n \n d\n \n is 6.0 N.\n
\n\n What is the value of the sliding coefficient of friction\n \n \n \n between the surface and the object and what is the acceleration\n \n a\n \n of the object?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n There is no evidence that candidates were disadvantaged by the use of sliding friction rather than dynamic friction with the correct option being the most popular.\n
\n\n \n The positions of stable nuclei are plotted by neutron number\n \n n\n \n and proton number\n \n p\n \n . The graph indicates a dotted line for which\n \n n = p\n \n . Which graph shows the line of stable nuclides and the shaded region where unstable nuclei emit beta minus (β\n \n -\n \n ) particles?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n This question proved challenging, a low discrimination index and a relatively even spread of answers suggests that maybe guesswork was responsible for the candidates choice.\n
\n\n A sky diver is falling at terminal speed when she opens her parachute. What are the direction of her velocity vector and the direction of her acceleration vector before she reaches the new terminal speed?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n A girl throws an object horizontally at time\n \n t\n \n = 0. Air resistance can be ignored. At\n \n t\n \n = 0.50 s the object travels horizontally a distance\n \n \n \n in metres while it falls vertically through a distance\n \n \n \n in metres.\n
\n\n What is the initial velocity of the object and the vertical distance fallen at\n \n t\n \n = 1.0 s?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n The correct response (D) was the most common selection by a minority of candidates, with incorrect responses being roughly equally distributed among the remaining options. This question has one of the highest discrimination indexes.\n
\n\n A sample of a pure radioactive nuclide initially contains\n \n atoms. The initial activity of the sample is\n \n .\n
\n\n A second sample of the same nuclide initially contains\n \n atoms.\n
\n\n What is the activity of the second sample after three half lives?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Calculate, in s\n \n −1\n \n , the initial activity of the sample.\n
\n\n [1]\n
\n\n \n «s\n \n −1\n \n » ✓\n
\n\n Compare the internal energy of the chocolate at\n \n t\n \n = 2 minutes with that at\n \n t\n \n = 6 minutes.\n
\n\n [2]\n
\n\n Internal energy is greater at\n \n t\n \n = 6 min\n \n \n OR\n \n \n internal energy is lower at\n \n t\n \n = 2 min\n \n \n OR\n \n \n internal energy increases «as energy is added to the system» ✓\n
\n\n Because kinetic energy «of the molecules» is the same\n \n \n AND\n \n \n potential energy «of the molecules» has increased /\n \n \n OWTTE\n \n \n ✓\n
\n\n The diagram shows the emission spectrum of an atom.\n
\n\n \n
\n Which of the following atomic energy level models can produce this spectrum?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Show that the collision is elastic.\n
\n\n [4]\n
\n\n Use of conservation of momentum. ✓\n
\n Rebound speed = 2.16 «m s\n \n −1\n \n » ✓\n
\n Calculation of initial KE = «\n \n × 0.800 × 4.317\n \n 2\n \n » = 7.46 « J » ✓\n
\n Calculation of final KE = «\n \n × 0.800 × 2.16\n \n 2\n \n +\n \n × 2.40 × 2.16\n \n 2\n \n » = 7.46 «J» ✓\n
\n «hence elastic»\n
\n \n A transverse travelling wave is moving through a medium. The graph shows, for one instant, the variation with distance of the displacement of particles in the medium.\n \n
\n\n \n \n \n
\n \n \n The frequency of the wave is 25 Hz and the speed of the wave is 100 m s\n \n –1\n \n . What is correct for this wave?\n
\n \n \n
\n
\n\n \n \n A. The particles at X and Y are in phase.\n
\n \n \n
\n \n \n B. The velocity of the particle at X is a maximum.\n
\n \n \n
\n \n \n C. The horizontal distance between X and Z is 3.0 m.\n
\n \n \n
\n \n \n D. The velocity of the particle at Y is 100 m s\n \n –1\n \n .\n \n \n
\n\n [1]\n
\n\n C\n
\n\n Estimate, in °C, the temperature of the roof tiles.\n
\n\n [3]\n
\n\n absorbed intensity = (1 − 0.2) × 680 «= 544» «W m\n \n −2\n \n »\n
\n\n \n \n OR\n \n \n
\n\n emitted intensity = 0.97 × 5.67 × 10\n \n −8\n \n × T\n \n 4\n \n ✓\n
\n\n
\n\n \n T\n \n \n «K» ✓\n
\n\n 42 «°C» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Allow\n \n MP1\n \n if absorbed or emitted intensity is multiplied by area.\n \n
\n\n This was a bit more hit and miss than the previous question part. One common mistake was not understanding what albedo meant. Some took it as the amount of energy absorbed rather than reflected. Emissivity was often missed. Several candidates, successfully answering the question or not, were able to score MP3 converting the final temperature into Celsius degrees.\n
\n\n Calculate the component of momentum of the first curling stone perpendicular to the initial direction.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n \n An object has a weight of 6.10 × 10\n \n 2\n \n N. What is the change in gravitational potential energy of the object when it moves through 8.0 m vertically?\n
\n \n
\n \n A. 5 kJ\n
\n \n
\n \n B. 4.9 kJ\n
\n \n
\n \n C. 4.88 kJ\n
\n \n
\n \n D. 4.880 kJ\n \n
\n\n [1]\n
\n\n B\n
\n\n At SL, more candidates chose C with B the second most popular response. This question was about significant figures and candidates should be reminded that on the multiple choice paper they are not expected to perform detailed calculations. In this case 6.10 (to 3 sig figs) times 8.0 (to 2 sig figs) produces an answer to 2 sig figs giving B as the correct response. All answers are equivalent from a numerical point of view with the difference being the number of sig figs used.\n
\n\n A nucleus of americium-241 has 146 neutrons. This nuclide decays to neptunium through alpha emission.\n
\n\n Complete the nuclear equation for this decay.\n
\n\n \n
\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n Two coils of wire are wound around an iron cylinder. One coil is connected in a circuit with a cell and a switch that is initially closed. The other coil is connected to an ammeter. The switch is opened at time\n \n t\n \n \n 0\n \n .\n
\n\n \n
\n What is the ammeter reading before\n \n t\n \n \n 0\n \n and what is the ammeter reading after\n \n t\n \n \n 0\n \n ?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n State\n \n one\n \n way in which a real gas differs from an ideal gas.\n
\n\n [1]\n
\n\n can be liquefied ✓\n
\n\n has intermolecular forces / potential energy ✓\n
\n\n has atoms/molecules that are not point objects / take up volume ✓\n
\n\n does not follow the ideal gas law «for all\n \n T\n \n and\n \n p\n \n » ✓\n
\n\n collisions between particles are non-elastic ✓\n
\n\n
\n\n \n Accept the converse argument.\n \n
\n\n This was very well answered. Candidates showed an understanding of the differences between ideal and real gases.\n
\n\n The speed of the tram is measured by detecting a beam of microwaves of wavelength 2.8 cm reflected from the rear of the tram as it moves away from the station. Predict the change in wavelength of the microwaves at the stationary microwave detector in the station.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n 1.2 nm ✓\n
\n\n Calculate the percentage error in the measured value of\n \n g\n \n .\n
\n\n [3]\n
\n\n error in\n \n m\n \n \n 1\n \n +\n \n m\n \n \n 2\n \n is 1 %\n \n \n OR\n \n \n error in\n \n m\n \n \n 1\n \n −\n \n m\n \n \n 2\n \n is 40 %\n \n \n OR\n \n \n error in\n \n a\n \n is 1 % ✔\n
\n\n adds percentage errors ✔\n
\n\n so error in g is 42 %\n \n \n OR\n \n \n 40 %\n \n \n OR\n \n \n 41.8 % ✔\n
\n\n \n Allow answer 0.42 or 0.4 or 0.418.\n \n
\n\n \n Award\n \n [0]\n \n for comparing the average value with a known value, e.g. 9.81 m s-2\n \n .\n
\n\n Atwoods machine a) is a quite straightforward question that tests the ability to propagate uncertainties through calculations. Almost all candidates proved the ability to add percentages or relative calculations, however, many weaker candidates failed in the percentage uncertainty when subtracting the two masses.\n
\n\n Show that the volume at C is 3.33 × 10\n \n −2\n \n m\n \n 3\n \n .\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Use of adiabatic formula «\n \n »\n \n ✓\n
\n\n \n × 2.00 × 10\n \n −3\n \n «= 3.333 × 10\n \n −2\n \n m\n \n 3\n \n » ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , working or answer to at least 4 SF must be seen.\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n p\n \n \n A\n \n \n V\n \n \n A\n \n =\n \n p\n \n \n B\n \n \n V\n \n \n B\n \n ✓\n
\n\n \n ✓\n
\n\n
\n\n \n \n ALTERNATIVE 3\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n n\n \n = 0.2 mol ✓\n
\n\n \n V\n \n \n C\n \n = (0.2 × 8.31 × 602) / 4 × 10\n \n 4\n \n ✓\n
\n\n Which statement about atomic nuclei is correct?\n
\n\n The density is…\n
\n\n
\n A. directly proportional to mass number.\n
\n B. inversely proportional to nuclear radius.\n
\n\n C. inversely proportional to volume.\n
\n\n D. constant for all nuclei.\n
\n\n [1]\n
\n\n D\n
\n\n Describe how thermal energy is distributed throughout the volume of the water in the pot.\n
\n\n [2]\n
\n\n By means of convection currents ✓\n
\n\n That arise due to density difference between hot and cold water ✓\n
\n\n \n A proton of velocity\n \n v\n \n enters a region of electric and magnetic fields. The proton is not deflected. An electron and an alpha particle enter the same region with velocity\n \n v\n \n . Which is correct about the paths of the electron and the alpha particle?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n \n Show that the electric field strength due to the point charge at the position of the electron is 3.4 × 10\n \n 8\n \n N C\n \n –1\n \n .\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n \n \n \n OR\n \n \n \n \n \n ✔\n \n \n
\n\n \n NOTE:\n \n Ignore any negative sign.\n \n \n
\n\n Which development in physics constituted a paradigm shift?\n
\n\n
\n\n A. The classification of variables into scalars and vectors\n
\n\n B. The determination of the velocity of light in different media\n
\n\n C. The equivalence of\n \n to\n \n when the mass of the system is constant\n
\n\n D. The equivalence of mass and energy\n
\n\n [1]\n
\n\n D\n
\n\n An electron is accelerated from rest through a potential difference\n \n V\n \n .\n
\n\n What is the maximum speed of the electron?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n The tram travels at\n \n v\n \n throughout the journey. Two trams are available so that one is returning to the lower station on another line while the other is travelling to the village. The journeys take the same time.\n
\n\n It takes 1.5 minutes to unload and 1.5 minutes to load each tram. Ignore the time taken to accelerate the tram at the beginning and end of the journey.\n
\n\n Estimate the maximum number of passengers that can be carried up to the village in one hour.\n
\n\n [4]\n
\n\n Time for run =\n \n s/v\n \n = 3000 ÷ 13.2 = 227 s ✓\n
\n\n 3 minutes loading = 180 s\n
\n\n So one trip = 407 s ✓\n
\n\n And there are 3600/407 trips per hour = 8.84 ✓\n
\n\n So 8\n \n complete\n \n trips with 75 = 600 passengers ✓\n
\n\n The black-body radiation curve of an object at 600 K is shown. The intensity units are arbitrary.\n
\n\n \n
\n What is the radiation curve of the same object at 450 K?\n
\n\n The original curve is shown with a dashed line.\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n The designers state that the energy transferred by the resistor every second is 15 J.\n
\n\n Calculate the current in the resistor.\n
\n\n [1]\n
\n\n \n I\n \n = «\n \n =» 1.9 «A» ✓\n
\n\n state and explain the net magnetic force acting on it due to the currents in PQ and TU.\n
\n\n [2]\n
\n\n The magnetic fields «due to currents in PQ and TU» are in opposite directions\n
\n \n \n OR\n \n \n
\n There are two «repulsive» forces in opposite directions ✓\n
\n Net force is zero ✓\n
\n\n \n Diagram not to scale\n \n
\n\n \n
\n A mass of 2.0 kg travelling at 5.0 m s\n \n −1\n \n collides with a mass of 4.0 kg travelling at 3.0 m s\n \n −1\n \n . The masses collide at right angles. They join and move together after the collision at\n \n θ\n \n to the original direction of the 2.0 kg mass.\n
\n\n What is\n \n θ\n \n ?\n
\n\n
\n A. 34°\n
\n B. 37°\n
\n\n C. 50°\n
\n\n D. 56°\n
\n\n [1]\n
\n\n C\n
\n\n \n Explain why some of this radiation is returned to the oceans from the atmosphere.\n \n
\n\n [3]\n
\n\n \n «most of the radiation emitted by the oceans is in the» infrared ✔\n
\n \n
\n \n «this radiation is» absorbed by greenhouse gases/named greenhouse gas in the atmosphere ✔\n
\n \n
\n \n «the gases» reradiate/re-emit ✔\n
\n \n
\n \n partly back towards oceans/in all directions/awareness that radiation in other directions is also present ✔\n \n
\n\n For many this was a well-rehearsed answer which succinctly scored full marks. For others too many vague terms were used. There was much talk about energy being trapped or reflected and the ozone layer was often included. The word ‘albedo’ was often written down with no indication of what it means and ‘the albedo effect also featured.\n
\n\n Three point charges of equal magnitude are placed at the vertices of an equilateral triangle. The signs of the charges are shown. Point P is equidistant from the vertices of the triangle. What is the direction of the resultant electric field at P?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n This question was very well answered by both HL and SL candidates, reflected in the high difficulty level for both papers.\n
\n\n Describe the photoelectric effect.\n
\n\n [2]\n
\n\n electrons are ejected from the surface of a metal\n \n ✓\n \n
\n\n after gaining energy from photons/electromagnetic radiation\n \n ✓\n \n
\n\n there is a minimum «threshold» energy/frequency\n
\n \n \n OR\n \n \n
\n maximum «threshold» wavelength\n \n ✓\n \n
\n A stone is thrown downwards from the edge of a cliff with a speed of 5.0 m s\n \n –1\n \n . It hits the ground 2.0 s later. What is the height of the cliff?\n
\n\n A. 20 m\n
\n\n B. 30 m\n
\n\n C. 40 m\n
\n\n D. 50 m\n
\n\n [1]\n
\n\n B\n
\n\n This question was well answered by the majority of candidates and had a high discrimination index.\n
\n\n Two blocks of masses\n \n m\n \n and 2\n \n m\n \n are travelling directly towards each other. Both are moving at the same constant speed\n \n v\n \n . The blocks collide and stick together.\n
\n\n What is the total momentum of the system before and after the collision?\n
\n\n \n
\n \n
\n [1]\n
\n\n A\n
\n\n Response A was the most common (correct) response, however response D was a significant distractor for candidates who took momentum to be a scalar quantity.\n
\n\n Discuss how the results of the experiment provide evidence for matter waves.\n
\n\n [2]\n
\n\n \n «\n \n \n the shape of the graph suggests that\n \n \n »\n \n \n electrons undergo diffraction\n \n \n «\n \n \n with carbon nuclei\n \n \n »\n \n \n ✓\n \n
\n\n \n only waves diffract\n \n \n ✓\n \n
\n\n This question was challenging for candidates many of whom seemed to have little idea of the experiment. Many answers discussed deflection, with the idea that forces between the electron and the nucleus causing it to deflect at a particular angle. This was often combined with the word interference to suggest evidence of matter waves. A number of answers described a demonstration the candidates remembered seeing so answers talked about fuzzy green rings.\n
\n\n A charged rod is brought near an initially neutral metal sphere without touching it.\n
\n\n When the sphere is grounded (earthed), there is an electric current for a short time from the sphere to the ground.\n
\n\n \n
\n The ground connection is then removed.\n
\n\n What are the charge on the rod and the charge induced on the sphere when the connection is removed?\n
\n
\n
\n \n
\n [1]\n
\n\n C\n
\n\n A car on a road follows a horizontal circular path at a constant speed. What is the direction of the net force acting on the car and the direction of the instantaneous velocity of the car?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n Three point charges, +Q, +Q and −Q, are fixed at the three corners of a square.\n
\n\n What is the direction of the electric field at the fourth corner?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n Calculate the work done to bring a small charge\n \n q\n \n from infinity to point C.\n
\n\n Data given:\n
\n\n \n Q\n \n = 2.0 × 10\n \n −3\n \n C,\n
\n\n \n q\n \n = 4.0 × 10\n \n −9\n \n C\n
\n\n \n D\n \n = 1.2 m\n
\n\n [2]\n
\n\n \n V\n \n «= 2 ×\n \n » = 6.0 × 10\n \n 7\n \n «V» ✓\n
\n\n \n W\n \n = «qV = 6.0 × 10\n \n 7\n \n × 4.0 × 10\n \n −9\n \n =» 0.24 «J» ✓\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n \n The resistance of component X decreases when the intensity of light incident on it increases. X is connected in series with a cell of negligible internal resistance and a resistor of fixed resistance. The ammeter and voltmeter are ideal.\n \n \n \n
\n \n \n
\n \n \n \n
\n \n \n What is the change in the reading on the ammeter and the change in the reading on the voltmeter when the light incident on X is increased?\n \n \n
\n\n \n \n \n \n \n
\n [1]\n
\n\n A\n
\n\n \n An object of mass\n \n m\n \n makes\n \n n\n \n revolutions per second around a circle of radius\n \n r\n \n at a constant speed. What is the kinetic energy of the object?\n \n
\n\n \n A. 0\n
\n \n
\n \n B.\n \n
\n \n
\n \n C.\n \n
\n \n
\n \n D.\n \n
\n \n
\n [1]\n
\n\n C\n
\n\n Which graph shows the variation with time\n \n t\n \n of the kinetic energy (KE) of an object undergoing simple harmonic motion (shm) of period T?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n State what is meant by a transverse wave.\n
\n\n [1]\n
\n\n «A wave where the» displacement of particles/oscillations of particles/movement of particles/vibrations of particles is perpendicular/normal to the direction of energy transfer/wave travel/wave velocity/wave movement/wave propagation ✓\n
\n\n
\n\n \n Allow medium, material, water, molecules, or atoms for particles.\n \n
\n\n Deduce the unit of μ in terms of fundamental SI units.\n
\n\n [1]\n
\n\n [μ] = «\n \n » kg × m\n \n −1\n \n
\n\n
\n\n \n Accept kg/m.\n \n
\n\n \n Do\n \n not\n \n accept g m\n \n −1\n \n .\n \n
\n\n Estimate the initial rate of the change of the temperature of the water in the bottle. State your answer in K s\n \n −1\n \n . The specific heat capacity of water is 4200 J kg\n \n −1\n \n K\n \n −1\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «K s\n \n −1\n \n » ✓\n
\n\n The coil of a direct current electric motor is turning with a period\n \n T\n \n . At\n \n t\n \n = 0 the coil is in the position shown in the diagram. Assume the magnetic field is uniform across the coil.\n
\n\n \n
\n Which graph shows the variation with time of the force exerted on section XY of the coil during one complete turn?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Has a negative discrimination index with over 80% of candidates choosing the incorrect answer. The difficulty index is also low. The question states that it is about a direct current electric motor, suggesting that C and D are incorrect so by choosing them it would seem that some candidates are confusing an electric motor with a generator.\n
\n\n Three lamps (X, Y and Z) are connected as shown in the circuit. The emf of the cell is 20 V. The internal resistance of the cell is negligible. The power dissipated by X, Y and Z is 10 W, 20 W and 20 W respectively.\n
\n\n \n
\n What is the voltage across Lamp X and Lamp Y?\n
\n\n
\n| \n | \n\n \n Lamp X\n \n | \n\n \n Lamp Y\n \n | \n
| \n A.\n | \n\n 16 V\n | \n\n 4 V\n | \n
| \n B.\n | \n\n 4 V\n | \n\n 16 V\n | \n
| \n C.\n | \n\n 4 V\n | \n\n 8 V\n | \n
| \n D.\n | \n\n 16 V\n | \n\n 16 V\n | \n
\n
\n\n [1]\n
\n\n B\n
\n\n The temperature of the gas in the container is increased.\n
\n\n Explain, using the kinetic theory, how this change leads to a change in pressure in the container.\n
\n\n [4]\n
\n\n increased temperature means increased average KE and hence increased average translational speed ✓\n
\n\n This increases the momentum transfer at the walls for each collision /\n \n mv\n \n is greater per collision ✓\n
\n\n This increases the frequency of collisions at the walls / particles cover the distance between walls more quickly ✓\n
\n\n Ideas that\n \n AND\n \n (can be in words) so that force increases and pressure\n \n increases\n \n ✓\n
\n\n A ball undergoes an elastic collision with a vertical wall. Which of the following is equal to zero?\n
\n\n A. The change of the magnitude of linear momentum of the ball\n
\n\n B. The magnitude of the change of linear momentum of the ball\n
\n\n C. The rate of change of linear momentum of the ball\n
\n\n D. The impulse of the force on the ball\n
\n\n [1]\n
\n\n A\n
\n\n increasing the distance between the diffraction grating and the screen.\n
\n\n [1]\n
\n\n no change\n \n ✓\n \n
\n\n A star is on the main sequence.\n
\n\n What are the most abundant element(s) in the core of the star and in the outer layer of the star?\n
\n\n
\n| \n | \n\n \n Most abundant element(s) in the core\n \n | \n\n \n Most abundant element(s) in the outer layer\n \n | \n
| \n A.\n | \n\n Helium and lithium\n | \n\n Hydrogen\n | \n
| \n B.\n | \n\n Hydrogen\n | \n\n Helium\n | \n
| \n C.\n | \n\n Hydrogen and helium\n | \n\n Hydrogen and lithium\n | \n
| \n D.\n | \n\n Hydrogen\n | \n\n Helium and beryllium\n | \n
\n [1]\n
\n\n B\n
\n\n What is the likely evolutionary outcome for a star with the same mass as the Sun?\n
\n\n
\n A. main sequence star → red giant → supernova → white dwarf\n
\n B. main sequence star → red giant → planetary nebula → white dwarf\n
\n\n C. main sequence star → super giant → supernova → neutron star\n
\n\n D. main sequence star → super giant → planetary nebula → black hole\n
\n\n [1]\n
\n\n B\n
\n\n Outline why this force does no work on the Moon.\n
\n\n [1]\n
\n\n the force/field and the velocity/displacement are at 90° to each other\n \n \n OR\n \n \n there is no change in GPE of the moon ✔\n
\n\n \n Award\n \n [0]\n \n for any mention of no net force on the satellite.\n \n
\n\n \n Do not accept acceleration is perpendicular to velocity.\n \n
\n\n Some candidates connected the idea that the gravitational force is perpendicular to the velocity (and hence the displacement) for the mark. It was also allowed to discuss that there is no change in gravitational potential energy, so therefore no work was being done. It was not acceptable to simply state that the net displacement over one full orbit is zero. Unfortunately, some candidates suggested that there is no net force on the moon so there is no work done, or that the moon is so much smaller so no work could be done on it.\n
\n\n Determine\n \n .\n
\n\n [2]\n
\n\n Work using\n \n g\n \n ∝\n \n ✓\n
\n\n \n = 0.75 ✓\n
\n\n \n Suggest whether the data are consistent with the theoretical prediction.\n \n
\n\n [2]\n
\n\n \n «theory suggests»\n \n \n \n is proportional to\n \n \n \n ✓\n \n
\n\n \n
\n \n \n graph/line of best fit is straight/linear «so yes»\n
\n \n \n \n \n OR\n \n \n
\n \n \n graph/line of best fit passes through the origin «so yes»\n \n \n ✓\n \n
\n
\n\n \n \n MP1: Accept ‘linear’\n
\n \n \n
\n \n \n MP2 do not award if there is any contradiction\n
\n eg: graph not proportional, does not pass through origin.\n \n \n
\n Many students obtained full marks here although a significant number did not acknowledge that the graph was through the origin and lost a mark.\n
\n\n A cell of negligible internal resistance is connected to three identical resistors. The current in the cell is 3.0 A.\n
\n\n \n
\n The resistors are now arranged in series.\n
\n\n What is the new current in the cell?\n
\n\n
\n A. 1.0 A\n
\n B. 1.5 A\n
\n\n C. 3.0 A\n
\n\n D. 9.0 A\n
\n\n [1]\n
\n\n B\n
\n\n This question was answered well and discriminated well, especially at HL. The resistance of the connection doubles (from 1.5\n \n R\n \n to 3\n \n R\n \n ) therefore the current is halved.\n
\n\n \n The student has plotted error bars for the potential difference. Outline why no error bars are shown for the current.\n \n
\n\n [1]\n
\n\n \n Δ\n \n I\n \n is too small to be shown/seen\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n Error bar of negligible size compared to error bar in\n \n V\n \n ✔\n \n
\n\n Almost all candidates realised that the uncertainty in I was too small to be shown. A common mistake was to mention that since I is the independent variable the uncertainty is negligible.\n
\n\n Explain why star B has a greater surface area than star A.\n
\n\n [2]\n
\n\n stars have same/similar\n \n L\n \n \n \n AND\n \n \n star B has lower\n \n T\n \n ✓\n
\n\n correct reference to luminosity formula (\n \n L\n \n α\n \n AT\n \n \n 4\n \n ) ✓\n
\n\n
\n\n \n \n MP1\n \n Allow reverse argument i.e., star A has higher T\n \n
\n\n State the phase difference between the waves at V and Y.\n
\n\n [1]\n
\n\n 0\n \n \n OR\n \n \n 2\n \n π\n \n \n \n OR\n \n \n 360°\n \n ✓\n \n
\n\n
\n\n An object performs simple harmonic motion (shm). The graph shows how the velocity\n \n v\n \n of the object varies with time\n \n t\n \n .\n
\n\n \n
\n The displacement of the object is\n \n x\n \n and its acceleration is\n \n a\n \n . What is the variation of\n \n x\n \n with\n \n t\n \n and the variation of\n \n a\n \n with\n \n t\n \n ?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n A person stands in an elevator (lift). The total mass of the person and the elevator is 800 kg. The elevator accelerates upward at 2.0 m s\n \n −2\n \n .\n
\n\n \n
\n What is the tension in the cable?\n
\n\n
\n A. 1.6 kN\n
\n B. 6.4 kN\n
\n\n C. 8.0 kN\n
\n\n D. 9.6 kN\n
\n\n [1]\n
\n\n D\n
\n\n A fixed mass of an ideal gas has a volume of\n \n , a pressure of\n \n p\n \n and a temperature of\n \n . The gas is compressed to the volume of\n \n and its pressure increases to 12\n \n p\n \n . What is the new temperature of the gas?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Determine the fractional number of throws for which the three most likely macrostates occur.\n
\n\n
\n\n [3]\n
\n\n Recognises that 4 heads and 6 tails also required ✓\n
\n\n Total number of microstates = 672 ✓\n
\n\n Fractional number = 672/1024 = 0.66 ✓\n
\n\n
\n\n \n Allow ecf for MP3\n \n
\n\n Planets X and Y orbit the same star.\n
\n\n The average distance between planet X and the star is five times greater than the average distance between planet Y and the star.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Describe, in terms of electron flow, how the smaller sphere becomes charged.\n
\n\n [1]\n
\n\n electrons leave the small sphere «making it positively charged» ✓\n
\n\n Calculate the percentage uncertainty in the value of\n \n A\n \n .\n
\n\n [2]\n
\n\n attempt to calculate fractional uncertainty in either\n \n a\n \n or\n \n b\n \n [0.0357, 0.0167] ✓\n
\n\n 0.0357 + 0.0167 = 0.05 = 5% ✓\n
\n\n An object of mass\n \n released from rest near the surface of a planet has an initial acceleration\n \n . What is the gravitational field strength near the surface of the planet?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Two currents of 3 A and 1 A are established in the same direction through two parallel straight wires R and S.\n
\n\n \n
\n What is correct about the magnetic forces acting on each wire?\n
\n\n A. Both wires exert equal magnitude attractive forces on each other.\n
\n\n B. Both wires exert equal magnitude repulsive forces on each other.\n
\n\n C. Wire R exerts a larger magnitude attractive force on wire S.\n
\n\n D. Wire R exerts a larger magnitude repulsive force on wire S.\n
\n\n [1]\n
\n\n A\n
\n\n This question had the lowest difficulty index on the HL paper, with roughly 10 % of candidates selecting response A. Responses C and D were roughly equally common candidate answers, with students not recognizing the applicability of Newton’s 3rd law.\n
\n\n Calculate, in m s\n \n −1\n \n , the maximum velocity of vibration of point P when it is vibrating with a frequency of 195 Hz.\n
\n\n [2]\n
\n\n max velocity occurs at x = 0\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n The graph shows the variation of the displacement of a wave with distance along the wave.\n
\n \n
\n \n The wave speed is 0.50 m s\n \n -1\n \n .\n \n
\n\n \n \n \n
\n \n \n What is the period of the wave?\n
\n \n \n
\n \n \n A. 0.33 s\n
\n \n \n
\n \n \n B. 1.5 s\n
\n \n \n
\n \n \n C. 3.0 s\n
\n \n \n
\n \n \n D. 6.0 s\n \n \n
\n\n [1]\n
\n\n C\n
\n\n Calculate, in nm,\n \n .\n
\n\n [3]\n
\n\n \n s\n \n =\n \n \n \n OR\n \n \n = 0.0188 «m» ✓\n
\n\n use of\n \n ✓\n
\n\n 450 «nm» ✓\n
\n\n A car engine has a useful power output of 20 kW and an efficiency of 50 %. The engine consumes 1 × 10\n \n −5\n \n m\n \n 3\n \n of fuel every second. What is the energy density of the fuel?\n
\n\n
\n A. 2 MJ m\n \n −3\n \n
\n B. 4 MJ m\n \n −3\n \n
\n\n C. 2 GJ m\n \n −3\n \n
\n\n D. 4 GJ m\n \n −3\n \n
\n\n [1]\n
\n\n D\n
\n\n Two samples of a gas are kept in separate containers. The molecules of each sample have the same average translational speed, but the samples have a different density.\n
\n\n What is correct about the pressure and the temperature of the samples, as compared to each other?\n
\n\n
\n| \n | \n\n \n Pressure\n \n | \n\n \n Temperature\n \n | \n
| \n A.\n | \n\n same\n | \n\n same\n | \n
| \n B.\n | \n\n same\n | \n\n different\n | \n
| \n C.\n | \n\n different\n | \n\n same\n | \n
| \n D.\n | \n\n different\n | \n\n different\n | \n
\n [1]\n
\n\n C\n
\n\n Calculate the speed of waves on the string.\n
\n\n [2]\n
\n\n wavelength\n \n «m» ✓\n
\n\n speed\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from incorrect wavelength.\n \n
\n\n This was well answered, particularly MP1 to determine the wavelength, although several candidates misinterpreted the unit of time and obtained a very small value for the velocity of the wave.\n
\n\n A negative charge Q is to be moved within an electric field E, to equidistant points from its position, as shown.\n
\n\n Which path requires the most work done?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n The most common answer was A, suggesting that students missed the prompt that Q is a negative charge.\n
\n\n Draw an arrow on the diagram to represent the direction of the acceleration of the satellite.\n
\n\n [1]\n
\n\n arrow normal to the orbit towards the Earth ✓\n
\n\n Two parallel wires carry equal currents in the same direction out of the paper. Which diagram shows the magnetic field surrounding the wires?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n State\n \n two\n \n assumptions of the kinetic model of an ideal gas that refer to intermolecular collisions.\n
\n\n [2]\n
\n\n The collisions are elastic ✓\n
\n\n The time for a collision is much shorter than the time between collisions ✓\n
\n\n The intermolecular forces are only present during collisions ✓\n
\n\n one variable that must be controlled,\n
\n\n [1]\n
\n\n mass\n \n \n OR\n \n \n diameter\n \n \n OR\n \n \n material of bob\n \n \n OR\n \n \n « initial » amplitude/angle ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow statements about rulers, stopwatches, string, number of oscillations, constant gravity.\n \n
\n\n Estimate the specific heat capacity of the oil in its liquid phase. State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n \n \n \n OR\n \n \n \n ✓\n
\n\n \n \n \n OR\n \n \n \n ✓\n
\n\n \n \n
\n Allow any appropriate unit that is\n \n \n \n
\n Adjacent minima are separated by a distance of 0.12 m. Calculate\n \n \n \n .\n
\n\n [2]\n
\n\n wavelength = 0.24 «m» ✓\n
\n\n \n = «\n \n =» 1.4 «kHz»\n \n \n OR\n \n \n 1400 «Hz» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n A star has a radius 13 times that of the Sun and a luminosity that is 400 000 times that of the Sun.\n
\n\n The surface temperature of the Sun is 5700 K.\n
\n\n What is the surface temperature of the star?\n
\n\n
\n A. 4.0 x 10\n \n 4\n \n K\n
\n B. 7.6 x 10\n \n 4\n \n K\n
\n\n C. 1.0 x 10\n \n 5\n \n K\n
\n\n D. 1.4 x 10\n \n 7\n \n K\n
\n\n [1]\n
\n\n A\n
\n\n \n The lines of the minimum and maximum gradient are shown.\n \n
\n\n \n \n \n
\n \n \n Estimate the absolute uncertainty in\n \n a\n \n .\n \n \n
\n\n [2]\n
\n\n \n «s» ±0.001 «s»\n \n \n AND\n \n \n \n «s» ±0.001 «s» ✔\n
\n\n «\n \n » 0.003 «s» ✔\n
\n\n The concept of potential is also used in the context of gravitational fields. Suggest why scientists developed a common terminology to describe different types of fields.\n
\n\n [1]\n
\n\n \n to highlight similarities between\n \n \n «\n \n \n different\n \n \n »\n \n \n fields\n \n \n ✓\n \n
\n\n This was generally well answered with only a small number of answers suggesting greater international cooperation.\n
\n\n The resistor has a cross-sectional area of 9.6 × 10\n \n −6\n \n m\n \n 2\n \n .\n
\n\n Show that a resistor made from carbon fibre will be suitable for the pad.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n (Calculation of length)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n l\n \n = 1.3 − 1.4 «m» ✓\n
\n \n \n ALTERNATIVE 2\n \n \n (Calculation of area)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n A\n \n = 8.3 − 9.5 × 10\n \n −6\n \n «m\n \n 2\n \n » ✓\n
\n\n \n \n ALTERNATIVE 3\n \n \n (Calculation of resistance)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n R\n \n = 3.6 − 4.2 «Ω» ✓\n
\n\n \n \n ALTERNATIVE 4\n \n \n (Calculation of resistivity)\n
\n Use of\n \n ✓\n
\n \n \n \n = 3.2 × 10\n \n −5\n \n «Ω m» ✓\n
\n\n Read off from graph 260 – 280 K ✓\n
\n\n Two charges\n \n Q\n \n \n 1\n \n and\n \n Q\n \n \n 2\n \n , each equal to 2 nC, are separated by a distance 3 m in a vacuum. What is the electric force on\n \n Q\n \n \n 2\n \n and the electric field due to\n \n Q\n \n \n 1\n \n at the position of\n \n Q\n \n \n 2\n \n ?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n An ion moves in a circle in a uniform magnetic field. Which single change would increase the radius of the circular path?\n
\n\n
\n A. Decreasing the speed of the ion\n
\n B. Increasing the charge of the ion\n
\n\n C. Increasing the mass of the ion\n
\n\n D. Increasing the strength of the magnetic field\n
\n\n [1]\n
\n\n C\n
\n\n Calculate the percentage uncertainty in the value of\n \n A\n \n .\n
\n\n [2]\n
\n\n attempt to calculate fractional uncertainty in either\n \n a\n \n or\n \n b\n \n [0.0357, 0.0167] ✓\n
\n\n 0.0357 + 0.0167 = 0.05 = 5 % ✓\n
\n\n State and explain the wavelength of the sound measured at M.\n
\n\n [2]\n
\n\n wavelength = 26 cm ✓\n
\n\n
\n peak to peak distance is the path difference which is one wavelength\n
\n \n \n OR\n \n \n
\n\n this is the distance B moves to be back in phase «with A» ✓\n
\n\n
\n\n \n Allow 25 – 27 cm for\n \n MP1\n \n .\n \n
\n\n Many candidates recognized that the wavelength was 26 cm, but the explanations were lacking the details about what information the graph was actually providing. Examiners were looking for a connection back to path difference, and not simply a description of peak-to-peak distance on the graph. Some candidates did not state a wavelength at all, and instead simply discussed the concept of wavelength or suggested that the wavelength was constant.\n
\n\n State what will happen to the width of the primary maxima.\n
\n\n [1]\n
\n\n decreases ✓\n
\n\n Describe the photoelectric effect.\n
\n\n [2]\n
\n\n electrons are ejected from the surface of a metal\n \n ✓\n \n
\n\n after gaining energy from photons/electromagnetic radiation\n \n ✓\n \n
\n\n there is a minimum «threshold» energy/frequency\n
\n \n \n OR\n \n \n
\n maximum «threshold» wavelength\n \n ✓\n \n
\n The heater is removed and a mass of 0.30 kg of pasta at −10 °C is added to the boiling water.\n
\n\n Determine the equilibrium temperature of the pasta and water after the pasta is added. Other heat transfers are negligible.\n
\n\n Specific heat capacity of pasta = 1.8 kJ kg\n \n −1\n \n K\n \n −1\n \n
\n Specific heat capacity of water = 4.2 kJ kg\n \n −1\n \n K\n \n −1\n \n
\n [3]\n
\n\n use of mcΔT\n \n ✓\n \n
\n\n 0.86 × 4200 × (100 –\n \n T\n \n ) = 0.3 × 1800 × (\n \n T\n \n +10)\n \n ✓\n \n
\n\n \n T\n \n \n eq\n \n = 85.69«°C» ≅ 86«°C»\n \n ✓\n \n
\n\n \n Accept T\n \n eq\n \n in Kelvin (359 K).\n \n
\n\n Draw the line of best fit for these data.\n
\n\n [1]\n
\n\n straight line through all error bars ✓\n
\n\n Outline, without calculation, the change to the time period of the system for the model represented by graph B when\n \n is large.\n
\n\n [2]\n
\n\n time period increases ✓\n
\n\n
\n\n because average ω «for whole cycle» is smaller\n
\n\n \n \n OR\n \n \n
\n\n slope / acceleration / force at large x is smaller\n
\n\n \n \n OR\n \n \n
\n\n area under graph B is smaller so average speed is smaller. ✓\n
\n\n Many candidates recognized that the time period would increase for B, and some were able to give a valid reason based on the difference between the motion of B and the motion of A. It should be noted that the prompt specified \"without calculation\", so candidates who simply attempted to calculate the time period of B did not receive marks.\n
\n\n State the principal energy change in nuclear fission.\n
\n\n [1]\n
\n\n Mass-energy «of uranium» into kinetic energy of fission products ✓\n
\n\n Explain why the received intensity varies between maximum and minimum values.\n
\n\n [3]\n
\n\n movement of B means that path distance is different « between BM and AM »\n
\n \n \n OR\n \n \n
\n movement of B creates a path difference «between BM and AM» ✓\n
\n interference\n
\n \n \n OR\n \n \n
\n superposition «of waves» ✓\n
\n maximum when waves arrive in phase / path difference = n x lambda\n
\n \n \n OR\n \n \n
\n minimum when waves arrive «180° or\n \n » out of phase / path difference = (n+½) x lambda ✓\n
\n This was an \"explain\" questions, so examiners were looking for a clear discussion of the movement of speaker B creating a changing path difference between B and the microphone and A and the microphone. This path difference would lead to interference, and the examiners were looking for a connection between specific phase differences or path differences for maxima or minima. Some candidates were able to discuss basic concepts of interference (e.g. \"there is constructive and destructive interference\"), but failed to make clear connections between the physical situation and the given graph. A very common mistake candidates made was to think the question was about intensity and to therefore describe the decrease in peak height of the maxima on the graph. Another common mistake was to approach this as a Doppler question and to attempt to answer it based on the frequency difference of B.\n
\n\n P is a point in a uniform electric field.\n
\n\n What is the direction in which the electric potential increases at P?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Show that the apparent brightness\n \n , where\n \n is the distance of the object from Earth,\n \n is the surface temperature of the object and\n \n is the surface area of the object.\n
\n\n [1]\n
\n\n substitution of\n \n into\n \n giving\n \n
\n\n
\n\n \n \n Removal of constants\n \n and\n \n is optional\n \n \n
\n\n State why the experiment is repeated with different values of\n \n .\n
\n\n [1]\n
\n\n \n In order to draw a graph « of\n \n \n \n \n \n versus\n \n »\n
\n \n \n \n \n OR\n \n \n
\n \n
\n \n to confirm proportionality between «\n \n \n \n \n \n and\n \n \n \n »\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n to confirm relationship between «\n \n \n \n \n \n and\n \n \n \n »\n
\n \n
\n \n \n \n OR\n \n \n \n \n
\n \n
\n \n because\n \n \n W\n \n \n is the independent variable in the experiment\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Most candidates scored. Different wording was used to express the aim of confirming the relationship.\n
\n\n Draw the forces acting on the oil drop, ignoring the buoyancy force.\n
\n\n \n
\n [2]\n
\n\n Weight vertically down\n \n \n AND\n \n \n electric force vertically up ✓\n
\n\n Of equal length «by eye» ✓\n
\n\n Explain the changes to the rotational kinetic energy in the person-turntable system.\n
\n\n [2]\n
\n\n \n the rotational kinetic energy has increased\n \n \n ✓\n \n
\n\n \n energy is provided by the person doing work\n \n \n «\n \n \n flipping the wheel\n \n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Explain why the work done by the gas during the isothermal expansion AB is less than the work done on the gas during the adiabatic compression BC.\n
\n\n [1]\n
\n\n area under curve AB is less than area under curve BC ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from part\n \n (b)\n \n \n
\n\n White dwarfs with similar volumes to each other are shown on the HR diagram.\n
\n\n Sketch, on the HR diagram, to show the possible positions of other white dwarf stars with similar volumes to those marked on the HR diagram.\n
\n\n [2]\n
\n\n Any evidence of correct identification that three dots bottom left represent white dwarfs ✓\n
\n\n line passing through all 3 white dwarfs\n \n \n OR\n \n \n line continuing from 3 white dwarfs with approximately same gradient, in either direction ✓\n
\n\n
\n\n \n Award\n \n MP2\n \n if no line drawn through the three dots but just beyond them in either direction\n \n
\n\n Explain a possible reason for the systematic error.\n
\n\n [1]\n
\n\n mass of tray of weights neglected/friction at pulley/friction at slider/thickness of slider/zero off-set error ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow vague answers like friction neglected / error in length measurement.\n \n
\n\n Describe\n \n one\n \n other method by which significant amounts of energy can be transferred from the pipe to the surroundings.\n
\n\n [2]\n
\n\n convection «is likely to be a significant loss» ✓\n
\n\n
\n «due to reduction in density of air near pipe surface» hot air rises «and is replaced by cooler air from elsewhere»\n
\n \n \n OR\n \n \n
\n\n «due to» conduction «of heat or thermal energy» from pipe to air ✓\n
\n\n A few candidates recognized that convection was the third source of heat loss, although few managed to describe the mechanism of convection properly for MP2. Some candidates did not read the question carefully and instead wrote about methods to increase the rate of heat loss (such as removing more insulation or decreasing the temperature of the environment).\n
\n\n \n The tension in a horizontal spring is directly proportional to the extension of the spring. The energy stored in the spring at extension\n \n is\n \n . What is the work done by the spring when its extension changes from\n \n to\n \n ?\n \n
\n\n \n A.\n \n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The radius of the dwarf planet Pluto is 1.19 x 10\n \n 6\n \n m. The acceleration due to gravity at its surface is 0.617 m s\n \n −2\n \n .\n
\n\n Determine the escape speed for an object at the surface of Pluto.\n
\n\n [4]\n
\n\n \n AND\n \n seen ✓\n
\n\n \n ✓\n
\n\n Leading to\n \n ✓\n
\n\n 1.2 km s\n \n −1\n \n ✓\n \n \n
\n\n A sound wave has a frequency of 1.0 kHz and a wavelength of 0.33 m. What is the distance travelled by the wave in 2.0 ms and the nature of the wave?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n Sketch, on the axes, a graph to show the variation with time of the magnitude of the emf induced in the loop.\n
\n\n \n
\n [1]\n
\n\n \n
\n shape as above ✓\n
\n\n
\n\n \n Vertical lines not necessary to score.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n (b)(i)\n \n .\n \n
\n\n A positive point charge of magnitude 1.0 μC and a point charge\n \n q\n \n are separated by a distance\n \n d\n \n .\n
\n\n \n
\n An electron is placed at a distance\n \n d\n \n from the +1.0 μC charge. The electric force on the electron is zero.\n
\n\n What is\n \n q\n \n ?\n
\n\n
\n A. −4.0 μC\n
\n B. −2.0 μC\n
\n\n C. 2.0 μC\n
\n\n D. 4.0 μC\n
\n\n [1]\n
\n\n A\n
\n\n Explain why a centripetal force is needed for the planet to be in a circular orbit.\n
\n\n [2]\n
\n\n «circular motion» involves a changing velocity\n \n ✓\n \n
\n\n «Tangential velocity» is «always» perpendicular to centripetal force/acceleration\n \n ✓\n \n
\n\n there must be a force/acceleration towards centre/star\n \n ✓\n \n
\n\n without a centripetal force the planet will move in a straight line\n \n ✓\n \n
\n\n Sketch, on the axes, a graph to show the variation with time of the magnitude of the emf induced in the loop.\n
\n\n \n
\n [1]\n
\n\n \n
\n shape as above ✓\n
\n\n
\n\n \n Vertical lines not necessary to score.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n (b)(i)\n \n .\n \n
\n\n \n one\n \n advantage of energy production by nuclear fusion compared to nuclear fission.\n
\n\n [1]\n
\n\n Plentiful fuel supplies\n \n \n OR\n \n \n larger specific energy\n \n \n OR\n \n \n larger energy density\n \n \n OR\n \n \n little or no «major radioactive» waste products ✓\n
\n\n
\n\n \n Allow descriptions such as “more energy per unit mass” or “more energy per unit volume”\n \n
\n\n Outline whether your answer to (a) is likely to overestimate or underestimate the power input.\n
\n\n [2]\n
\n\n Underestimate / more energy or power required ✓\n
\n\n because energy transferred as heat / thermal energy is lost «to surroundings or electrical components» ✓\n
\n\n
\n\n \n Do not allow general term “energy” or “power” for\n \n MP2\n \n .\n \n
\n\n Many candidates recognized that this was an underestimate of the total energy but failed to provide an adequate reason. Many gave generic responses (such as \"some power will be lost\"/not 100% efficient) without discussing the specific form of energy lost (e.g. heat energy).\n
\n\n Satellite X orbits a planet with orbital radius\n \n R\n \n . Satellite Y orbits the same planet with orbital radius 2\n \n R\n \n . Satellites X and Y have the same mass.\n
\n\n What is the ratio\n \n \n \n ?\n
\n\n A.\n \n \n \n
\n\n B.\n \n \n \n
\n\n C. 2\n
\n\n D. 4\n
\n\n [1]\n
\n\n D\n
\n\n There is an advantage and a disadvantage in using two masses that are almost equal.\n
\n\n State and explain the disadvantage with reference to your answer to (a)(ii).\n
\n\n [2]\n
\n\n the percentage error in the difference of the masses is large ✔\n
\n\n leading to a large percentage error/uncertainty in g/of the experiment ✔\n
\n\n \n Do not accept ideas related to the mass/moment of inertia of the pulley.\n \n
\n\n In part ii) many were able to appreciate that the resultant percentage error in “g” was relatively large however linking this with what caused the large uncertainty (that is, the high % error from the small difference in masses) proved more challenging.\n
\n\n \n A liquid of mass\n \n m\n \n and specific heat capacity\n \n c\n \n cools. The rate of change of the temperature of the liquid is\n \n k\n \n . What is the rate at which thermal energy is transferred from the liquid?\n \n
\n\n \n A.\n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n kmc\n \n \n
\n\n [1]\n
\n\n D\n
\n\n \n What is the function of the moderator in a thermal nuclear fission reactor?\n \n
\n\n \n A. To decrease the kinetic energy of neutrons emitted from fission reactions\n
\n \n
\n \n B. To increase the kinetic energy of neutrons emitted from fission reactions\n
\n \n
\n \n C. To decrease the overall number of neutrons available for fission\n
\n \n
\n \n D. To increase the overall number of neutrons available for fission\n \n
\n\n [1]\n
\n\n A\n
\n\n Suggest one problem that is faced in dealing with the waste from nuclear fission reactors. Go on to outline how this problem is overcome.\n
\n\n [2]\n
\n\n Waste is very hot …\n
\n\n … So has to be placed in cooling ponds to transfer the (thermal) energy away ✓\n
\n\n
\n\n \n OR\n \n
\n\n Waste is very radioactive … ✓\n
\n\n … So has to be placed in cooling ponds to absorb this radiation\n
\n\n \n OR\n \n
\n\n … So has to be handled remotely\n
\n\n \n OR\n \n
\n\n … So has to be transported in crash resistant casings / stored on site ✓\n
\n\n
\n\n \n OR\n \n
\n\n Waste will be radioactive for thousands of years … ✓\n
\n\n … So storage needs to be (eventually) in geologically stable areas ✓\n
\n\n State\n \n one\n \n source of the radioactive waste products from nuclear fission reactions.\n
\n\n [1]\n
\n\n Fission fragments from the fuel rods\n
\n\n \n OR\n \n activated materials in (e.g.) fuel rod casings\n
\n\n \n OR\n \n nuclei formed by neutron activation from U-235\n
\n\n \n OR\n \n stated products, e.g. Pu, U-236 etc. ✓\n
\n\n State and explain, using your diagram, why a force acts on B due to A in the plane of the paper.\n
\n\n [3]\n
\n\n B lies in magnetic field of A OWTTE ✓\n
\n\n Explained use of appropriate rule together with drawn indication of rule operating in this case ✓\n
\n\n To show that force on B is to left and in plane of paper ✓\n
\n \n \n OR\n
\n \n \n Magnetic field lines of B merge with those of A to give combined field line pattern ✓\n
\n Sketch of combined pattern to show null point somewhere on line between wires. ✓\n
\n\n Wires will move to reduce stored energy and this is achieved by moving together so force on B is to left ✓\n
\n\n Calculate\n \n for a speed of 0.80\n \n c\n \n .\n
\n\n [1]\n
\n\n \n ✓\n
\n\n \n determine the thermal energy removed from the system.\n \n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n work done\n \n \n ✔\n \n
\n\n change in internal energy\n \n
\n \n \n OR\n
\n \n \n \n \n \n \n \n \n ✔\n \n
\n thermal energy removed\n \n
\n \n \n OR\n
\n \n \n \n \n \n \n \n \n ✔\n \n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n \n ✔\n \n
\n\n thermal energy removed\n \n \n ✔\n \n
\n\n \n \n \n \n ✔\n \n
\n\n The input power of an electric motor is 200 W. It is used to raise a mass of 10 kg at constant speed.\n
\n If the efficiency of the motor is 40 %, through what height will the mass be raised in 1 second?\n
\n
\n A. 0.5 m\n
\n B. 0.8 m\n
\n\n C. 1.2 m\n
\n\n D. 2.0 m\n
\n\n [1]\n
\n\n B\n
\n\n A block of mass 2.0 kg accelerates from a speed of 15 m s\n \n −1\n \n to a speed of 20 m s\n \n −1\n \n without changing its direction.\n
\n\n What impulse acts on the block?\n
\n\n
\n A. 2.5 N s\n
\n B. 5.0 N s\n
\n\n C. 10 N s\n
\n\n D. 17.5 N s\n
\n\n [1]\n
\n\n C\n
\n\n Show that the speed of the loop is 20 cm s\n \n −1\n \n .\n
\n\n [1]\n
\n\n \n ✓\n
\n\n An object of mass\n \n strikes a vertical wall horizontally at speed\n \n . The object rebounds from the wall horizontally at speed\n \n .\n
\n\n What is the magnitude of the change in the momentum of the object?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n State the conclusion that can be drawn from the existence of these two routes.\n
\n\n [1]\n
\n\n evidence for nuclear energy levels ✓\n
\n\n \n The molar mass of helium is 4.0 g mol\n \n -1\n \n . Show that the mass of a helium atom is 6.6 × 10\n \n -27\n \n kg.\n \n
\n\n [1]\n
\n\n \n \n \n \n «kg»\n \n \n \n
\n \n \n
\n \n \n \n OR\n \n
\n \n \n
\n \n 6.64\n \n ×\n \n 10\n \n \n \n −27\n \n \n \n \n \n «kg»\n \n \n \n ✔\n \n \n
\n\n
\n\n The mark was awarded for a clear substitution or an answer to at least 3sf. Many gained the mark for a clear substitution with a conversion from g to kg somewhere in their response. Fewer gave the answer to the correct number of sf.\n
\n\n Show that the speed of shuttle S relative to observer P is approximately 0.6\n \n c\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n «−» 0.63\n \n c\n \n ✓\n
\n\n
\n\n \n \n Award [2]\n \n if\n \n MP1\n \n correct and correct answer given to 1 significant figure.\n \n
\n\n the initial rate, in kW, of thermal energy transfer by conduction through the base of the pot.\n
\n\n [1]\n
\n\n 45 × 0.15 × 3.4 × 10\n \n 4\n \n = 230 «kW» ✓\n
\n\n A beaker containing 1 kg of water at room temperature is heated on a 400 W hot plate. The specific heat capacity of water is 4200 J kg\n \n –1\n \n K\n \n –1\n \n .\n
\n\n The temperature of the water increases until it reaches a constant value. It is then removed from the hot plate.\n
\n\n What will be the initial rate of change of temperature?\n
\n\n A. 10 K s\n \n –1\n \n
\n\n B. 1 K s\n \n –1\n \n
\n\n C. 0.1 K s\n \n –1\n \n
\n\n D. 0.01 K s\n \n –1\n \n
\n\n [1]\n
\n\n C\n
\n\n An object moves with simple harmonic motion. The acceleration of the object is\n
\n\n A. constant.\n
\n\n B. always directed away from the centre of the oscillation.\n
\n\n C. a maximum at the centre of the oscillation.\n
\n\n D. a maximum at the extremes of the oscillation.\n
\n\n [1]\n
\n\n D\n
\n\n The design of the pad encloses the resistor in a material that traps air. The design also places the resistor close to the top surface of the pad.\n
\n\n \n
\n Explain, with reference to thermal energy transfer, why the pad is designed in this way.\n
\n\n [3]\n
\n\n Air is a poor «thermal» conductor ✓\n
\n\n Lack of convection due to air not being able to move in material ✓\n
\n\n Appropriate statement about energy transfer between the pet, the resistor and surroundings ✓\n
\n\n The rate of thermal energy transfer to the top surface is greater than the bottom «due to thinner material» ✓\n
\n\n
\n\n \n Accept air is a good insulator\n \n
\n\n Suggest an appropriate measuring instrument for determining\n \n b\n \n .\n
\n\n [1]\n
\n\n instrument (capable of reading to 0.05 mm) with reason related to resolution of instrument ✓\n
\n\n \n eg micrometer screw gauge, Vernier caliper, travelling microscope\n \n
\n\n An object of mass 2.0 kg is on a horizontal surface. The object is pulled by a force of 12.0 N and accelerates at 2.0 m s\n \n −2\n \n .\n
\n\n What is the coefficient of dynamic friction between the object and the surface?\n
\n\n \n
\n
\n A. 0.3\n
\n B. 0.4\n
\n\n C. 0.6\n
\n\n D. 0.8\n
\n\n [1]\n
\n\n B\n
\n\n A group of students perform an experiment to find the refractive index of a glass block. They measure various values of the angle of incidence\n \n i\n \n and angle of refraction\n \n r\n \n for a ray entering the glass from air. They plot a graph of the sin\n \n r\n \n against sin\n \n i\n \n .\n
\n\n \n
\n They determine the gradient of the graph to be\n \n m\n \n .\n
\n\n Which of the following gives the critical angle of the glass?\n
\n\n
\n A. sin\n \n −1\n \n (\n \n m\n \n )\n
\n B. sin\n \n −1\n \n \n
\n\n C.\n \n m\n \n
\n\n D.\n \n
\n\n
\n\n
\n\n A\n
\n\n Outline how a standing wave is produced on the string.\n
\n\n [2]\n
\n\n «travelling» wave moves along the length of the string and reflects «at fixed end»\n \n ✓\n \n
\n\n superposition/interference of incident and reflected waves\n \n ✓\n \n
\n\n the superposition of the reflections is reinforced only for certain wavelengths\n \n ✓\n \n
\n\n A particle performs simple harmonic motion (shm). What is the phase difference between the displacement and the acceleration of the particle?\n
\n\n A. 0\n
\n\n B.\n \n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n
\n\n
\n\n [1]\n
\n\n C\n
\n\n Show that the speed of the wave on the string is about 240 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Answer must be to 3 or more sf\n \n or\n \n working shown for\n \n MP2.\n \n \n
\n\n Determine the ratio\n \n .\n
\n\n [2]\n
\n\n \n =\n \n ✓\n
\n\n = 10.8 ≈ 11 ✓\n
\n\n
\n\n \n Award\n \n MP1\n \n if ratio shown with distance or parallax angle.\n \n
\n\n \n Award\n \n MP1\n \n for any correct substitution into ratio expression\n \n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n \n Allow\n \n ECF\n \n for incorrect distances from\n \n b(i)\n \n or\n \n b(ii)\n \n .\n \n
\n\n Calculate the component of momentum of the first curling stone perpendicular to the initial direction.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Show that the speed of the spacecraft is 0.80\n \n c\n \n as measured in S.\n
\n\n [1]\n
\n\n moves 4 ly in 5 years\n \n \n OR\n \n \n slope of angle with time axis is 0.8 ✓\n
\n\n
\n\n \n Allow evidence for mark on the graph.\n \n
\n\n Calculate the power dissipated in the circuit.\n
\n\n [1]\n
\n\n power\n \n \n ✓\n \n
\n\n Hence, calculate the vertical component of the velocity of ball B after the collision.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n = «−»0.71 «m s\n \n −1\n \n » ✓\n
\n\n Two trolleys of equal mass travel in opposite directions as shown.\n
\n\n \n
\n The trolleys collide head-on and stick together.\n
\n\n What is their velocity after the collision?\n
\n\n A. 1 m s\n \n −1\n \n
\n\n B. 2 m s\n \n −1\n \n
\n\n C. 5 m s\n \n −1\n \n
\n\n D. 10 m s\n \n −1\n \n
\n\n [1]\n
\n\n A\n
\n\n The majority of SL candidates selected option B, finding the difference in velocity but neglecting to recognize that mass will have doubled. This question had a relatively high discrimination index suggesting more able candidates had greater success demonstrating this recognition.\n
\n\n Two containers,\n \n and\n \n , are filled with an ideal gas at the same pressure.\n
\n\n The volume of\n \n is four times the volume of\n \n . The temperature of\n \n is 327 °C and the temperature of\n \n is 27 °C.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Predict whether the collision is elastic.\n
\n\n [4]\n
\n\n Initial kinetic energy\n \n
\n\n Final kinetic energy\n \n ✓\n
\n\n \n ✓\n
\n\n Final energy is less than the initial energy hence inelastic ✓\n
\n\n \n Show that the average force exerted on the ball by the racket is about 50 N.\n \n
\n\n [2]\n
\n\n use of Δ\n \n t =\n \n \n «\n \n (28 – 12) × 10\n \n –3\n \n =\n \n »\n \n 16 × 10\n \n –3\n \n \n «\n \n s\n \n »\n \n ✔\n \n \n
\n\n \n \n \n =«\n \n »\n \n \n \n OR\n \n \n 53 «N» ✔\n \n \n
\n\n \n \n \n NOTE: Accept a time interval from 14 to 16\n \n \n \n \n \n ms\n \n \n \n \n \n
\n Allow ECF from incorrect time interval\n \n \n \n
\n \n one\n \n advantage of energy production by nuclear fusion compared to nuclear fission.\n
\n\n [1]\n
\n\n Plentiful fuel supplies\n \n \n OR\n \n \n larger specific energy\n \n \n OR\n \n \n larger energy density\n \n \n OR\n \n \n little or no «major radioactive» waste products ✓\n
\n\n \n Allow descriptions such as “more energy per unit mass” or “more energy per unit volume”\n \n
\n\n \n A boat with an output engine power of 15 kW moves through water at a speed of 10 m s\n \n -1\n \n . What is the resistive force acting on the boat?\n
\n \n
\n \n A. 0.15 kN\n
\n \n
\n \n B. 0.75 kN\n
\n \n
\n \n C. 1.5 kN\n
\n \n
\n \n D. 150 kN\n \n
\n\n [1]\n
\n\n C\n
\n\n The diagram shows the emission spectrum of an atom.\n
\n\n \n
\n Which of the following atomic energy level models can produce this spectrum?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Deduce the scattering angle for the photon.\n
\n\n [2]\n
\n\n (for this interaction)\n
\n\n \n and therefore\n \n must equal 1 ✓\n
\n\n so cos theta = 0 and theta = 90 deg ✓\n
\n\n What is the escape speed from the surface of a planet of radius\n \n \n \n that has an acceleration of gravity\n \n \n \n at its surface?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Titan has an atmosphere of nitrogen. The albedo of the atmosphere is 0.22. The surface of Titan may be assumed to be a black body. Explain why the\n \n average\n \n intensity of solar radiation\n \n absorbed\n \n by the whole surface of Titan is 3.1 W m\n \n −2\n \n
\n\n [3]\n
\n\n exposed surface is ¼ of the total surface ✓\n
\n\n absorbed intensity = (1−0.22) × incident intensity ✓\n
\n\n 0.78 × 0.25 × 15.7\n \n \n OR\n \n \n 3.07 «W m\n \n −2\n \n » ✓\n
\n\n
\n\n \n Allow 3.06 from rounding and 3.12 if they use 16\n \n W m\n \n −2\n \n .\n
\n\n An electric motor of efficiency 0.75 is connected to a power supply with an emf of 20 V and negligible internal resistance. The power output of the motor is 120 W. What is the average current drawn from the power supply?\n
\n\n
\n\n A. 3.1 A\n
\n\n B. 4.5 A\n
\n\n C. 6.0 A\n
\n\n D. 8.0 A\n
\n\n [1]\n
\n\n D\n
\n\n \n Calculate the average force exerted by the racquet on the ball.\n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n \n \n \n \n \n =\n \n \n \n 148«\n \n \n \n »≈150«\n \n \n \n \n \n » ✔\n \n
\n\n
\n\n At both HL and SL many candidates scored both marks for correctly answering this. A straightforward start to the paper. For those not gaining both marks it was possible to gain some credit for calculating either the change in momentum or the acceleration. At SL some used 64 ms-1 as a value for a and continued to use this value over the next few parts to the question.\n
\n\n When the spheres move outward, the angular speed decreases from 20 rad s\n \n −1\n \n to 12 rad s\n \n −1\n \n . Calculate the percentage change in rotational kinetic energy that occurs when the spheres move outward.\n
\n\n [2]\n
\n\n \n «E\n \n \n k\n \n =»\n \n \n Lω\n \n \n 1\n \n \n =\n \n Lω\n \n 2\n \n \n ✓\n
\n\n \n \n OR\n \n \n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n «\n \n L\n \n is constant so»\n \n E\n \n \n k\n \n is proportional to\n \n ω\n \n ✓\n
\n\n 40 % «energy loss» ✓\n
\n\n
\n\n \n \n MP1\n \n is for understanding that angular momentum is constant so change in rotational kinetic energy is proportional to change in angular velocity\n \n
\n\n \n \n Award [0]\n \n if E = 0.5 I ω\n \n 2\n \n is used with the same I value for both values of E\n \n
\n\n \n Award\n \n [2]\n \n for\n \n BCA\n \n \n
\n\n Show that the wavelength of an electron in the beam is about\n \n .\n
\n\n [1]\n
\n\n \n \n \n \n OR\n \n \n \n ✓\n \n
\n\n \n \n
\n Answer to at least\n \n s.f. (i.e. 3.0)\n \n \n
\n An easy calculation with only one energy conversion to consider and a 'show' answer to help.\n
\n\n Outline how this standing wave pattern of melted spots is formed.\n
\n\n [2]\n
\n\n standing waves form «in the oven» by superposition / constructive interference ✓\n
\n\n energy transfer is greatest at the antinodes «of the standing wave pattern» ✓\n
\n\n Describe\n \n two\n \n ways in which standing waves differ from travelling waves.\n
\n\n [2]\n
\n\n energy is not propagated by standing waves\n \n ✓\n \n
\n\n amplitude constant for travelling waves\n \n \n OR\n \n \n amplitude varies with position for standing waves\n \n \n OR\n \n \n standing waves have nodes/antinodes\n \n ✓\n \n
\n\n phase varies with position for travelling waves\n \n \n OR\n \n \n phase constant inter-node for standing waves\n \n ✓\n \n
\n\n travelling waves can have any wavelength\n \n \n OR\n \n \n standing waves have discrete wavelengths\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n \n Determine the fractional uncertainty in\n \n v\n \n when\n \n T\n \n = 2.115 s, correct to\n \n one\n \n significant figure.\n \n
\n\n [2]\n
\n\n \n \n \n \n AND\n \n \n \n ✔\n \n
\n\n \n \n «\n \n »0.04\n \n ✔\n \n \n \n
\n\n \n \n \n NOTE: Accept 4 %\n \n \n \n
\n\n \n A particle with a charge\n \n ne\n \n is accelerated through a potential difference\n \n V\n \n .\n
\n \n
\n \n What is the magnitude of the work done on the particle?\n \n
\n\n \n \n A.\n \n \n \n
\n \n \n
\n \n \n B.\n \n \n \n
\n \n \n
\n \n \n C.\n \n \n \n
\n \n \n
\n \n \n D.\n \n \n \n \n \n
\n\n [1]\n
\n\n B\n
\n\n Discuss how the results of the experiment provide evidence for matter waves.\n
\n\n [2]\n
\n\n \n «\n \n \n the shape of the graph suggests that\n \n \n »\n \n \n electrons undergo diffraction\n \n \n «\n \n \n with carbon nuclei\n \n \n »\n \n \n ✓\n \n
\n\n \n only waves diffract\n \n \n ✓\n \n
\n\n This question was challenging for candidates many of whom seemed to have little idea of the experiment. Many answers discussed deflection, with the idea that forces between the electron and the nucleus causing it to deflect at a particular angle. This was often combined with the word interference to suggest evidence of matter waves. A number of answers described a demonstration the candidates remembered seeing so answers talked about fuzzy green rings.\n
\n\n A student is verifying the equation\n
\n\n \n \n \n \n \n
\n\n The percentage uncertainties are:\n
\n\n
\n\n \n
\n What is the percentage uncertainty in x?\n
\n\n A. 5 %\n
\n\n B. 15 %\n
\n\n C. 25 %\n
\n\n D. 30 %\n
\n\n [1]\n
\n\n B\n
\n\n This question was well answered by candidates, as shown by a high difficulty index.\n
\n\n Calculate the maximum height risen by the centre of the ball.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n Rebound speed is halved so energy less by a factor of 4 ✓\n
\n Hence height is\n \n =23.8 «cm» ✓\n
\n \n \n ALTERNATIVE 2\n
\n \n \n Use of conservation of energy /\n \n × 0.800 × 2.16\n \n 2\n \n = 0.800 × 9.8 ×\n \n h\n
\n \n OR\n \n \n
\n Use of proper kinematics equation (e.g. 0 = 2.16\n \n 2\n \n − 2 × 9.8 ×\n \n h\n \n ) ✓\n
\n\n \n h\n \n = 23.8 «cm» ✓\n
\n\n \n
\n Allow\n \n ECF\n \n from\n \n b(i)\n \n \n
\n Calculate, in g, the mass of the gas.\n
\n\n [3]\n
\n\n Use of\n \n \n \n OR\n \n \n \n ✓\n
\n\n Mass of gas =\n \n n\n \n ×\n \n N\n \n \n A\n \n × mass of molecule\n
\n \n \n OR\n \n \n
\n Mass of gas = N\n \n \n × mass of molecule ✓\n
\n 5.1 «g» ✓\n
\n\n A charged sphere in a gravitational field is initially stationary between two parallel metal plates. There is a potential difference\n \n V\n \n between the plates.\n
\n\n \n
\n Three changes can be made:\n
\n\n I. Increase the separation of the metal plates\n
\n II. Increase\n \n V\n \n
\n III. Apply a magnetic field into the plane of the paper\n
\n What changes made separately will cause the charged sphere to accelerate?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n A\n
\n\n Option C was a very successful distractor, selected by the majority of candidates. Most candidates missed that change III (\"Apply a magnetic field into the plane of the paper\") can never be correct if the charge is stationary.\n
\n\n Explain, by reference to Faraday’s law of electromagnetic induction, why there is an electromotive force (emf) induced in the loop as it leaves the region of magnetic field.\n
\n\n [2]\n
\n\n The induced emf is equal/proportional/related to the «rate of» change of «magnetic» flux/flux linkage ✓\n
\n\n Flux is changing because the area pierced/enclosed by magnetic field lines changes «decreases»\n
\n\n \n \n OR\n \n \n
\n\n Flux is changing because the loop is leaving/moving out of the «magnetic» field. ✓\n
\n\n \n Need to see a connection between the EMF and change in flux for\n \n MP1\n \n .\n \n
\n\n \n Need to see a connection between the area changing or leaving the field and the change in flux for\n \n MP2\n \n \n
\n\n \n T\n \n is measured with an electronic stopwatch that measures to the nearest 0.1 s.\n
\n\n Describe how an uncertainty in\n \n T\n \n of less than 0.1 s can be achieved using this stopwatch.\n
\n\n [2]\n
\n\n by measuring the time for many bounces ✓\n
\n\n and dividing the result by the number of bounces ✓\n
\n\n Three statements about the binding energy are provided.\n
\n\n I. The binding energy is the energy required to completely separate the nucleons.\n
\n II. The binding energy is equivalent, in units of energy, to the mass defect when a nucleus is formed from its nucleons.\n
\n III. The binding energy is the energy released when a nucleus is formed from its nucleons.\n
\n Which statements are true?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n Calculate the power transferred to the air by the aircraft.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n power\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n Power\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n HL only. It was common to see answers that neglected to average the velocity and consequently arrived at an answer twice the size of the correct one. This was awarded 1 of the 2 marks.\n
\n\n \n The damping of the bridge system can be varied. Draw, on the graph, a second curve when the damping is larger.\n \n
\n\n [2]\n
\n\n \n similar shape with lower amplitude ✔\n
\n \n
\n \n maximum shifted slightly to left of the original curve ✔\n \n
\n\n \n \n \n Amplitude must be lower than the original, but allow the amplitude to be equal at the extremes.\n \n \n \n
\n\n A correct curve, with lower amplitude and shifted left, was drawn by most candidates.\n
\n\n Estimate, using the graph, the maximum height of the bottle.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Attempt to count squares ✓\n
\n\n Area of one square found ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4 m) ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n Uses area equation for either triangle ✓\n
\n\n Correct read offs for estimate of area of triangle ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4) ✓\n
\n\n State and explain the wavelength of the sound measured at M.\n
\n\n [2]\n
\n\n wavelength = 26 cm ✓\n
\n\n
\n peak to peak distance is the path difference which is one wavelength\n
\n \n \n OR\n \n \n
\n\n this is the distance B moves to be back in phase «with A» ✓\n
\n\n
\n\n \n Allow 25 − 27\n \n cm\n \n for\n \n MP1\n \n .\n \n
\n\n Many candidates recognized that the wavelength was 26 cm, but the explanations were lacking the details about what information the graph was actually providing. Examiners were looking for a connection back to path difference, and not simply a description of peak-to-peak distance on the graph. Some candidates did not state a wavelength at all, and instead simply discussed the concept of wavelength or suggested that the wavelength was constant.\n
\n\n Two containers,\n \n and\n \n , are filled with an ideal gas at the same pressure.\n
\n\n The volume of\n \n is four times the volume of\n \n . The temperature of\n \n is 327 °C and the temperature of\n \n is 27 °C.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n An atom of hydrogen (\n \n ) and an atom of helium (\n \n ) are moving with the same kinetic energy.\n
\n\n The de Broglie wavelength of the hydrogen atom is\n \n and the de Broglie wavelength of the helium atom is\n \n .\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n \n The motion of an object is described by the equation\n \n
\n\n \n acceleration ∝ − displacement.\n \n
\n\n \n What is the direction of the acceleration relative to that of the displacement and what is the displacement when the speed is a maximum?\n \n
\n\n \n
\n [1]\n
\n\n D\n
\n\n \n Two power supplies, one of constant emf 24 V and the other of variable emf\n \n P\n \n , are connected to two resistors as shown. Both power supplies have negligible internal resistances.\n \n
\n\n \n \n \n
\n \n \n What is the magnitude of\n \n P\n \n for the reading on the ammeter to be zero?\n \n \n
\n\n \n \n A. Zero\n
\n \n \n
\n \n \n B. 6 V\n
\n \n \n
\n \n \n C. 8 V\n
\n \n \n
\n \n \n D. 18 V\n \n \n
\n\n [1]\n
\n\n B\n
\n\n Monochromatic light is incident on two very narrow slits. The light that passes through the slits is observed on a screen. M is directly opposite the midpoint of the slits.\n \n represents the displacement from M in the direction shown.\n
\n\n \n
\n A student argues that what will be observed on the screen will be a total of two bright spots opposite the slits. Explain why the student’s argument is incorrect.\n
\n\n [2]\n
\n\n light acts as a wave «and not a particle in this situation» ✓\n
\n\n light at slits will diffract / create a diffraction pattern ✓\n
\n\n light passing through slits will interfere / create an interference pattern «creating bright and dark spots» ✓\n
\n\n Calculate, in terms of\n \n g\n \n , the maximum acceleration of P.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n Calculate the period of oscillations of\n \n q\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n .\n \n
\n\n Outline why the magnetic flux in ring B increases.\n
\n\n [1]\n
\n\n ring B cuts an increasing number of magnetic field lines ✓\n
\n\n \n OR\n \n
\n\n magnetic field from current in A increases at the position of B ✓\n
\n\n A body is held in translational equilibrium by three coplanar forces of magnitude\n \n ,\n \n and\n \n . Three statements about these forces are\n
\n\n I. all forces are perpendicular to each other\n
\n II. the forces cannot act in the same direction\n
\n III. the vector sum of the forces is equal to zero.\n
\n Which statements are true?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n C\n
\n\n Determine the fundamental SI unit for\n \n a\n \n .\n
\n\n [2]\n
\n\n kg m s\n \n −2\n \n \n \n OR\n \n \n m\n \n 2\n \n s\n \n −2\n \n seen ✓\n
\n\n kg m\n \n −1\n \n ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n .\n \n
\n\n Students seem to be well prepared for this sort of question, as it was high-scoring.\n
\n\n \n Cylinder X has a volume\n \n \n \n and contains 3.0 mol of an ideal gas. Cylinder Y has a volume\n \n \n \n and contains 2.0 mol of the same gas.\n
\n \n
\n \n The gases in X and Y are at the same temperature\n \n \n \n \n .\n \n The containers are joined by a valve which is opened so that the temperatures do not change.\n \n
\n\n \n What is the change in pressure in X?\n \n
\n\n \n A.\n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n
\n\n [1]\n
\n\n A\n
\n\n After passing through the circular hole the electrons strike a fluorescent screen.\n
\n\n Predict whether an apparatus such as this can demonstrate that moving electrons have wave properties.\n
\n\n [4]\n
\n\n idea that de Broglie wavelength and hole size must be similar ✓\n
\n\n Use of\n \n ✓\n
\n\n Leading to\n \n around 5 x 10\n \n −11\n \n m (which is unrealistic for a practical situation) ✓\n
\n\n It would not be possible to construct this hole\n
\n \n OR\n \n
\n hole must be smaller than an atom so impossible ✓\n
\n Determine the largest magnitude of\n \n F\n \n for which the block and the object do not move relative to each other.\n
\n\n [3]\n
\n\n \n F\n \n = 60\n \n a ✓\n \n
\n\n \n F\n \n \n f\n \n = 0.6 × 15 × 9.8 «= 88.2 N» ✓\n
\n\n \n «N» ✓\n
\n\n
\n\n \n Allow use of a =\n \n 0.6\n \n g leading to 353 N.\n \n
\n\n An electromagnetic wave enters a medium of lower refractive index.\n
\n\n Three statements are made:\n
\n\n I. The wavelength of the wave has increased.\n
\n II. The frequency of the wave has decreased.\n
\n III. The speed of the wave has increased.\n
\n What is true about the properties of the wave?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n Diagram 1 shows the variation with position of the displacement of a standing wave formed on a string.\n
\n\n Diagram 2 shows the variation with position of the displacement of a travelling wave moving to the right along a string.\n
\n\n \n
\n Points P, Q, R and S are points on the string.\n
\n\n What is the phase difference between P and Q and the phase difference between R and S?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n Determine, using the diagram or otherwise, the space coordinate\n \n ′ of event R in S′.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n Using diagram:\n \n
\n\n line from R parallel to prime ct axis until it intersects space axis ✓\n
\n\n use of scale from (b) to estimate coordinate to\n \n ' = (1.3 ± 0.2) ly ✓\n
\n\n \n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n Using Lorentz transformation:\n \n
\n\n event R has coordinates\n \n =\n \n ct\n \n = 4.00 ly in S ✓\n
\n\n so\n \n ' = «\n \n (\n \n −\n \n vt\n \n ) =\n \n × (4.00 − 0.80 × 4.00)» = 1.33 ly ✓\n
\n\n show that the speed of the ball is about 4.3 m s\n \n −1\n \n .\n
\n\n [1]\n
\n\n \n v\n \n =\n \n \n \n OR\n \n \n = 4.32 «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Must see either full substitution or answer to at least 3 s.f.\n \n
\n\n Estimate the fraction of tritium remaining after one year.\n
\n\n [2]\n
\n\n \n = «\n \n »0.056«y\n \n −1\n \n »\n \n \n OR\n \n \n \n \n \n OR\n \n \n \n
\n\n 0.945\n \n \n OR\n \n \n 94.5% ✓\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n Outline how a standing wave is produced on the string.\n
\n\n [2]\n
\n\n «travelling» wave moves along the length of the string and reflects «at fixed end»\n \n ✓\n \n
\n\n superposition/interference of incident and reflected waves\n \n ✓\n \n
\n\n the superposition of the reflections is reinforced only for certain wavelengths\n \n ✓\n \n
\n\n Outline why it is unlikely that the relationship between\n \n T\n \n and\n \n V\n \n is linear.\n
\n\n [1]\n
\n\n it is not possible to draw a straight line through all the error bars ✓\n
\n\n \n Calculate the temperature at A if the temperature at B is\n \n −\n \n 40°C.\n \n
\n\n [1]\n
\n\n \n \n T\n \n \n A\n \n = 816\n \n «\n \n \n K\n \n \n »\n \n \n \n OR\n \n \n 543«\n \n °C\n \n »\n \n \n \n ✔\n \n \n
\n\n The temperature at A was found correctly by most candidates.\n
\n\n State the range of current that the ammeter can measure as the slider S of the potential divider is moved from Q to P.\n
\n\n [1]\n
\n\n \n from\n \n to\n \n \n \n ✓\n \n
\n\n Surprisingly a significant number of candidates had difficulty with this. Answers of 20 mA and 4 V were often seen.\n
\n\n Determine the terminal velocity of the sphere.\n
\n\n [3]\n
\n\n radius of sphere\n \n ✓\n
\n\n
\n\n weight of sphere\n \n
\n\n \n \n OR\n \n \n
\n\n \n ✓\n
\n\n
\n\n \n ✓\n
\n\n
\n\n \n \n Accept use of\n \n leading to\n \n \n \n
\n\n \n \n Allow implicit calculation of radius for MP1\n \n \n
\n\n \n \n Do not allow ECF for MP3 if buoyant force omitted.\n \n \n
\n\n Only those candidates who forgot to include the buoyant force missed marks here.\n
\n\n Explain why intensity maxima are observed at X and Y.\n
\n\n [2]\n
\n\n two waves superpose/mention of superposition/mention of «constructive» interference ✔\n
\n\n they arrive in phase/there is a path length difference of an integer number of wavelengths ✔\n
\n\n \n Ignore references to nodes/antinodes\n \n .\n
\n\n Many candidates were able to discuss the interference that is taking place in this question, but few were able to fully describe the path length difference. That said, the quality of responses on this type of question seems to have improved over the last few examination sessions with very few candidates simply discussing the crests and troughs of waves.\n
\n\n The vertical acceleration of the load downwards is 2.4 m s\n \n −2\n \n .\n
\n\n Calculate the tension in the string.\n
\n\n [2]\n
\n\n use of\n \n ma = mg − T\n \n «3.5 x 2.4 = 3.5\n \n g − T\n \n »\n
\n\n \n \n OR\n \n \n
\n\n \n T\n \n = 3.5(\n \n g −\n \n 2.4) ✓\n
\n\n 26 «N» ✓\n
\n\n
\n\n \n Accept 27 N from g = 10 m s\n \n −2\n \n \n
\n\n Some students simply calculated the net force acting on the load and did not recognize that this was not the tension force. Many set up a net force equation but had the direction of the forces backwards. This generally resulted from sloppy problem solving.\n
\n\n Two nuclides present in spent nuclear fuel\n \n are and cerium-144 (\n \n ). The initial activity of a sample of pure\n \n is about 40 times greater than the activity of the same amount of pure\n \n .\n
\n\n Discuss which of the two nuclides is more likely to require long-term storage once removed from the reactor.\n
\n\n [3]\n
\n\n «For the same number of nuclei,» the activity is inversely related to half-life ✓\n
\n\n Thus\n \n has a longer half-life and will likely require longer storage ✓\n
\n\n Half-lives of their decay products need also be considered when planning storage ✓\n
\n\n In the circuits shown, the cells have the same emf and zero internal resistance. All resistors are identical.\n
\n\n \n
\n What is the order of increasing power dissipated in each circuit?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n \n Show that the total energy of the planet is given by the equation shown.\n \n
\n\n \n \n \n \n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n comparison with\n \n \n \n \n ✔\n \n \n
\n\n \n «to give answer»\n \n
\n\n
\n\n This was generally well answered but with candidates sometimes getting in to trouble over negative signs but otherwise producing well-presented answers.\n
\n\n Estimate the acceleration of the bottle when it is at its maximum height.\n
\n\n [2]\n
\n\n Attempt to calculate gradient of line at\n \n t\n \n = 1.2 s ✓\n
\n\n «−» 9.8 «m s\n \n −2\n \n » (accept 9.6 − 10.0) ✓\n
\n\n \n Gamma (\n \n \n \n ) radiation\n \n
\n\n \n A. is deflected by a magnetic field.\n
\n \n
\n \n B. affects a photographic plate.\n
\n \n
\n \n C. originates in the electron cloud outside a nucleus.\n
\n \n
\n \n D. is deflected by an electric field.\n \n
\n\n [1]\n
\n\n B\n
\n\n Show that the gravitational potential due to the planet and the star at the surface of the planet is about −5 × 10\n \n 9\n \n J kg\n \n −1\n \n .\n
\n\n [3]\n
\n\n \n V\n \n \n planet\n \n = «−»\n \n «−» 5.9 × 10\n \n 7\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n V\n \n \n star\n \n = «−»\n \n «−» 4.9 × 10\n \n 9\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n V\n \n \n planet\n \n +\n \n V\n \n \n star\n \n = «−» 4.9 «09» × 10\n \n 9\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n
\n \n \n Must see substitutions and not just equations.\n \n
\n Outline how an approximate adiabatic change can be achieved.\n
\n\n [2]\n
\n\n \n adiabatic means no transfer of heat in or out of the system\n \n \n ✓\n \n
\n\n \n should be fast\n \n \n ✓\n \n
\n\n \n «can be slow if» the system is insulated\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n A block of glass of mass 5 kg and temperature 30°C is brought into contact with a block of asphalt of mass 20 kg and temperature 75°C. The specific heat capacity of asphalt is twice that of glass. No energy is transferred to the surroundings. What is the final temperature of both blocks?\n
\n\n
\n A. 35°C\n
\n B. 45°C\n
\n\n C. 60°C\n
\n\n D. 70°C\n
\n\n [1]\n
\n\n D\n
\n\n A challenging question, with incorrect alternatives B and C both picked more often than the correct D. By combining the effect of mass and specific heat capacity of both materials, the change of temperature of the glass block is 8× greater than that of the asphalt. Therefore, the difference between the initial temperatures has to be divided into 9 equal parts and the final temperature is one such part below the initial temperature of the asphalt.\n
\n\n Calculate the theoretical equilibrium temperature of the mixture.\n
\n\n [3]\n
\n\n \n
\n\n \n
\n\n One heat capacity term correctly substituted ✓\n
\n\n latent heat correctly substituted\n \n ✓\n
\n\n \n «°C» ✓\n
\n\n Show that the equilibrium surface temperature of Titan is about 90 K.\n
\n\n [1]\n
\n\n \n σT\n \n \n 4\n \n = 3.07\n
\n\n \n \n OR\n \n \n
\n\n \n T\n \n = 86 «K» ✓\n
\n\n A current in a wire lies between the poles of a magnet. What is the direction of the electromagnetic force on the wire?\n
\n\n \n
\n
\n\n [1]\n
\n\n A\n
\n\n Many chose option C, the opposite of the correct response. As always in electromagnetism questions, students need to consider carefully which hand and which fingers to use. We do tend to say that there is little that needs to be memorised in physics, this is probably one of them.\n
\n\n The radius of a circle is measured to be (10.0 ± 0.5) cm. What is the area of the circle?\n
\n\n A. (314.2 ± 0.3) cm\n \n 2\n \n
\n\n B. (314 ± 1) cm\n \n 2\n \n
\n\n C. (314 ± 15) cm\n \n 2\n \n
\n\n D. (314 ± 31) cm\n \n 2\n \n
\n\n [1]\n
\n\n D\n
\n\n This question discriminated well at both HL and SL with many candidates choosing the correct option D. However, option B was also a popular choice particularly at SL. Candidates need to be aware that when performing a calculation e.g. the area as here, the uncertainty also has to be propagated - so a 5% uncertainty in the radius becomes a 10% uncertainty in the area. There were some comments on the G2s that the uncertainty should only have been given to 1sf but this is not always correct as uncertainties are given to the precision of the value, depending on the percentage calculated in the propagation.\n
\n\n Two isolated point masses, P of mass\n \n m\n \n and Q of mass 2\n \n m\n \n , are separated by a distance 3\n \n d\n \n . X is a point a distance\n \n d\n \n from P and 2\n \n d\n \n from Q.\n
\n\n \n
\n What is the net gravitational field strength at X and the net gravitational potential at X?\n
\n\n
\n| \n | \n\n \n Net gravitational field\n \n \n strength at X\n \n | \n\n \n Net gravitational\n \n potential at X\n \n | \n
| \n A.\n | \n\n \n | \n\n 0\n | \n
| \n B.\n | \n\n \n | \n\n \n | \n
| \n C.\n | \n\n \n | \n\n 0\n | \n
| \n D.\n | \n\n \n | \n\n \n | \n
\n
\n\n [1]\n
\n\n D\n
\n\n Which is a vector quantity?\n
\n\n A. Acceleration\n
\n\n B. Energy\n
\n\n C. Pressure\n
\n\n D. Speed\n
\n\n [1]\n
\n\n A\n
\n\n Show that\n \n for the planets in a solar system where\n \n \n \n is the orbital period of a planet and\n \n \n \n is the radius of circular orbit of planet about its sun.\n
\n\n [2]\n
\n\n Equates centripetal force (with Newton’s law gravitation\n \n )\n
\n\n AND\n
\n\n \n ✓\n
\n\n leads to\n \n hence result ✓\n
\n\n A proton and an alpha particle are accelerated by the same electric potential difference. The kinetic energy of the proton is\n \n E\n \n and its de Broglie wavelength is\n \n λ\n \n . What is the kinetic energy and the de Broglie wavelength of the alpha particle?\n
\n\n
\n| \n | \n\n \n Kinetic energy of alpha particle\n \n | \n\n \n De Broglie wavelength of alpha particle\n \n | \n
| \n A.\n | \n\n \n E\n \n | \n\n less than\n \n λ\n \n | \n
| \n B.\n | \n\n \n E\n \n | \n\n greater than\n \n λ\n \n | \n
| \n C.\n | \n\n greater than\n \n E\n \n | \n\n less than\n \n λ\n \n | \n
| \n D.\n | \n\n greater than\n \n E\n \n | \n\n greater than\n \n λ\n \n | \n
\n [1]\n
\n\n C\n
\n\n \n Calculate the ratio\n \n \n \n .\n \n
\n\n [1]\n
\n\n «\n \n \n \n \n ✔\n \n
\n\n This was well answered with the most common mistake being to use the volume of a single atom rather than the total volume of the atoms.\n
\n\n Two identical sources oscillate in phase and produce constructive interference at a point P. The intensity recorded at P is\n \n I\n \n .\n
\n\n What is the intensity at P from one source?\n
\n\n
\n A.\n \n \n I\n \n
\n B.\n \n I\n \n
\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The graph shows the actual variation with displacement\n \n from M of the intensity of the light on the screen.\n \n is the intensity of light at the screen from one slit only.\n
\n\n \n
\n The slits are separated by a distance of 0.18 mm and the distance to the screen is 2.2 m. Determine, in m, the wavelength of light.\n
\n\n [2]\n
\n\n Ue of\n \n s\n \n =\n \n =\n \n \n \n OR\n \n \n \n s\n \n =\n \n =\n \n ✓\n
\n\n \n = «\n \n =» 4.6 × 10\n \n −7\n \n «m» ✓\n
\n\n Two ideally lagged bars have the same length and are made from the same metal. The diameters of the bars are different. One end of each bar is held at 100 °C and the other end is held at 0 °C.\n
\n\n For each bar\n
\n\n
\n A. the rate of energy transfer is the same\n
\n B. the temperature gradient is the same\n
\n\n C. the temperature gradient is non-linear\n
\n\n D. the temperature gradient\n \n
\n\n [1]\n
\n\n B\n
\n\n Calculate the theoretical equilibrium temperature of the mixture.\n
\n\n [3]\n
\n\n \n
\n\n \n
\n\n One heat capacity term correctly substituted ✓\n
\n\n latent heat correctly substituted\n \n ✓\n
\n\n \n «°C» ✓\n
\n\n Determine the time coordinate\n \n ct′\n \n when the flash of light reaches the spaceship, according to an observer at rest in the spaceship.\n
\n\n [2]\n
\n\n (\n \n ct\n \n ')\n \n 2\n \n − 0 = 5\n \n 2\n \n − 3\n \n 2\n \n
\n\n \n \n OR\n \n \n
\n\n \n = 1.25 ✓\n
\n\n
\n\n \n ct\n \n ' = 4 «km»\n
\n\n \n \n OR\n \n \n
\n\n \n t\n \n ' = 13 «\n \n µ\n \n s» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (b)\n \n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n The force per unit length between two long parallel current-carrying wires is\n \n F\n \n .\n
\n\n The distance between the wires is halved and the current in each wire is doubled. What is the force per unit length of the wires after the change?\n
\n\n
\n A.\n \n F\n \n
\n B. 2\n \n F\n \n
\n\n C. 4\n \n F\n \n
\n\n D. 8\n \n F\n \n
\n\n [1]\n
\n\n D\n
\n\n Calculate the pressure of the gas in the container.\n
\n\n [1]\n
\n\n \n seen\n \n ✓\n
\n\n \n Calculate the binding energy per nucleon for uranium-238.\n \n
\n\n [3]\n
\n\n \n 234 × 7.6\n \n \n OR\n \n \n 4 × 7.07 ✔\n \n
\n\n \n BE\n \n \n U\n \n =\n \n \n « 234\n \n ×\n \n 7.6\n \n + 4 × 7.07 – 4.27 =\n \n »\n \n « MeV » ✔\n \n \n
\n\n \n \n \n \n « MeV » ✔\n \n \n \n
\n\n \n \n \n \n \n NOTE: Allow ECF from MP2\n
\n Award\n \n [3]\n \n for bald correct answer\n
\n Allow conversion to J, final answer is 1.2\n \n ×\n \n 10\n \n –12\n \n \n \n \n \n \n
\n Calculate the power transferred to the air by the aircraft.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n power\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n Power\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n HL only. It was common to see answers that neglected to average the velocity and consequently arrived at an answer twice the size of the correct one. This was awarded 1 of the 2 marks.\n
\n\n \n A circular coil of wire moves through a region of uniform magnetic field directed out of the page.\n \n
\n\n \n \n \n
\n \n \n What is the direction of the induced conventional current in the coil for the marked positions?\n \n \n
\n\n \n \n \n \n \n
\n [1]\n
\n\n C\n
\n\n A thermodynamic cycle consisting of an adiabatic, isovolumetric and isothermal processes is shown.\n
\n\n \n
\n Which of the following correctly identifies the processes of the cycle?\n
\n\n
\n| \n | \n\n \n Adiabatic\n \n | \n\n \n Isovolumetric\n \n | \n\n \n Isothermal\n \n | \n
| \n A.\n | \n\n X→Y\n | \n\n Y→Z\n | \n\n Z→X\n | \n
| \n B.\n | \n\n Z→X\n | \n\n X→Y\n | \n\n Y→Z\n | \n
| \n C.\n | \n\n Z→X\n | \n\n Y→Z\n | \n\n X→Y\n | \n
| \n D.\n | \n\n Y→Z\n | \n\n Z→X\n | \n\n X→Y\n | \n
\n [1]\n
\n\n C\n
\n\n A negatively charged particle is stationary halfway between two horizontal charged plates. The plates are separated by a distance\n \n d\n \n with potential difference\n \n V\n \n between them.\n
\n\n \n
\n What is the magnitude of the electric field and direction of the electric field at the position of the particle?\n
\n\n
\n| \n | \n\n \n Magnitude of\n \n \n \n electric field\n \n | \n \n \n Direction of\n \n \n \n electric field\n \n | \n
| \n A.\n | \n\n \n | \n\n up\n | \n
| \n B.\n | \n\n \n | \n\n up\n | \n
| \n C.\n | \n\n \n | \n\n down\n | \n
| \n D.\n | \n\n \n | \n\n down\n | \n
\n [1]\n
\n\n D\n
\n\n Show that the kinetic energy of the satellite in orbit is about 2 × 10\n \n 10\n \n J.\n
\n\n [2]\n
\n\n orbital radius\n \n «\n \n m» ✓\n
\n\n \n \n \n OR\n \n \n \n «J» ✓\n
\n\n
\n\n \n Award\n \n [1] max\n \n for answers ignoring orbital height (KE = 2.5 × 10\n \n \n \n 10\n \n \n J\n \n ).\n \n
\n\n This question was well done, with only a few missing the height of the satellite.\n
\n\n Discuss how the motion of the molecules of a gas gives rise to pressure in the gas.\n
\n\n [3]\n
\n\n The momentum of a molecule changes when it collides with a container wall ✓\n
\n\n From\n \n and Newton’s third law, this leads to a force exerted on the wall by the molecule ✓\n
\n\n The average force exerted by all the molecules on a unit area of the wall is equivalent to pressure ✓\n
\n\n
\n\n A satellite of mass\n \n orbits a planet of mass\n \n in a circular orbit of radius\n \n . What is the work that must be done on the satellite to increase its orbital radius to\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Source S produces sound waves of speed\n \n v\n \n and frequency\n \n . S moves with constant velocity\n \n away from a stationary observer.\n
\n\n \n
\n What is the frequency measured by the observer?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Suggest an appropriate measuring instrument for determining\n \n b\n \n .\n
\n\n [1]\n
\n\n instrument (capable of reading to 0.05 mm) with reason related to resolution of instrument ✓\n
\n\n \n eg micrometer screw gauge, Vernier caliper, travelling microscope\n \n
\n\n A rectangular sheet of paper has dimensions of (30.0 ± 0.5) cm and (20.0 ± 0.5) cm.\n
\n\n What is the percentage uncertainty of the perimeter of the paper?\n
\n\n
\n A. 1 %\n
\n B. 2 %\n
\n\n C. 2.5 %\n
\n\n D. 4 %\n
\n\n [1]\n
\n\n B\n
\n\n The variation of\n \n d\n \n with\n \n W\n \n is shown.\n
\n\n \n
\n Outline\n \n one\n \n experimental reason why the graph does not go through the origin.\n
\n\n [1]\n
\n\n beam bends under its own weight / weight of pan\n
\n\n \n \n OR\n \n \n
\n\n specified systematic error in\n \n d\n \n ✓\n
\n\n The diagram shows two cylindrical wires, X and Y. Wire X has a length\n \n \n \n , a diameter\n \n \n \n , and a resistivity\n \n . Wire Y has a length\n \n , a diameter of\n \n and a resistivity of\n \n .\n
\n\n \n
\n What is\n \n ?\n
\n\n A. 4\n
\n\n B. 2\n
\n\n C. 0.5\n
\n\n D. 0.25\n
\n\n [1]\n
\n\n D\n
\n\n Explain how the difference in part (b)(ii) arises.\n
\n\n [1]\n
\n\n Another particle/«anti» neutrino is emitted «that accounts for this mass / energy» ✓\n
\n\n Calculate the electric potential difference between points A and B.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n Most didn't realise that the key to the answer is the definition of potential or potential difference and tried to answer using one of the formulae in the data booklet, but incorrectly.\n
\n\n \n Draw a graph to show the variation with\n \n t\n \n of the horizontal speed\n \n v\n \n of the ball while it was in contact with the racket. Numbers are\n \n not\n \n required on the axes.\n \n
\n\n \n
\n [2]\n
\n\n \n
\n \n graph must show increasing speed from an initial of zero all the time ✔\n
\n overall correct curvature ✔\n \n
\n Determine the resistance of the variable resistor.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n voltage across X\n \n ✓\n \n
\n\n \n voltage across R\n \n ✓\n \n
\n\n \n resistance of variable resistor\n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n overall resistance\n \n ✓\n
\n\n resistance of X\n \n ✓\n
\n\n resistance of variable resistor\n \n ✓\n
\n\n \n A neutron collides head-on with a stationary atom in the moderator of a nuclear power station. The kinetic energy of the neutron changes as a result. There is also a change in the probability that this neutron can cause nuclear fission.\n
\n \n
\n \n What are these changes?\n \n
\n\n \n \n \n
\n [1]\n
\n\n B\n
\n\n State what is meant by an isolated system.\n
\n\n [1]\n
\n\n Neither mass nor energy is exchanged with the surroundings ✓\n
\n\n \n The percentage uncertainty for\n \n \n \n \n \n is\n \n . State\n \n \n \n \n \n , with its absolute uncertainty.\n \n
\n\n [2]\n
\n\n \n «\n \n of\n \n » =\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n «\n \n of\n \n » =\n \n \n \n ✓\n
\n \n
\n \n rounds uncertainty to 1sf\n
\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n \n \n \n ✓\n \n
\n
\n\n \n \n Allow ECF from (b)(i)\n
\n Award\n \n \n \n [2]\n \n \n \n marks for a bald correct answer\n \n \n
\n Well answered. A significant number did not round the uncertainty to match the value of gamma.\n
\n\n Calculate the current in wire Q.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «A» ✓\n
\n\n Draw, on the axes, the graph to show how the kinetic energy of the cylinder varies with time during\n \n one\n \n period of oscillation\n \n .\n
\n\n \n
\n [2]\n
\n\n \n energy never negative\n \n \n ✓\n \n
\n\n \n correct shape with two maxima\n \n \n ✓\n \n
\n\n \n
\n Most candidates answered with a graph that was only positive so scored the first mark.\n
\n\n Describe the energy change that takes place for\n \n t\n \n > 3.0 s.\n
\n\n [1]\n
\n\n «gravitational» potential energy «of the raindrop» into thermal/internal energy «of the air» ✓\n
\n\n
\n\n \n Accept heat for thermal energy.\n \n
\n\n \n Accept into kinetic energy of air particles.\n \n
\n\n \n Ignore sound energy.\n \n
\n\n Of the wrong answers, the most common ones were gravitational potential to kinetic or the idea that because there was no change in velocity there was no energy transfer. A significant number, though, scored by identifying the change into thermal (most of them), kinetic of air particles (a few answers) or internal (very few).\n
\n\n Experiments with many nuclides suggest that the radius of a nucleus is proportional to\n \n , where\n \n is the number of nucleons in the nucleus. Show that the density of a nucleus remains approximately the same for all nuclei.\n
\n\n [2]\n
\n\n \n volume of a nucleus proportional to\n \n \n \n \n \n AND\n \n \n \n \n mass proportional to\n \n \n \n ✓\n \n
\n\n \n the ratio\n \n independent of\n \n \n \n «\n \n \n hence density the same for all nuclei\n \n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n Both needed for MP1\n \n \n
\n\n This question proved challenging and it wasn't common to find answers that scored both marks. Of those that had the right approach some missed out on both marks by describing A as the mass of the nucleus rather than proportional to the mass of the nucleus.\n
\n\n Explain, by reference to Faraday’s law of electromagnetic induction, why there is an electromotive force (emf) induced in the loop as it leaves the region of magnetic field.\n
\n\n [2]\n
\n\n The induced emf is equal/proportional/related to the «rate of» change of «magnetic» flux/flux linkage ✓\n
\n\n Flux is changing because the area pierced/enclosed by magnetic field lines changes «decreases»\n
\n\n \n \n OR\n \n \n
\n\n Flux is changing because the loop is leaving/moving out of the «magnetic» field. ✓\n
\n\n \n Need to see a connection between the EMF and change in flux for\n \n MP1\n \n .\n \n
\n\n \n Need to see a connection between the area changing or leaving the field and the change in flux for\n \n MP2\n \n \n
\n\n \n Suggest a mechanism by which the additional intensity can be lost.\n \n
\n\n [1]\n
\n\n \n conduction to the air above\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «mainly» evaporation\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n melting ice at the poles\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n reflection of sunlight off the surface of the ocean ✔\n \n
\n\n \n \n \n Do not accept convection or radiation.\n \n \n \n
\n\n Many candidates didn’t understand this question and thought that the answer needed to be some form of human activity that would reduce global temperature rise.\n
\n\n Calculate the percentage uncertainty in the value of\n \n A\n \n .\n
\n\n [2]\n
\n\n attempt to calculate fractional uncertainty in either\n \n a\n \n or\n \n b\n \n [0.0357, 0.0167] ✓\n
\n\n 0.0357 + 0.0167 = 0.05 = 5% ✓\n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n \n V\n \n is provided by two identical power supplies connected in series. The potential difference of each of the power supplies is known with an uncertainty of 0.01 kV.\n
\n\n State the uncertainty in the potential difference\n \n V\n \n .\n
\n\n [1]\n
\n\n 0.02 «kV» ✓\n
\n\n The centre of the Earth and the Moon are a distance\n \n apart. There is a point X between them where their gravitational fields cancel out. The distance from the centre of the Earth to X is\n \n . The mass of the Earth is\n \n and the mass of the Moon is\n \n .\n
\n\n \n
\n What is correct at X?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n In a simple climate model for a planet, the incoming intensity is 400 W m\n \n −2\n \n and the radiated intensity is 300 W m\n \n −2\n \n .\n
\n\n \n
\n The temperature of the planet is constant. What are the reflected intensity from the planet and the albedo of the planet?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n The work done to move a particle of charge 0.25 μC from one point in an electric field to another is 4.5 μJ. Calculate the magnitude of the potential difference between the two points.\n
\n\n [1]\n
\n\n «\n \n » 18 «V» ✓\n
\n\n Identify with ticks [✓] in the table, the forces that can act on electrons and the forces that can act on quarks.\n
\n\n \n
\n [2]\n
\n\n Weak nuclear: 2 ticks ✓\n
\n Strong nuclear: quarks only ✓\n
\n The internal energy of a real gas is\n
\n\n
\n A. zero.\n
\n B. equal to the intermolecular potential energy of the particles.\n
\n\n C. equal to the total kinetic energy of the particles.\n
\n\n D. equal to the sum of the intermolecular potential energy and the total kinetic energy of the particles.\n
\n\n [1]\n
\n\n D\n
\n\n An object oscillates at the free end of a vertical spring. The graph shows the variation of the object’s position with time.\n
\n\n At which position does the object have zero velocity and a negative acceleration?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n The mass of a nucleus of iron-56 (\n \n ) is\n \n M\n \n .\n
\n\n What is the mass defect of the nucleus of iron-56?\n
\n\n
\n\n A.\n \n M\n \n − 26\n \n m\n \n \n p\n \n − 56\n \n m\n \n \n n\n \n
\n\n B. 26\n \n m\n \n \n p\n \n + 30\n \n m\n \n \n n\n \n −\n \n M\n \n
\n\n C. M − 26\n \n m\n \n \n p\n \n − 56\n \n m\n \n \n n\n \n − 26\n \n m\n \n \n e\n \n
\n\n D. 26\n \n m\n \n \n p\n \n + 30\n \n m\n \n \n n\n \n + 26\n \n m\n \n \n e\n \n −\n \n M\n \n
\n\n [1]\n
\n\n B\n
\n\n Outline why the angular speed\n \n ω\n \n decreases when the spheres move outward.\n
\n\n [2]\n
\n\n moment of inertia increases ✓\n
\n\n Angular momentum is conserved ✓\n
\n\n \n
\n Allow algebraic expressions e.g. ω =\n \n so ω decreases for\n \n MP2\n \n \n
\n Calculate the theoretical equilibrium temperature of the mixture.\n
\n\n [3]\n
\n\n \n
\n\n \n
\n\n One heat capacity term correctly substituted ✓\n
\n\n latent heat correctly substituted\n \n ✓\n
\n\n \n «°C» ✓\n
\n\n An object of mass\n \n is falling vertically through the air. The drag force acting on the object is\n \n . What is the best estimate of the acceleration of the object?\n
\n\n A. Zero\n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Outline why repeated measurements of\n \n would not reduce any systematic error in\n \n .\n
\n\n [1]\n
\n\n \n systematic errors «usually» constant/always present/ not influenced by repetition\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Usually very well answered acknowledging that systematic errors are constant and present throughout all measurements.\n
\n\n Theory predicts that\n
\n\n \n
\n\n where\n \n \n \n and\n \n are constants. The fundamental units of\n \n are m\n \n 4\n \n and those of\n \n E\n \n are kg m\n \n −1\n \n s\n \n −2\n \n .\n
\n\n Calculate\n \n and\n \n .\n
\n\n [2]\n
\n\n units of\n \n \n \n : kg m s\n \n −2\n \n ✓\n
\n\n work leading to\n \n and\n \n ✓\n
\n\n State what is meant by an ideal voltmeter.\n
\n\n [1]\n
\n\n infinite resistance\n
\n\n \n \n OR\n \n \n
\n\n no current is flowing through it ✓\n
\n\n A majority of candidates scored a mark by simply stating infinite resistance. Several answers went the other way round, stating a resistance of zero.\n
\n\n Outline the role of the heat exchanger in a nuclear power station.\n
\n\n [1]\n
\n\n Collects thermal energy from the coolant and delivers it to the gas ✓\n
\n\n Prevents the «irradiated» coolant from leaving the reactor vessel ✓\n
\n\n The block falls a distance 0.50 m after its release before hitting the ground. Show that the block hits the ground 0.55 s after release.\n
\n\n [2]\n
\n\n \n a\n \n = 3.27 «ms\n \n −2\n \n » /\n \n a\n \n =\n \n g\n \n /3 ✔\n
\n\n \n \n \n \n \n ✔\n
\n\n = 0.55 «s»\n
\n\n \n Do not apply ECF from MP1 to MP2 if for a=g, giving answer 0.32 s\n \n .\n
\n\n The application of the uniformly accelerated motion to this context was mastered successfully by better candidates.\n
\n\n The dashed line represents the variation with incident electromagnetic frequency\n \n \n \n of the kinetic energy\n \n E\n \n \n K\n \n of the photoelectrons ejected from a metal surface. The metal surface is then replaced with one that requires less energy to remove an electron from the surface.\n
\n\n Which graph of the variation of\n \n E\n \n \n K\n \n with\n \n \n \n will be observed?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n A power station generates\n \n of power at a potential difference of\n \n . The energy is transmitted through cables of total resistance\n \n .\n
\n\n What is the power loss in the cables?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Window 1 is made of a single glass pane of thickness\n \n d\n \n . Window 2 is made of two glass panes of thickness\n \n d\n \n each, separated by a thin air space. Both windows have the same surface area and separate air masses of the same temperature difference.\n
\n\n Thermal energy transferred in unit time through window 1 is\n \n \n \n . The thermal energy transferred in unit time through window 2 is\n
\n\n
\n A. less than\n \n
\n B. equal to\n \n
\n\n C. between\n \n and\n \n \n \n
\n\n D. equal to\n \n
\n\n [1]\n
\n\n A\n
\n\n State and explain one modification that the student can make to reduce the fractional uncertainty for the change in temperature of the metal cube.\n
\n\n [1]\n
\n\n smaller mass of cube\n \n \n OR\n \n \n hotter cube\n \n \n OR\n \n \n more mass of water\n \n \n OR\n \n \n colder water\n \n \n OR\n \n \n more precise thermometer ✓\n
\n\n
\n\n \n Accept reference to repeating the experiment and taking mean values.\n \n
\n\n \n Accept any reasonable answer that increases change in temperature of the cube.\n \n
\n\n \n Do\n \n not\n \n accept more accurate thermometer\n \n
\n\n In the Bohr model for hydrogen, the radius of the electron orbit in the n = 2 state is four times that of the radius in the n = 1 state.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 2\n
\n\n D. 4\n
\n\n [1]\n
\n\n B\n
\n\n A particle undergoes simple harmonic motion of period\n \n . At time\n \n the particle is at its equilibrium position.\n
\n\n What is\n \n when the particle is at its greatest distance from the equilibrium position?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n A stone is thrown vertically up from the top of a cliff with a velocity\n \n v\n \n at time\n \n t\n \n = 0. Air resistance is negligible.\n
\n\n \n
\n What is the variation with time of the velocity of the stone until it hits the ground?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n Two surfaces X and Y emit radiation of the same surface intensity. X emits a radiation of peak wavelength twice that of Y.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 2\n
\n\n D. 16\n
\n\n [1]\n
\n\n D\n
\n\n No unbalanced external forces act on the system of the curling stones. Outline why the momentum of the system does not change during the collision.\n
\n\n [1]\n
\n\n From\n \n , zero net force on the system implies that\n \n
\n\n \n OR\n \n
\n\n From Newton’s third law, the impulse delivered to A is equal but opposite to the impulse delivered to B, hence\n \n for the system ✓\n
\n\n \n Calculate the ratio\n \n \n \n .\n \n
\n\n [1]\n
\n\n «\n \n \n \n \n ✔\n \n
\n\n This was well answered with the most common mistake being to use the volume of a single atom rather than the total volume of the atoms.\n
\n\n The side of the rod can be unlagged or ideally lagged. Explain the difference in energy transfer for these two cases.\n
\n\n [3]\n
\n\n When ideally lagged, no energy transfer can occur through the sides of the bar. ✓\n
\n\n All the power input/ energy input per second at one end will emerge at the other end. ✓\n
\n\n When unlagged, energy transfer occurs from the sides of the bar and the power /energy input per second at input > the energy output per second at the other end. ✓\n
\n\n
\n\n \n Max 1 if answer does not refer to rate of energy transfer in MP2 and MP3.\n \n
\n\n A negatively charged sphere is falling through a magnetic field.\n
\n\n \n
\n What is the direction of the magnetic force acting on the sphere?\n
\n\n
\n A. To the left of the page\n
\n B. To the right of the page\n
\n\n C. Out of the page\n
\n\n D. Into the page\n
\n\n [1]\n
\n\n D\n
\n\n Light from a monochromatic source is incident on a single slit and the resulting diffraction pattern is viewed on a screen. The graph shows the variation of intensity with distance on the screen.\n
\n\n \n
\n The intensity of the source remains the same. The width of the slit is increased.\n
\n\n Which graph correctly shows the variation of intensity after the change? The original curve is shown with a dashed line.\n
\n
\n
\n \n
\n [1]\n
\n\n D\n
\n\n \n Explain how the student could use this apparatus to obtain a more reliable value for λ.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1:\n \n \n
\n \n
\n \n measure the combined width for several fringes\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n repeat measurements ✓\n
\n \n
\n \n take the average\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n so the «percentage» uncertainties are reduced ✓\n
\n \n
\n \n \n \n ALTERNATIVE 2:\n \n \n
\n \n
\n \n increase\n \n D\n \n «hence\n \n s\n \n »\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n Decrease\n \n d\n \n ✓\n
\n \n
\n \n so the «percentage» uncertainties are reduced ✓\n \n
\n\n \n \n \n Do not accept answers which suggest using different apparatus.\n \n \n \n
\n\n The most common correct answer was the readings should be repeated and an average taken. Another common answer was that D could be increased to reduce uncertainties in s. The best candidates knew that it was good practice to measure many fringe spacings and find the mean value. Quite a few candidates incorrectly stated that different apparatus should be used to give more precise results.\n
\n\n What is the variation of nuclear density\n \n ρ\n \n with nucleon number\n \n A\n \n ?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n \n Calculate the average power delivered to the ball during the impact.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n \n
\n\n \n \n \n \n \n ✔\n \n \n
\n\n \n \n \n \n \n «\n \n \n \n »\n \n \n \n \n \n \n ✔\n \n \n \n \n
\n\n
\n\n \n \n \n ALTERNATIVE 2\n \n \n \n
\n\n \n \n \n \n \n \n \n \n \n \n ✔\n \n \n \n \n \n
\n\n \n \n \n \n «\n \n \n \n \n \n »\n \n \n \n \n \n \n \n \n \n ✔\n \n \n \n \n
\n\n \n \n
\n\n This was well answered although a significant number of candidates approached it using P = Fv but forgot to divide v by 2 to calculated the average velocity. This scored one mark out of 2.\n
\n\n Draw the forces acting on the oil drop, ignoring the buoyancy force.\n
\n\n \n
\n [2]\n
\n\n Weight vertically down\n \n \n AND\n \n \n electric force vertically up ✓\n
\n\n Of equal length «by eye» ✓\n
\n\n Just before the loop is about to completely exit the region of magnetic field, the loop moves with constant terminal speed\n \n v\n \n .\n
\n\n The following data is available:\n
\n| \n Mass of loop\n | \n\n \n m\n \n = 4.0 g\n | \n
| \n Resistance of loop\n | \n\n \n R\n \n = 25 mΩ\n | \n
| \n Width of loop\n | \n\n \n L\n \n = 15 cm\n | \n
| \n Magnetic flux density\n | \n\n \n B\n \n = 0.80 T\n | \n
\n Determine, in m s\n \n −1\n \n the terminal speed\n \n v\n \n .\n
\n\n [4]\n
\n\n \n mg\n \n =\n \n BIL\n \n \n \n OR\n \n \n I = 0.33 «A» ✓\n
\n\n \n BvL\n \n =\n \n IR\n \n OR\n \n \n ℰ = 8.25 × 10\n \n −3\n \n «V»\n \n \n OR\n \n \n ℰ = 0.12\n \n v\n \n ✓\n
\n\n Combining results to get v =\n \n ✓\n
\n\n \n v\n \n = «\n \n =» 0.068 «m s\n \n −1\n \n »\n
\n\n \n Allow\n \n ECF\n \n between steps if clear work is shown.\n \n
\n\n A bird of weight\n \n \n \n sits on a thin rope at its midpoint. The rope is almost horizontal and has negligible mass.\n
\n\n \n
\n The tension in the rope is\n
\n\n
\n A. less than\n \n
\n B. equal to\n \n
\n\n C. between\n \n and\n \n
\n\n D. greater than\n \n
\n\n [1]\n
\n\n D\n
\n\n Theory predicts that\n
\n\n \n
\n\n where\n \n \n \n and\n \n are constants. The fundamental units of\n \n are m\n \n 4\n \n and those of\n \n E\n \n are kg m\n \n −1\n \n s\n \n −2\n \n .\n
\n\n Calculate\n \n and\n \n .\n
\n\n [2]\n
\n\n units of\n \n \n \n : kg m s\n \n −2\n \n ✓\n
\n\n work leading to\n \n and\n \n ✓\n
\n\n A cell of negligible internal resistance and electromotive force (emf) 6.0 V is connected to three resistors R, P and Q.\n
\n\n \n
\n R is an ohmic resistor. The\n \n I-V\n \n characteristics of P and Q are shown in the graph.\n
\n\n \n
\n The current in P is 0.40 A.\n
\n\n
\n\n Voltage across P is 1.4 «V» ✓\n
\n\n Voltage across Q is 4.6 «V» ✓\n
\n\n And 6 – 1.4 = 4.6 «V» ✓\n
\n\n
\n\n \n Need to see a calculation involving the two voltages and the total voltage in the circuit for\n \n MP3\n \n (e.g. 1.4 + 4.6 = 6).\n \n
\n\n Two long parallel wires X and Y carry equal currents\n \n I\n \n . The magnetic force exerted per unit length of each wire is\n \n \n \n .\n
\n\n The current in X is halved and the current in Y is doubled. What is the force per unit length of each wire after the change?\n
\n\n
\n| \n | \n\n \n Force per unit length of X\n \n | \n\n \n Force per unit length of Y\n \n | \n
| \n A.\n | \n\n \n | \n\n \n | \n
| \n B.\n | \n\n \n | \n\n \n | \n
| \n C.\n | \n\n \n | \n\n \n | \n
| \n D.\n | \n\n \n | \n\n \n | \n
\n [1]\n
\n\n A\n
\n\n \n T\n \n is measured with an electronic stopwatch that measures to the nearest 0.1 s.\n
\n\n Describe how an uncertainty in\n \n T\n \n of less than 0.1 s can be achieved using this stopwatch.\n
\n\n [2]\n
\n\n by measuring the time for many bounces ✓\n
\n\n and dividing the result by the number of bounces ✓\n
\n\n Plot on the diagram the position of P at time\n \n t\n \n = 0.50 s.\n
\n\n [1]\n
\n\n P at (8, 1.2) ✓\n
\n\n B is placed at the first minimum. The frequency is then changed until the received intensity is again at a maximum.\n
\n\n Show that the lowest frequency at which the intensity maximum can occur is about 3 kHz.\n
\n\n Speed of sound = 340 m s\n \n −1\n \n
\n\n [2]\n
\n\n «\n \n » = 13 cm ✓\n
\n\n \n «\n \n » 2.6 «kHz» ✓\n
\n\n
\n\n \n Allow ½ of wavelength from (b) or data from graph for\n \n MP1\n \n .\n \n
\n\n \n Allow ECF from\n \n MP1\n \n .\n \n
\n\n This was a \"show that\" question that had enough information for backwards working. Examiners were looking for evidence of using the wavelength from (b) or information from the graph to determine wavelength followed by a correct substitution and an answer to more significant digits than the given result.\n
\n\n Kepler’s Third law relates the orbital period\n \n \n \n of a planet about its sun to its orbital radius\n \n \n \n . The mass of the Sun is\n \n \n .\n \n
\n\n What is a correct algebraic form of the law?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Estimate, using the graph, the maximum height of the bottle.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Attempt to count squares ✓\n
\n\n Area of one square found ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4 m) ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n Uses area equation for either triangle ✓\n
\n\n Correct read offs for estimate of area of triangle ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4) ✓\n
\n\n Which of the following atomic energy level transitions corresponds to photons of the shortest wavelength?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n The most common (incorrect) response was A, where students apparently assumed energy difference was proportional to the wavelength of the emitted photon.\n
\n\n Calculate the angular impulse that acts on the propellor.\n
\n\n [2]\n
\n\n 190 rev s\n \n −1\n \n = 1190 rad s\n \n −1\n \n ✓\n
\n\n \n ✓\n
\n\n Explain why the new hypothesis is supported.\n
\n\n [1]\n
\n\n a «straight» line can be drawn that passes through origin ✓\n
\n\n determine the time taken for the detector to reach the muon source.\n
\n\n [1]\n
\n\n transit time =\n \n = 1.56\n \n µs\n \n ✓\n
\n\n
\n\n \n \n Award [1]\n \n for\n \n BCA\n \n .\n \n
\n\n The intensity of light at point O is\n \n . The distance OP is\n \n .\n
\n\n Sketch, on the axes, a graph to show the variation of the intensity of light with distance from point O on the screen. Your graph should cover the distance range from 0 to 2\n \n .\n
\n\n \n
\n [2]\n
\n\n smooth curve decreasing from\n \n to 0 between 0 and\n \n ✓\n
\n\n secondary maximum correctly placed\n \n \n AND\n \n \n of intensity less than 0.3\n \n ✓\n
\n\n \n E.g.\n \n \n
\n Most scored MP1. Many candidates scored full marks but it was common to see a maximum at 2x or a secondary maxima too high.\n
\n\n State, in terms of\n \n λ\n \n , the path length between points X and Z.\n
\n\n [1]\n
\n\n 4\n \n λ\n \n \n ✓\n \n
\n\n \n Show that the number of helium atoms in the container is 4 × 10\n \n 20\n \n .\n \n
\n\n [2]\n
\n\n \n \n \n \n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n \n \n \n \n ✔\n \n \n
\n\n
\n\n \n \n \n \n \n \n \n ✔\n \n \n \n \n
\n\n Again at HL this was very well answered with the most common approach being to calculate the number of moles and then multiply by N\n \n A\n \n to calculate the number of atoms. At SL many candidates calculated n but stopped there. Also at SL there was some evidence of candidates working backwards and magically producing a value for ‘n’ that gave a result very close to that required after multiplying by N\n \n A\n \n .\n
\n\n \n Calculate the ratio\n \n \n \n .\n \n
\n\n [1]\n
\n\n «\n \n \n \n \n »\n \n \n \n ✔\n \n
\n\n This was well answered with the most common mistake being to use the volume of a single atom rather than the total volume of the atoms.\n
\n\n Two cells are connected in parallel as shown below. Each cell has an emf of 5.0 V and an internal resistance of 2.0 Ω. The lamp has a resistance of 4.0 Ω. The ammeter is ideal.\n
\n\n What is the reading on the ammeter?\n
\n\n \n
\n A. 1.0 A\n
\n\n B. 1.3 A\n
\n\n C. 2.0 A\n
\n\n D. 2.5 A\n
\n\n [1]\n
\n\n A\n
\n\n The correct option (A) was selected with the lowest frequency of the four possible answers. This question has a low difficulty index, suggesting that the majority of candidates found it challenging. Students were asked to apply the concept of resistors in parallel; omitting the internal resistance in parallel to the external lamp resistance was the most common error here. This question is useful for the revision of resistors in combination.\n
\n\n the angular acceleration of the ring;\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «rad s\n \n −2\n \n » ✓\n
\n\n The student moves the screen closer to the double slit and repeats the measurements. The instruments used to make the measurements are unchanged.\n
\n\n Discuss the effect this movement has on the fractional uncertainty in the value of\n \n .\n
\n\n [2]\n
\n\n «As the measurements decrease» the fractional uncertainty in D/s increases. ✓\n
\n\n «Fractional uncertainties are additive here» so fractional uncertainty in\n \n increases ✓\n
\n\n \n Answers can be described in symbols e.g. Δs/s\n \n
\n\n The coefficient of dynamic friction between the block and the rough surface is 0.400.\n
\n\n Estimate the distance travelled by the block on the rough surface until it stops.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n Frictional force is\n \n f\n \n «= 0.400 × 2.40 × 9.81» = 9.42 «N» ✓\n
\n 9.42 ×\n \n d\n \n =\n \n × 2.40 × 2.16\n \n 2\n \n \n \n OR\n \n \n \n d\n \n =\n \n ✓\n
\n \n d\n \n = 0.594 «m» ✓\n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n \n a\n \n = «\n \n =\n \n µg\n \n = 0.4 × 9.81 =» 3.924 «m s\n \n −2\n \n » ✓\n
\n Proper use of kinematics equation(s) to determine ✓\n
\n\n \n d\n \n = 0.594 «m» ✓\n
\n\n \n Show that the pressure at B is about 130 kPa.\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n = 127 kPa\n \n ✔\n \n
\n\n \n A pure sample of a radioactive nuclide contains\n \n N\n \n \n 0\n \n atoms at time\n \n t\n \n = 0. At time\n \n t\n \n , there are\n \n N\n \n atoms of the nuclide remaining in the sample. The half-life of the nuclide is\n \n .\n \n
\n\n \n What is the decay rate of this sample proportional to?\n \n
\n\n
\n\n \n A.\n \n N\n \n \n
\n\n \n B.\n \n N\n \n \n 0\n \n –\n \n N\n \n \n
\n\n \n C.\n \n t\n \n \n
\n\n \n D.\n \n \n
\n\n [1]\n
\n\n A\n
\n\n Show that the temperature of the gas at C is approximately 350 °C.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n use of\n \n = constant «so\n \n » ✓\n
\n\n \n T\n \n \n C\n \n = 624 «K»\n \n \n OR\n \n \n \n T\n \n \n C\n \n = 351 «°C» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n use of\n \n to get either\n \n p\n \n \n c\n \n =\n \n \n \n OR\n \n \n \n p\n \n \n c\n \n = 268 «kPa» ✓\n
\n\n «\n \n T\n \n \n C\n \n = 268 × 300/129 = so »\n
\n\n \n T\n \n \n C\n \n = 624 «K»\n \n \n OR\n \n \n \n T\n \n \n C\n \n = 351 «°C» ✓\n
\n\n \n The temperature of a fixed mass of an ideal gas changes from 200 °C to 400 °C.\n
\n \n
\n \n What is\n \n \n \n \n \n ?\n
\n \n
\n \n A. 0.50\n
\n \n
\n \n B. 0.70\n
\n \n
\n \n C. 1.4\n
\n \n
\n \n D. 2.0\n \n
\n\n [1]\n
\n\n B\n
\n\n Most candidates chose A having forgotten to convert from oC to K.\n
\n\n A train is sounding its whistle when approaching a train station. Three statements about the sound received by a stationary observer at the station are:\n
\n\n I. The frequency received is higher than the frequency emitted by the train.\n
\n II. The wavelength received is longer than the wavelength emitted by the train.\n
\n III. The speed of the sound received is not affected by the motion of the train.\n
\n Which combination of statements is correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n A car has an initial speed of 16 m s\n \n −1\n \n . It decelerates at 4.0 m s\n \n −2\n \n until it stops.\n
\n\n What is the distance travelled by the car?\n
\n\n
\n A. 4 m\n
\n B. 16 m\n
\n\n C. 32 m\n
\n\n D. 64 m\n
\n\n [1]\n
\n\n C\n
\n\n Show that the equilibrium surface temperature of Titan is about 90 K.\n
\n\n [1]\n
\n\n \n σT\n \n \n 4\n \n = 3.07\n
\n\n \n \n OR\n \n \n
\n\n \n T\n \n = 86 «K» ✓\n
\n\n An interference pattern with minima of zero intensity is observed between light waves. What must be true about the frequency and amplitude of the light waves?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n This question was generally well answered by SL candidates with both a high difficulty and discrimination index. Candidates who selected an incorrect answer seems more certain about the correct amplitude than the resulting intensity.\n
\n\n Calculate the velocity component of the first curling stone in the initial direction.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n A negatively charged sphere is falling through a magnetic field.\n
\n\n \n
\n What is the direction of the magnetic force acting on the sphere?\n
\n\n
\n A. To the left of the page\n
\n B. To the right of the page\n
\n\n C. Out of the page\n
\n\n D. Into the page\n
\n\n [1]\n
\n\n D\n
\n\n The spacetime diagram shows an inertial reference frame S and a second inertial frame S’ that is moving relative to S.\n
\n\n The origins of the frames coincide when the clocks in both frames show zero.\n
\n\n \n
\n Event\n \n is shown for the S reference frame.\n
\n\n Which event occurs at the same position in the S’ reference frame as\n \n ?\n
\n\n [1]\n
\n\n C\n
\n\n Discuss, for this process, the changes that occur in the density of the gas.\n
\n\n [2]\n
\n\n density decreases ✓\n
\n\n volume is increased\n \n \n AND\n \n \n mass/number of particles remains constant ✓\n
\n\n A person stands in an elevator (lift). The total mass of the person and the elevator is 800 kg. The elevator accelerates upward at 2.0 m s\n \n −2\n \n .\n
\n\n \n
\n What is the tension in the cable?\n
\n\n
\n A. 1.6 kN\n
\n B. 6.4 kN\n
\n\n C. 8.0 kN\n
\n\n D. 9.6 kN\n
\n\n [1]\n
\n\n D\n
\n\n An electromagnetic wave has a wavelength that is about the size of the diameter of an atom.\n
\n\n What region of the electromagnetic spectrum does the wave belong to?\n
\n\n
\n A. Infrared\n
\n B. Visible light\n
\n\n C. Ultraviolet\n
\n\n D. X-ray\n
\n\n [1]\n
\n\n D\n
\n\n State the unit for\n \n pV\n \n in fundamental SI units.\n
\n\n [1]\n
\n\n kg m\n \n 2\n \n s\n \n −2\n \n ✓\n
\n\n Explain the changes to the rotational kinetic energy in the person-turntable system.\n
\n\n [2]\n
\n\n \n the rotational kinetic energy has increased\n \n \n ✓\n \n
\n\n \n energy is provided by the person doing work\n \n \n «\n \n \n flipping the wheel\n \n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n State the nucleon number of the He isotope that\n \n decays into.\n
\n\n [1]\n
\n\n 3 ✓\n
\n\n \n Do\n \n not\n \n accept\n \n by itself.\n \n
\n\n \n T\n \n \n t\n \n >\n \n T\n \n \n b\n \n
\n\n [2]\n
\n\n Conduction identified ✓\n
\n\n energy transfer through interaction of particles in liquid at atomic scale ✓\n
\n\n \n Suggest why this cycle is not a suitable model for a working heat pump.\n \n
\n\n [2]\n
\n\n \n the temperature changes in the cycle are too large ✔\n
\n \n
\n \n the cycle takes too long «because it contains an isothermal stage» ✔\n
\n \n
\n \n energy/power output would be too small ✔\n \n
\n\n Because the question was about a heat pump rather than a heat engine very few answers were correct. Only a very small number of candidates mentioned the fact that the isothermal change would take an impracticably long time.\n
\n\n What statement is\n \n not\n \n true about radioactive decay?\n
\n\n
\n A. The percentage of radioactive nuclei of an isotope in a sample of that isotope after 7 half-lives is smaller than 1 %.\n
\n B. The half-life of a radioactive isotope is the time taken for half the nuclei in a sample of that isotope to decay.\n
\n\n C. The whole-life of a radioactive isotope is the time taken for all the nuclei in a sample of that isotope to decay.\n
\n\n D. The half-life of radioactive isotopes range between extremely short intervals to thousands of millions of years.\n
\n\n [1]\n
\n\n C\n
\n\n There was some questioning about the use of the term 'whole-life' from teacher comments. As that option (C) was the correct answer and the most popular it did not confuse the candidates. The statement is clearly incorrect and the use of a non physics specific term that might be used in a general discussion was felt to be acceptable.\n
\n\n Which emission shows a continuous energy spectrum?\n
\n\n
\n A. Photons during energy transitions between atomic energy states\n
\n B. Gamma photons from the nuclei of radioactive isotopes\n
\n\n C. Beta particles from the nuclei of radioactive isotopes\n
\n\n D. Alpha particles from the nuclei of radioactive isotopes\n
\n\n [1]\n
\n\n C\n
\n\n Determine the speed of the spaceship relative to Earth.\n
\n\n [1]\n
\n\n 0.6 c\n
\n\n \n \n OR\n \n \n
\n\n = 1.8 × 10\n \n 8\n \n «m s\n \n −1\n \n » ✓\n
\n\n Outline why the wavelength of the photon has changed.\n
\n\n [2]\n
\n\n (Energy of photon inversely prop to wavelength)\n
\n\n
\n\n photon transfers some of its energy to the electron. ✓\n
\n\n If its energy decreases so its wavelength increases. ✓\n
\n\n A particle with charge −2.5 × 10\n \n −6\n \n C moves from point X to point Y due to a uniform electrostatic field. The diagram shows some equipotential lines of the field.\n
\n\n \n
\n What is correct about the motion of the particle from X to Y and the magnitude of the work done by the field on the particle?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n A ball of mass (50 ± 1) g is moving with a speed of (25 ± 1) m s\n \n −1\n \n . What is the fractional uncertainty in the momentum of the ball?\n
\n\n
\n A. 0.02\n
\n B. 0.04\n
\n\n C. 0.06\n
\n\n D. 0.08\n
\n\n [1]\n
\n\n C\n
\n\n A ray of monochromatic light is incident on the parallel interfaces between three media. The speeds of light in the media are\n \n v\n \n \n 1\n \n ,\n \n v\n \n \n 2\n \n and\n \n v\n \n \n 3\n \n .\n
\n\n \n
\n What is correct about the speeds of light in the media?\n
\n\n
\n A.\n \n v\n \n \n 3\n \n <\n \n v\n \n \n 1\n \n <\n \n v\n \n \n 2\n \n
\n B.\n \n v\n \n \n 3\n \n <\n \n v\n \n \n 2\n \n <\n \n v\n \n \n 1\n \n
\n\n C.\n \n v\n \n \n 2\n \n <\n \n v\n \n \n 3\n \n <\n \n v\n \n \n 1\n \n
\n\n D.\n \n v\n \n \n 2\n \n <\n \n v\n \n \n 1\n \n <\n \n v\n \n \n 3\n \n
\n\n [1]\n
\n\n D\n
\n\n The diagram below shows four energy levels for the atoms of a gas. The diagram is drawn to scale. The wavelengths of the photons emitted by the energy transitions between levels are shown.\n
\n\n \n
\n What are the wavelengths of spectral lines, emitted by the gas, in order of decreasing frequency?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The system is initially in configuration A. Comment, with reference to the second law of thermodynamics and your answer in (c), on the likely evolution of the system.\n
\n\n [3]\n
\n\n The second law predicts that isolated systems spontaneously evolve towards high-entropy states ✓\n
\n\n From (c), the entropy of B is greater than that of A ✓\n
\n\n The final state will likely be similar to B / contain relatively many low-energy particles «of different energies» ✓\n
\n\n In one particular event, a maximum emf of 65 mV is generated in the geophone. The geophone coil has 150 turns.\n
\n\n Calculate the rate of flux change that leads to this emf.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n \n
\n\n \n mWb s\n \n −1\n \n ✓\n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n A cyclist rides up a hill of vertical height 100 m in 500 s at a constant speed. The combined mass of the cyclist and the bicycle is 80 kg. The power developed by the cyclist is 200 W. What is the efficiency of the energy transfer in this system?\n
\n\n
\n\n A. 8 %\n
\n\n B. 20 %\n
\n\n C. 60 %\n
\n\n D. 80 %\n
\n\n [1]\n
\n\n D\n
\n\n An event has coordinates\n \n = 0 and\n \n ct\n \n = 0.60 ly in S. Show, using a Lorentz transformation, that the time coordinate of this event in S′ is\n \n ct\n \n ′ = 1.00 ly .\n
\n\n [2]\n
\n\n \n γ\n \n = 1.67\n \n \n OR\n \n \n \n \n \n OR\n \n \n \n ✓\n
\n\n \n ct\n \n ' = «\n \n γ\n \n (\n \n ct\n \n −\n \n )» =\n \n × (0.60 +0) ✓\n
\n\n «= 1.00 ly»\n
\n\n
\n\n \n For\n \n MP2\n \n , working should be seen.\n \n
\n\n \n Explain, using your answer to (d)(i) and with reference to the kinetic model, why this sample of helium can be assumed to be an ideal gas.\n \n
\n\n [2]\n
\n\n \n «For an ideal gas» the size of the particles is small compared to the distance between them/size of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» the volume of the particles is negligible/the volume of the particles is small compared to the volume of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» particles are assumed to be point objects ✔\n
\n \n
\n \n calculation/ratio/result in (d)(i) shows that volume of helium atoms is negligible compared to/much smaller than volume of helium gas/container «hence assumption is justified» ✔\n \n
\n\n In general this was poorly answered at SL. Many other non-related gas properties given such as no / negligible intermolecular forces, low pressure, high temperature. Some candidates interpreted the ratio as meaning it is a low density gas. At HL candidates seemed more able to focus on the key part feature of the question, which was the nature of the volumes involved. Examiners were looking for an assumption of the kinetic theory related to the volume of the atoms/gas and then a link to the ratio calculated in ci). The command terms were slightly different at SL and HL, giving slightly more guidance at SL.\n
\n\n State and explain the decay mode of\n \n .\n
\n\n [2]\n
\n\n beta minus decay ✓\n
\n\n \n has more neutrons / higher\n \n ratio than stable nuclides of similar\n \n A\n \n «and beta minus reduces\n \n » ✓\n
\n\n What are the fundamental SI units for angular impulse?\n
\n\n
\n A. kg m s\n \n −1\n \n
\n B. kg m\n \n 2\n \n s\n \n −1\n \n
\n\n C. kg m s\n \n −2\n \n
\n\n D. kg m\n \n 2\n \n s\n \n −2\n \n
\n\n [1]\n
\n\n B\n
\n\n \n An astronaut is moving at a constant velocity in the absence of a gravitational field when he throws a tool away from him.\n
\n \n
\n \n What is the effect of throwing the tool on the total kinetic energy of the astronaut and the tool and the total momentum of the astronaut and the tool?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n Outline, by reference to nuclear binding energy, why the mass of a nucleus is less than the sum of the masses of its constituent nucleons.\n
\n\n [2]\n
\n\n according to Δ\n \n E\n \n = Δ\n \n mc\n \n \n 2\n \n / identifies mass energy equivalence ✓\n
\n\n
\n\n energy is released when nucleons come together / a nucleus is formed «so nucleus has less mass than individual nucleons»\n
\n\n \n \n OR\n \n \n
\n\n energy is required to «completely» separate the nucleons / break apart a nucleus «so individual nucleons have more mass than nucleus» ✓\n
\n\n
\n\n \n Accept protons and neutrons.\n \n
\n\n Still several answers that thought that the nucleus needed to gain energy to bind it together. Most candidates scored at least one for recognising some form of mass/energy equivalence, although few candidates managed to consistently express their ideas here.\n
\n\n Calculate the speed of the combined masses immediately after the collision.\n
\n\n [1]\n
\n\n 0.40 «m s\n \n −1\n \n » ✔\n
\n\n Determine, using the graph, whether the gas acts as an ideal gas.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Graph shown is a straight line/linear\n
\n \n \n OR\n \n \n
\n expected graph should be a straight line/linear ✓\n
\n If ideal then\n \n T\n \n intercept must be at\n \n T\n \n = −273 °C ✓\n
\n\n Use of\n \n y\n \n =\n \n mx\n \n +\n \n c\n \n to show that\n \n x\n \n = −273 °C when\n \n y\n \n = 0 ✓\n
\n (hence ideal)\n
\n \n \n ALTERNATIVE 2\n \n \n
\n\n Calculates\n \n for two different points ✓\n
\n Obtains 1.50 «J K\n \n −1\n \n » for both ✓\n
\n States that for ideal gas\n \n which is constant and concludes that gas is ideal ✓\n
\n\n Describe\n \n two\n \n ways in which standing waves differ from travelling waves.\n
\n\n [2]\n
\n\n energy is not propagated by standing waves\n \n ✓\n \n
\n\n amplitude constant for travelling waves\n \n \n OR\n \n \n amplitude varies with position for standing waves\n \n \n OR\n \n \n standing waves have nodes/antinodes\n \n ✓\n \n
\n\n phase varies with position for travelling waves\n \n \n OR\n \n \n phase constant inter-node for standing waves\n \n ✓\n \n
\n\n travelling waves can have any wavelength\n \n \n OR\n \n \n standing waves have discrete wavelengths\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n Show that the energy released is about 18 MeV.\n
\n\n [2]\n
\n\n «𝜇» = 2.0141 + 3.0160 − (4.0026 + 1.008665) «= 0.0188 u»\n
\n\n \n \n OR\n \n \n
\n\n \n In\n \n MeV: 1876.13415 + 2809.404 − (3728.4219 + 939.5714475) ✓\n
\n\n
\n\n = 0.0188 × 931.5\n \n \n OR\n \n \n = 17.512 «MeV» ✓\n
\n\n
\n\n \n Must see either clear substitutions or answer to at least 3 s.f. for\n \n MP2\n \n .\n \n
\n\n State the fundamental SI units for permeability of free space,\n \n .\n
\n\n [1]\n
\n\n kg m s\n \n −2\n \n A\n \n −2\n \n ✓\n
\n\n Four resistors of\n \n each are connected as shown.\n
\n\n \n
\n What is the effective resistance between P and Q?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n This has a very low discrimination index. It is suspected that students did not realise that PQ has 2 branches in parallel and many chose D, 4 ohm, the value of a single resistor.\n
\n\n Show that the charge on the surface of the sphere is +18 μC.\n
\n\n [1]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n \n «μC» ✓\n
\n\n Calculate\n \n d\n \n .\n
\n\n [4]\n
\n\n distance difference\n \n m ✓\n
\n\n ½ distance difference\n \n m so YZ\n \n m ✓\n
\n\n \n ✓\n
\n\n
\n 29.8 m ✓\n
\n \n OR\n \n
\n\n Recognises situation as (almost) 3:4:5 triangle ✓\n
\n\n
\n 30 m (\n \n 1 sf answer only accepted in this route\n \n ) ✓\n
\n Draw the magnetic field lines due to A.\n
\n\n [2]\n
\n\n At least one circle centred on centre of wire A\n
\n \n \n AND\n
\n \n \n indication of clockwise direction ✓\n
\n More than 2 circles with increasing separation between circles from centre outwards (by eye) ✓\n
\n\n magnetic field at A;\n
\n\n [1]\n
\n\n Into the page ✓\n
\n\n Show that the speed of the wave on the string is about 240 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n \n Answer must be to 3 or more sf or working shown for\n \n MP2.\n \n \n
\n\n The average speed of the molecules of a gas is 500 m s\n \n −1\n \n . The density of the gas is 1.2 kg m\n \n −3\n \n . Calculate, in kPa, the pressure of the gas.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n 100 «kPa» ✓\n
\n\n Explain why the temperature of water remains at 100 °C during this time.\n
\n\n [1]\n
\n\n «all» of the energy added is used to increase the «intermolecular» potential energy of the particles/break «intermolecular» bonds/\n \n OWTTE\n \n \n ✓\n \n
\n\n \n Accept reference to atoms/molecules for “particle”\n \n
\n\n What is the relationship between the resistivity\n \n of a uniform wire, the radius\n \n of the wire and the length\n \n of the wire when its resistance is constant?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n It was pointed out on the G2s that the proportional symbol is incorrect. The high number of correct responses indicates that it did not disadvantage the students and will be corrected for publication.\n
\n\n Determine the charge\n \n of the sphere.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n
\n \n ✓\n \n
\n Even though many were able to choose the appropriate formula from the data booklet they were often hampered in their use of the formula by incorrect techniques when using fractions.\n
\n\n Calculate the total power dissipated in the circuit.\n
\n\n [1]\n
\n\n «0.45 × 6.0» = 2.7 «W»✓\n
\n\n The designers state that the energy transferred by the resistor every second is 15 J.\n
\n\n Calculate the current in the resistor.\n
\n\n [1]\n
\n\n \n I\n \n = «\n \n =» 1.9 «A» ✓\n
\n\n Sketch on the diagram the position of P at time\n \n t\n \n = 0.50 s.\n
\n\n [1]\n
\n\n P at (8, 1.2) ✓\n
\n\n The scale diagram shows the weight\n \n W\n \n of the mass at an instant when the rod is horizontal.\n
\n\n Draw, on the scale diagram, an arrow to represent the force exerted on the mass by the rod.\n
\n\n \n
\n [2]\n
\n\n horizontal component of any length to the left ✓\n
\n\n vertical component two squares long upwards ✓\n
\n\n E.g.\n
\n\n \n
\n
\n\n \n Ignore point of application.\n \n
\n\n \n Award\n \n [1]\n \n \n max\n \n if arrowhead not present.\n \n
\n\n Most just added the horizontal component. Not many centrifugal forces, but still a few. Very few were able to score both marks, so this question proved to be challenging for the candidates.\n
\n\n A fixed mass of an ideal gas expands slowly at constant temperature in a container.\n
\n\n Three statements about the gas molecules during the expansion are:\n
\n\n I. They collide with the walls of the container at a reduced rate.\n
\n II. They travel further on average between each collision.\n
\n III. Their average kinetic energy decreases as the gas expands.\n
\n Which statements are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n A\n
\n\n Explain why the magnitude of the force exerted on the mass by the rod is not constant.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n the net/centripetal force has constant magnitude ✓\n
\n\n the direction of the net/centripetal force constantly changes ✓\n
\n\n this is achieved by vector-adding weight and the force from the rod\n
\n\n \n \n OR\n \n \n
\n\n the force from the rod is vector difference of the centripetal force and weight ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n at the top F\n \n rod\n \n = F\n \n c\n \n − W ✓\n
\n\n at the bottom, F\n \n rod\n \n = F\n \n c\n \n + W ✓\n
\n\n net F/F\n \n c\n \n is constant so the force from the rod is different «hence is changing» ✓\n
\n\n
\n\n \n Accept reference to centripetal or net force indistinctly.\n \n
\n\n \n Allow reference to centripetal acceleration.\n \n
\n\n Many got into a bit of a mess with this one and it was quite difficult to interpret some of the answers. If they started out with the net/centripetal force being constant, then it was often easy to follow the reasoning. Starting with force on the rod varying often led to confusion. Quite a few did not pick up on the constant speed vertical circle so there were complicated energy/speed arguments to pick through.\n
\n\n An electron of non-relativistic speed\n \n interacts with an atom. All the energy of the electron is transferred to an emitted photon of frequency\n \n . An electron of speed\n \n now interacts with the same atom and all its energy is transmitted to a second photon. What is the frequency of the second photon?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Three historical developments in physics were\n
\n\n I. wave–particle duality\n
\n II. the kinetic model\n
\n III. the equivalence of mass and energy.\n
\n Which of these represented a paradigm shift in scientific thinking?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n \n The energy levels for an atom are shown to scale.\n \n
\n\n \n \n A photon of wavelength\n \n λ\n \n is emitted because of a transition from E\n \n 3\n \n to E\n \n 2\n \n . Which transition leads to the emission of a photon of longer wavelength?\n \n
\n \n A. E\n \n 4\n \n to E\n \n 1\n \n
\n \n
\n \n B. E\n \n 4\n \n to E\n \n 3\n \n
\n \n
\n \n C. E\n \n 3\n \n to E\n \n 1\n \n
\n \n
\n \n D. E2 to E\n \n 1\n \n \n
\n\n [1]\n
\n\n B\n
\n\n The highest and lowest temperatures of the gas during the cycle are 602 K and 92 K.\n
\n\n The efficiency of this engine is about 0.6. Outline how these data are consistent with the second law of thermodynamics.\n
\n\n [2]\n
\n\n \n e\n \n \n c\n \n = 1 −\n \n = 0.847 ✓\n
\n\n this engine has\n \n e\n \n <\n \n e\n \n \n c\n \n as it should ✓\n
\n\n
\n\n \n \n Award [0]\n \n if no calculation shown.\n \n
\n\n An electron enters a region of uniform magnetic field at a speed\n \n v\n \n . The direction of the electron is perpendicular to the magnetic field. The path of the electron inside the magnetic field is circular with radius\n \n r\n \n .\n
\n\n \n
\n The speed of the electron is varied to obtain different values of\n \n r\n \n .\n
\n\n Which graph represents the variation of speed\n \n v\n \n with\n \n r\n \n ?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n P and Q are two moons of equal densities orbiting a planet. The orbital radius of P is twice the orbital radius of Q. The volume of P is half that of Q. The force exerted by the planet on P is\n \n F\n \n . What is the force exerted by the planet on Q?\n
\n\n A.\n \n F\n \n
\n\n B. 2\n \n F\n \n
\n\n C. 4\n \n F\n \n
\n\n D. 8\n \n F\n \n
\n\n [1]\n
\n\n D\n
\n\n Option D was the most frequent (correct) answer, however option C was a significant distractor, perhaps for candidates considering only the change in orbital radius. A relatively high discrimination index was seen with this question.\n
\n\n Determine the wavelength of the incident photon.\n
\n\n [2]\n
\n\n Energy of incident photon =«\n \n »\n \n «eV» ✓\n
\n\n Wavelength of incident photon =«\n \n »\n \n «m» ✓\n
\n\n The graph shows the variation with time of the velocity of an object. Error bars for velocity are included.\n
\n\n \n
\n What is the percentage uncertainty for the velocity at time\n \n t\n \n = 4 s?\n
\n\n
\n A. ± 20 %\n
\n B. ± 10 %\n
\n\n C. ± 8 %\n
\n\n D. ± 5 %\n
\n\n
\n\n [1]\n
\n\n B\n
\n\n in its final orbit.\n
\n\n [1]\n
\n\n Positive ✓\n
\n\n \n Two forces of magnitude 12 N and 24 N act at the same point. Which force\n \n cannot\n \n be the resultant of these forces?\n
\n \n
\n \n A. 10 N\n
\n \n
\n \n B. 16 N\n
\n \n
\n \n C. 19 N\n
\n \n
\n \n D. 36 N\n \n
\n\n [1]\n
\n\n A\n
\n\n \n T\n \n \n t\n \n >\n \n T\n \n \n b\n \n
\n\n [2]\n
\n\n Conduction identified ✓\n
\n\n energy transfer through interaction of particles in liquid at atomic scale ✓\n
\n\n Outline the significance of conservation laws for physics.\n
\n\n [1]\n
\n\n they express fundamental principles of nature\n \n ✓\n \n
\n\n allow to model situations\n \n ✓\n \n
\n\n allow to calculate unknown variables\n \n ✓\n \n
\n\n allow to predict possible outcomes\n \n ✓\n \n
\n\n allow to predict missing quantities/particles\n \n ✓\n \n
\n\n allow comparison of different system states\n \n ✓\n \n
\n\n \n A substance changes from the solid phase to the gas phase without becoming a liquid and without a change in temperature.\n
\n \n
\n \n What is true about the internal energy of the substance and the total intermolecular potential energy of the substance when this phase change occurs?\n \n
\n\n \n \n \n
\n [1]\n
\n\n C\n
\n\n This question has a low discrimination index at SL with more candidates choosing response D rather than the correct C. Candidates should remember that all information given in the question is important and the clue here is ‘without a change in temperature’. Thus the kinetic energy does not change so internal energy and potential energy will both have the same change and in addition energy must be provided to change the state of a solid.\n
\n\n The slits are separated by a distance of 0.18 mm and the distance to the screen is 2.2 m. Determine, in m, the wavelength of light.\n
\n\n [2]\n
\n\n Use of\n \n s\n \n =\n \n =\n \n \n \n OR\n \n \n \n s\n \n =\n \n =\n \n ✓\n
\n\n \n = «\n \n =» 4.6 × 10\n \n −7\n \n «m» ✓\n
\n\n Draw, on the axes, the variation of electric potential\n \n with distance\n \n from the centre of the sphere.\n
\n\n \n
\n [2]\n
\n\n \n curve decreasing asymptotically for\n \n \n \n ✓\n \n
\n\n \n non\n \n zero constant between\n \n and\n \n \n \n \n \n ✓\n \n
\n\n \n
\n This was well answered.\n
\n\n Explain the pattern seen on the screen.\n
\n\n [3]\n
\n\n Mention of interference / superposition ✓\n
\n\n Bright fringe occurs when light from the slits arrives in phase ✓\n
\n\n Dark fringe occurs when light from the slits arrives 180°/\n \n out of phase ✓\n
\n\n Calculate the power transferred by the heater when both switches are closed.\n
\n\n [2]\n
\n\n use of parallel resistors addition so\n \n R\n \n \n eq\n \n = 15 «Ω»\n \n ✓\n \n
\n\n \n P\n \n = 3200 «W»\n \n ✓\n \n
\n\n Three statements about the Carnot cycle are:\n
\n\n I. The Carnot cycle is reversible.\n
\n II. The net entropy change of the surroundings of the gas over one cycle is positive.\n
\n III. Heat transfer takes place in only two stages of the cycle\n
\n Which statements are correct?\n
\n\n
\n A. I and II\n
\n B. I and III\n
\n\n C. II and III\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n \n Discuss, by reference to the kinetic model of an ideal gas and the answer to (c)(i), whether the assumption that helium behaves as an ideal gas is justified.\n \n
\n\n [2]\n
\n\n \n «For an ideal gas» the size of the particles is small compared to the distance between them/size of the container/gas\n \n
\n\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» the volume of the particles is negligible/the volume of the particles is small compared to the volume of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» particles are assumed to be point objects ✔\n \n
\n\n \n calculation/ratio/result in (c)(i) shows that volume of helium atoms is negligible compared to/much smaller than volume of helium gas/container «hence assumption is justified» ✔\n \n
\n\n At HL candidates seemed more able to focus on the key part feature of the question, which was the nature of the volumes involved. Examiners were looking for an assumption of the kinetic theory related to the volume of the atoms/gas and then a link to the ratio calculated in ci). The command terms were slightly different at SL and HL, giving slightly more guidance at SL.\n
\n\n Calculate\n \n d\n \n .\n
\n\n [4]\n
\n\n distance difference\n \n m ✓\n
\n\n ½ distance difference\n \n m so YZ\n \n m ✓\n
\n\n \n ✓\n
\n\n
\n 29.8 m ✓\n
\n \n OR\n \n
\n\n Recognises situation as (almost) 3:4:5 triangle ✓\n
\n\n
\n 30 m (\n \n 1 sf answer only accepted in this route\n \n ) ✓\n
\n State the unit for\n \n pV\n \n in fundamental SI units.\n
\n\n [1]\n
\n\n kg m\n \n 2\n \n s\n \n −2\n \n ✓\n
\n\n \n Explain why the path of the proton is a circle.\n \n
\n\n [2]\n
\n\n \n magnetic force is to the left «at the instant shown»\n
\n \n \n OR\n \n \n
\n explains a rule to determine the direction of the magnetic force ✔\n \n
\n \n force is perpendicular to velocity/«direction of» motion\n
\n \n \n OR\n \n \n
\n force is constant in magnitude ✔\n \n
\n \n force is centripetal/towards the centre ✔\n \n
\n\n \n \n NOTE: Accept reference to acceleration instead of force\n \n \n
\n\n Show that the speed of the loop is 20 cm s\n \n −1\n \n .\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Outline how a standing wave forms in the tube.\n
\n\n [2]\n
\n\n «sound» wave «travels down tube and» is reflected\n \n ✓\n \n
\n\n incident and reflected wave superpose/combine/interfere\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n \n Do not award\n \n MP1\n \n if the reflection is quoted at the walls/container\n \n
\n\n The theoretical relationship assumes that the ball is only affected by the electric force.\n
\n\n Suggest why, in order to test the relationship, the length of the string should be much greater than the distance between the plates.\n
\n\n [2]\n
\n\n the angle between the string and the vertical should be very small «for any position of the ball» ✓\n
\n\n so that the tension in the string is «almost» balanced by the ball’s weight\n
\n\n \n \n OR\n \n \n
\n\n restoring force from the string / horizontal component of tension negligibly small «compared with electric force» ✓\n
\n\n \n OWTTE\n \n
\n\n Calculate the number of gas particles in the cylinder.\n
\n\n [2]\n
\n\n Correct conversion of T «T = 310 K» seen ✓\n
\n\n « use of =\n \n to get » 2.3 × 10\n \n 23\n \n ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n i.e., T in Celsius (Result is 2.7 x 10\n \n 24\n \n )\n \n
\n\n \n Allow use of n, R and N\n \n A\n \n \n
\n\n a) This was well answered with the majority converting to K. Quite a few found the number of moles but did not then convert to molecules.\n
\n\n bi) Well answered. It was pleasing to see how many recognised the need to state that the mass/number of molecules stayed the same as well as stating that the volume increased. At SL this recognition was less common so only 1 mark was often awarded.\n
\n\n bii) This was less successfully answered. A surprising number of candidates said that the internal energy of an ideal gas increases during an isothermal expansion. Many recognised that constant temp meant constant KE but then went on to state that the PE must increase and so the internal energy would increase.\n
\n
\n
\n \n Calculate the additional intensity that must be lost by the oceans so that the water temperature remains constant.\n \n
\n\n [2]\n
\n\n \n water loses 396\n \n −\n \n 330/66 «\n \n W m\n \n \n \n −\n \n 2\n \n » ✔\n
\n \n
\n \n extra intensity that must be lost is\n \n «\n \n 170\n \n −\n \n 66\n \n »\n \n = 104\n \n ≈\n \n 100 «\n \n W m\n \n \n \n −\n \n 2\n \n » ✔\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n absorbed by water 330\n \n +\n \n 170/500 «\n \n W m\n \n \n \n −\n \n 2\n \n »✔\n
\n \n
\n \n extra intensity that must be lost is\n \n «\n \n 500\n \n −\n \n 396\n \n »\n \n = 104\n \n ≈\n \n 100 «\n \n W m\n \n \n \n −\n \n 2\n \n » ✔\n \n
\n\n This was well-answered, a very straightforward 2 marks.\n
\n\n \n A block of weight\n \n W\n \n slides down a ramp at constant velocity. A friction force\n \n F\n \n acts between the bottom of the block and the surface of the ramp. A normal reaction\n \n N\n \n acts between the ramp and the block. What is the free-body diagram for the forces that act on the block?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n Calculate the gradient of the graph.\n
\n\n [2]\n
\n\n large enough triangle Δ\n \n m\n \n ≥ 50 g✓\n
\n\n answer in range 0.210 − 0.240 «kg m\n \n −1\n \n » ✓\n
\n\n
\n\n \n Accept answers in g m\n \n −2\n \n .\n \n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n The bob of a pendulum has an initial displacement\n \n to the right. The bob is released and allowed to oscillate. The graph shows how the displacement varies with time. At which point is the velocity of the bob at its maximum magnitude directed towards the left?\n
\n\n \n
\n
\n\n [1]\n
\n\n C\n
\n\n Outline what is meant by an isotope.\n
\n\n [1]\n
\n\n «An atom with» the same number of protons\n \n \n AND\n \n \n different numbers of neutrons\n
\n \n \n OR\n \n \n
\n Same chemical properties\n \n \n AND\n \n \n different physical properties ✓\n
\n \n Do\n \n not\n \n allow just atomic number and mass number\n \n
\n\n A charged rod is brought near an initially neutral metal sphere without touching it.\n
\n\n When the sphere is grounded (earthed), there is an electric current for a short time from the sphere to the ground.\n
\n\n \n
\n The ground connection is then removed.\n
\n\n What are the charge on the rod and the charge induced on the sphere when the connection is removed?\n
\n
\n
\n \n
\n [1]\n
\n\n C\n
\n\n For a thermodynamic process, the entropy of the universe\n
\n\n
\n A. always increases during the process\n
\n B. depends only on energy transferred during the process\n
\n\n C. is zero during the process\n
\n\n D. never decreases during the process\n
\n\n [1]\n
\n\n D\n
\n\n After the load has hit the floor, the box travels a further 0.35 m along the ramp before coming to rest. Determine the average frictional force between the box and the surface of the ramp.\n
\n\n [4]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «\n \n » leading to\n \n a\n \n = 6.3 «m s\n \n -2\n \n »\n
\n\n \n \n OR\n \n \n
\n\n «\n \n » leading to\n \n t\n \n = 0.33 « s » ✓\n
\n\n \n
\n \n \n F\n \n \n net\n \n = «\n \n = » 9.45 «N» ✓\n
\n Weight down ramp = 1.5 x 9.8 x sin(30) = 7.4 «N» ✓\n
\n\n friction force = net force – weight down ramp = 2.1 «N» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n kinetic energy initial = work done to stop 0.5 x 1.5 x (2.1)\n \n 2\n \n =\n \n F\n \n \n NET\n \n x 0.35 ✓\n
\n\n \n F\n \n \n net\n \n = 9.45 «N» ✓\n
\n\n Weight down ramp = 1.5 x 9.8 x sin(30) = 7.4 «N» ✓\n
\n\n friction force = net force – weight down ramp = 2.1 «N» ✓\n
\n\n
\n\n \n Accept 1.95 N from g = 10\n \n m s\n \n -2\n \n \n .\n \n
\n \n Accept 2.42 N from u = 2.14\n \n m s\n \n -1\n \n \n .\n \n
\n Candidates struggled with this question. Very few drew a clear free-body diagram and many simply calculated the acceleration of the box from the given information and used this to calculate the net force on the box, confusing this with the frictional force.\n
\n\n A beta-minus particle and an alpha particle have the same initial kinetic energy.\n
\n\n Outline why the beta-minus particle can travel further in air than the alpha particle.\n
\n\n [2]\n
\n\n Alphas have double charge «and so are better ionisers »✓\n
\n\n alphas have more mass and therefore slower «for same energy» ✓\n
\n\n so longer time/more likely to interact with the «atomic» electrons/atoms «and therefore better ionisers» ✓\n
\n\n \n Accept reverse argument in terms of betas travelling faster.\n \n
\n\n \n A nuclear particle has an energy of 10\n \n 8\n \n eV. A grain of sand has a mass of 32 mg. What speed must the grain of sand have for its kinetic energy to equal the energy of the nuclear particle?\n \n
\n\n \n A. 1 mm s\n \n –1\n \n
\n \n
\n \n B. 3 mm s\n \n –1\n \n
\n \n
\n \n C. 10 mm s\n \n –1\n \n
\n \n
\n \n D. 16 mm s\n \n –1\n \n \n
\n\n [1]\n
\n\n A\n
\n\n A substance in the gas state has a density about\n \n times less than when it is in the liquid state. The diameter of a molecule is\n \n . What is the best estimate of the average distance between molecules in the gas state?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n This question gives good discrimination at HL but less so at SL. Teacher comments felt that the question was too mathematical but it can be noted that it asks for an estimation of the average distance which is related to the cube root of the volume and 1000 is 103. At both levels option D proved a popular alternative suggesting that candidates were forgetting the cube root.\n
\n\n In the decay of polonium−210, alpha emissions can be accompanied by the emissions of gamma photons, all of the same wavelength of 1.54 × 10\n \n −12\n \n m.\n
\n\n Discuss how this observation provides evidence for discrete nuclear energy levels.\n
\n\n [3]\n
\n\n photon energy is determined by its wavelength ✓\n
\n\n
\n photons are emitted when nucleus undergoes transitions between its «nuclear» energy levels\n
\n \n \n OR\n \n \n
\n\n photon energy equals the difference between «nuclear» energy levels ✓\n
\n\n
\n photons have the same energy / a fixed value\n
\n \n \n OR\n \n \n
\n\n energy is quantized / discrete ✓\n
\n\n Many identified conservation of momentum and consequently the relative velocities but it was common to miss MP3 for correctly relating this to KE.\n
\n\n the initial temperature gradient through the base of the pot. State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n K m\n \n −1\n \n ✓\n
\n\n \n Calculate the time it takes the tennis ball to reach the net.\n \n
\n\n [2]\n
\n\n \n horizontal component of velocity is\n \n \n \n «\n \n \n \n » ✔\n
\n \n
\n \n \n \n \n \n \n «\n \n \n \n »\n \n \n \n «\n \n \n \n » ✔\n \n \n \n
\n\n
\n\n This question scored well at HL but less so at SL. One common mistake was to calculate the direct distance to the top of the net and assume that the ball travelled that distance with constant speed. At SL particularly, another was to consider the motion only when the ball is in contact with the racquet.\n
\n\n Draw the absolute uncertainty determined in part (d)(i) as an error bar on the graph.\n
\n\n [1]\n
\n\n error bar drawn at 30 kPa from 34 × 10\n \n 5\n \n to 46 × 10\n \n 5\n \n N\n \n 3\n \n ✓\n
\n\n \n
\n Allow ± half square on each side of the bar or one square overall (± 2 × 10\n \n 5\n \n )\n \n
\n \n Allow\n \n ECF\n \n from\n \n d(i)\n \n .\n \n
\n\n Determine the magnitude and direction of the resultant magnetic field at Q.\n
\n\n [2]\n
\n\n «using components or Pythagoras to get»\n \n B\n \n = 21 «mT» ✓\n
\n\n directed «horizontally» to the right ✓\n
\n\n
\n\n \n If no unit seen, assume\n \n mT.\n
\n\n State what is meant by an ideal voltmeter.\n
\n\n [1]\n
\n\n infinite resistance\n
\n\n \n \n OR\n \n \n
\n\n no current is flowing through it ✓\n
\n\n A majority of candidates scored a mark by simply stating infinite resistance. Several answers went the other way round, stating a resistance of zero.\n
\n\n State what will happen to the angular position of the primary maxima.\n
\n\n [1]\n
\n\n stays the same ✓\n
\n\n Planets X and Y orbit the same star.\n
\n\n The average distance between planet X and the star is five times greater than the average distance between planet Y and the star.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Determine\n \n v\n \n \n A\n \n . State the answer in terms of\n \n v\n \n .\n
\n\n [3]\n
\n\n Energy is conserved hence\n \n ✓\n
\n\n Eliminate\n \n using the result of part (a), e.g.,\n \n ✓\n
\n\n \n ✓\n
\n\n Calculate the initial kinetic energy of the cannon.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Calculate the thermal energy (heat) taken out of the gas from B to C.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n ✓\n
\n\n \n «\n \n × 3.33 × 10\n \n −2\n \n × (3.00 × 10\n \n 4\n \n − 4.60 × 10\n \n 3\n \n )» = 1268.7 ≈ 1270 «J» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n .\n \n
\n\n \n Accept negative values.\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n \n \n OR\n \n \n \n T\n \n c\n \n \n = 4.6 × 10\n \n 3\n \n × 3.33 × 10\n \n −2\n \n × 1.66 = 92.2 ✓\n
\n\n \n «J» ✓\n
\n\n
\n\n \n Award\n \n MP1\n \n if T\n \n c\n \n = 92 taken from\n \n (e)\n \n \n
\n\n The background count in a laboratory is 20 counts per second. The initial observed count rate of a pure sample of nitrogen-13 in this laboratory is 180 counts per second. The half-life of nitrogen-13 is 10 minutes. What is the expected count rate of the sample after 30 minutes?\n
\n\n A. 20 counts per second\n
\n\n B. 23 counts per second\n
\n\n C. 40 counts per second\n
\n\n D. 60 counts per second\n
\n\n [1]\n
\n\n C\n
\n\n Option B was the most frequent answer, incorrectly selected by candidates who did not consider the background count in the laboratory.\n
\n\n A person is standing at rest on the ground and experiences a downward gravitational force\n \n W\n \n and an upward normal force from the ground\n \n N\n \n . Which, according to Newton’s third law, is the force that together with\n \n W\n \n forms a force pair?\n
\n\n A. The gravitational force\n \n W\n \n acting upwards on the ground.\n
\n\n B. The gravitational force\n \n W\n \n acting upwards on the person.\n
\n\n C. The normal force\n \n N\n \n acting upwards on the person.\n
\n\n D. The normal force\n \n N\n \n acting downwards on the ground.\n
\n\n [1]\n
\n\n A\n
\n\n Calculate the power dissipated in the circuit.\n
\n\n [1]\n
\n\n power\n \n \n ✓\n \n
\n\n A straightforward calculation question that most candidates answered correctly.\n
\n\n In science, models are extensively used to study real life situations.\n
\n\n A person X on the beach wants to reach a person Y in the sea in the shortest possible time. The speed of person X on land is different from the speed of person X in the water. Which physical phenomenon will best model the path with the least time?\n
\n\n \n
\n
\n\n A. Conservation of momentum\n
\n\n B. Diffraction\n
\n\n C. Flow of charge in a conductor\n
\n\n D. Refraction\n
\n\n [1]\n
\n\n D\n
\n\n Explain, by reference to charge carriers in the wire, how the magnetic force on the wire arises.\n
\n\n [2]\n
\n\n charge/carriers are moving in a magnetic field ✓\n
\n\n
\n\n there is a magnetic force on them / quote\n \n F = qvB\n \n
\n\n \n \n OR\n \n \n
\n\n this creates a magnetic field that interacts with the external magnetic field ✓\n
\n\n
\n\n \n Accept electrons.\n \n
\n\n \n For\n \n MP2\n \n , the force must be identified as acting on charge / carriers.\n \n
\n\n Many scored MP1 here but did not get MP2 as they jumped straight to the wire rather than continuing with the explanation of what was going on with the charge carriers.\n
\n\n The system rotates from rest and reaches a maximum angular speed of 20 rad s\n \n −1\n \n in a time of 5.0 s. Calculate the angular acceleration of the system.\n
\n\n [1]\n
\n\n «α =\n \n =» 4 «rad s\n \n −2\n \n » ✓\n
\n\n The player kicks the ball again. It rolls along the ground without sliding with a horizontal velocity of\n \n . The radius of the ball is\n \n . Calculate the angular velocity of the ball. State an appropriate SI unit for your answer.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n \n
\n Unit must be seen for mark\n \n
\n \n Accept Hz\n \n
\n\n \n Accept\n \n \n
\n\n Most power stations rely on a turbine and a generator to produce electrical energy. Which power station works on a different principle?\n
\n\n A. Nuclear\n
\n\n B. Solar\n
\n\n C. Fossil fuel\n
\n\n D. Wind\n
\n\n [1]\n
\n\n B\n
\n\n A stone of mass\n \n m\n \n is projected vertically upwards with speed\n \n u\n \n from the top of a cliff. The speed of the stone when it is just about to hit the ground is\n \n v\n \n .\n
\n\n \n
\n What is the magnitude of the change in momentum of the stone?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n The smallest mass of magnesium that can be detected with this technique is 1.1 × 10\n \n −8\n \n kg.\n
\n\n Show that the smallest number of magnesium atoms that can be detected with this technique is about 10\n \n 17\n \n .\n
\n\n [2]\n
\n\n So 1.1 × 10\n \n −8\n \n kg ≡\n \n × 10\n \n −8\n \n «mol»\n
\n\n \n \n OR\n \n \n
\n\n Mass of atom = 27 × 1.66 × 10\n \n −27\n \n «kg» ✓\n
\n\n 2.4 − 2.5 x 10\n \n 17\n \n atoms ✓\n
\n\n \n Explain why the kinetic energy of the proton is constant.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n
\n work done by force is change in kinetic energy ✔\n
\n work done is zero/force perpendicular to velocity ✔\n
\n \n
\n \n \n NOTE: Award\n \n [2]\n \n for a reference to work done is zero hence E\n \n k\n \n remains constant\n \n
\n \n
\n
\n\n \n \n \n ALTERNATIVE 2\n \n \n
\n proton moves at constant speed ✔\n
\n kinetic energy depends on speed ✔\n
\n \n
\n \n \n NOTE: Accept mention of speed or velocity indistinctly in MP2\n \n
\n \n
\n
\n\n Explain why the new hypothesis is supported.\n
\n\n [1]\n
\n\n a «straight» line can be drawn that passes through origin ✓\n
\n\n A planet has an albedo of 0.30. A simplified energy balance for the planet is shown.\n
\n\n \n
\n What is the intensity radiated by the surface of the planet?\n
\n\n
\n A. 70 W m\n \n −2\n \n
\n B. 90 W m\n \n −2\n \n
\n\n C. 100 W m\n \n −2\n \n
\n\n D. 130 W m\n \n −2\n \n
\n\n [1]\n
\n\n D\n
\n\n Discuss the mechanism that accounts for the greatest rate of energy transfer when:\n
\n\n
\n\n Conduction identified ✓\n
\n\n energy transfer through interaction of particles in liquid at atomic scale ✓\n
\n\n The ratio of the diameter of an atom to the diameter of its nucleus is:\n
\n\n
\n A. 10\n \n 1\n \n
\n B. 10\n \n 3\n \n
\n\n C. 10\n \n 5\n \n
\n\n D. 10\n \n 7\n \n
\n\n [1]\n
\n\n C\n
\n\n \n V\n \n is provided by two identical power supplies connected in series. The potential difference of each of the power supplies is known with an uncertainty of 0.01 kV.\n
\n\n State the uncertainty in the potential difference\n \n V\n \n .\n
\n\n [1]\n
\n\n 0.02 «kV» ✓\n
\n\n Wire XY moves perpendicular to a magnetic field in the direction shown.\n
\n\n \n
\n The graph shows the variation with time of the displacement of XY.\n
\n\n \n
\n What is the graph of the electromotive force (emf)\n \n ε\n \n induced across XY?\n
\n\n
\n \n
\n [1]\n
\n\n C\n
\n\n What is the order of magnitude of the wavelength of visible light?\n
\n\n A. 10\n \n −10\n \n m\n
\n\n B. 10\n \n −7\n \n m\n
\n\n C. 10\n \n −4\n \n m\n
\n\n D. 10\n \n −1\n \n m\n
\n\n [1]\n
\n\n B\n
\n\n This question was correctly answered by the majority of SL candidates.\n
\n\n The temperature of the sample is increased without a change in pressure. Outline the effect it has on the density of the gas.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n The average translational speed increases «because\n \n T\n \n increases» ✓\n
\n\n From\n \n , the density decreases «to keep\n \n \n \n constant» ✓\n
\n\n
\n \n \n ALTERNATIVE 2\n \n \n
\n From the ideal gas law, the volume of the gas increases ✓\n
\n\n Since\n \n and\n \n \n \n is constant, the density decreases ✓\n
\n\n The theoretical relationship assumes that the ball is only affected by the electric force.\n
\n\n Suggest why, in order to test the relationship, the length of the string should be much greater than the distance between the plates.\n
\n\n [2]\n
\n\n the angle between the string and the vertical should be very small «for any position of the ball» ✓\n
\n\n so that the tension in the string is «almost» balanced by the ball’s weight\n
\n\n \n \n OR\n \n \n
\n\n restoring force from the string / horizontal component of tension negligibly small «compared with electric force» ✓\n
\n\n \n OWTTE\n \n
\n\n Monochromatic light is incident on a metal surface and electrons are released. The intensity of the incident light is increased. What changes, if any, occur to the rate of emission of electrons and to the kinetic energy of the emitted electrons?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n The student changes the light source to one that emits two colours:\n
\n • blue light of wavelength\n \n , and\n
\n • red light of wavelength 1.5\n \n .\n
\n Predict the pattern that the student will see on the screen.\n
\n\n [3]\n
\n\n Blue fringe is unchanged ✓\n
\n\n Red fringes are farther apart than blue ✓\n
\n\n By a factor of 1.5 ✓\n
\n\n At some point/s the fringes coincide/are purple ✓\n
\n\n A mass is oscillating with simple harmonic motion. At time\n \n t\n \n , the acceleration is at a positive maximum.\n
\n\n What are the displacement and velocity of the mass at time\n \n t\n \n ?\n
\n\n
\n| \n | \n\n \n Displacement\n \n | \n\n \n Velocity\n \n | \n
| \n A.\n | \n\n positive maximum\n | \n\n zero\n | \n
| \n B.\n | \n\n negative maximum\n | \n\n zero\n | \n
| \n C.\n | \n\n positive maximum\n | \n\n negative maximum\n | \n
| \n D.\n | \n\n negative maximum\n | \n\n negative maximum\n | \n
\n [1]\n
\n\n B\n
\n\n \n Show that the average force exerted on the ball by the racket is about 50 N.\n \n
\n\n [2]\n
\n\n use of Δ\n \n t =\n \n \n «\n \n (28 – 12) × 10\n \n –3\n \n =\n \n »\n \n 16 × 10\n \n –3\n \n \n «\n \n s\n \n »\n \n ✔\n \n \n
\n\n \n \n \n =«\n \n »\n \n \n \n OR\n \n \n 53 «N» ✔\n \n \n
\n\n \n \n \n NOTE: Accept a time interval from 14 to 16\n \n \n \n \n \n ms\n \n \n \n \n \n
\n Allow ECF from incorrect time interval\n \n \n \n
\n \n Determine the speed of the tennis ball as it strikes the ground.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n
\n \n \n
\n \n Initial KE + PE = final KE /\n \n
\n\n \n \n \n \n × 0.058 × 64\n \n 2\n \n + 0.058 × 9.81 × 2.80 =\n \n \n \n \n \n \n ×\n \n 0.058\n \n ×\n \n \n v\n \n \n 2\n \n ✔\n
\n \n
\n \n \n v\n \n = 64.4 «\n \n ms\n \n −1\n \n \n » ✔\n \n \n
\n \n
\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n
\n \n \n \n \n »\n \n ✔\n \n \n
\n\n \n «\n \n \n \n »\n \n
\n\n \n \n \n \n \n »\n \n ✔\n \n \n \n
\n\n \n \n \n \n
\n\n This proved difficult for candidates at both HL and SL. Many managed to calculate the final vertical component of the velocity of the ball.\n
\n\n The highest and lowest temperatures of the gas during the cycle are 602 K and 92 K.\n
\n\n The efficiency of this engine is about 0.6. Outline how these data are consistent with the second law of thermodynamics.\n
\n\n [2]\n
\n\n \n e\n \n \n c\n \n = 1 −\n \n = 0.847 ✓\n
\n\n this engine has\n \n e\n \n <\n \n e\n \n \n c\n \n as it should ✓\n
\n\n
\n\n \n \n Award [0]\n \n if no calculation shown.\n \n
\n\n Deduce the current in R.\n
\n\n [2]\n
\n\n The force on Q due to R must have the same magnitude «but opposite direction» as the force on Q due to P ✓\n
\n\n The distance is halved therefore one half of the current is needed to produce the same force, so 2.5 A ✓\n
\n\n Just before the loop is about to completely exit the region of magnetic field, the loop moves with constant terminal speed\n \n v\n \n .\n
\n\n The following data is available:\n
\n| \n Mass of loop\n | \n\n \n m\n \n = 4.0 g\n | \n
| \n Resistance of loop\n | \n\n \n R\n \n = 25 mΩ\n | \n
| \n Width of loop\n | \n\n \n L\n \n = 15 cm\n | \n
| \n Magnetic flux density\n | \n\n \n B\n \n = 0.80 T\n | \n
\n Determine, in m s\n \n −1\n \n the terminal speed\n \n v\n \n .\n
\n\n [4]\n
\n\n \n mg\n \n =\n \n BIL\n \n \n \n OR\n \n \n I = 0.33 «A» ✓\n
\n\n \n BvL\n \n =\n \n IR\n \n OR\n \n \n ℰ = 8.25 × 10\n \n −3\n \n «V»\n \n \n OR\n \n \n ℰ = 0.12\n \n v\n \n ✓\n
\n\n Combining results to get v =\n \n ✓\n
\n\n \n v\n \n = «\n \n =» 0.068 «m s\n \n −1\n \n »\n
\n\n \n Allow\n \n ECF\n \n between steps if clear work is shown.\n \n
\n\n On the diagram draw an arrow to show the direction of the magnetic field at Q due to wire X\n \n alone\n \n .\n
\n\n [1]\n
\n\n
\n\n \n
\n arrow of any length as shown ✓\n
\n\n State and explain the number of microstates of the system in configuration A.\n
\n\n [2]\n
\n\n 6 microstates ✓\n
\n\n Any of the six particles can be the one of the highest energy ✓\n
\n\n State, in terms of\n \n λ\n \n , the path length between points X and Z.\n
\n\n [1]\n
\n\n 4\n \n λ\n \n \n ✓\n \n
\n\n The mass of the bottle is 27 g and it is in contact with the ground for 85 ms.\n
\n\n Determine the average force exerted by the ground on the bottle. Give your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n Attempt to use force = momentum change ÷ time ✓\n
\n\n «=\n \n = 4.6»\n
\n\n Force = «4.6 + 0.3» 4.9 «N» ✓\n
\n\n Any answer to 2sf ✓\n
\n\n \n Accept ± 0.5 velocity values from graph\n \n
\n\n An object is sliding from rest down a frictionless inclined plane. The object slides 1.0 m during the first second.\n
\n\n \n
\n What distance will the object slide during the next second?\n
\n\n A. 1.0 m\n
\n\n B. 2.0 m\n
\n\n C. 3.0 m\n
\n\n D. 4.9 m\n
\n\n [1]\n
\n\n C\n
\n\n The correct response, option C was the most popular chosen at HL but at SL significantly more candidates chose options A or B. The difficulty index of 21 and discrimination index of 0.27 at SL indicates that students found the question to be hard with lower discrimination between stronger and weaker candidates. It is felt that those who chose option A did not realise the block was accelerating down the slope, whereas those choosing B did but were unable to calculate the acceleration correctly.\n
\n\n A disc of mass\n \n M\n \n and radius\n \n R\n \n is on a horizontal frictionless table. Two equal and opposite forces, each of magnitude\n \n F\n \n , act on the disc. The moment of inertia of the disc about its axis is\n \n .\n
\n\n \n
\n What is the angular acceleration of the disc?\n
\n\n
\n A. 0\n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n \n Show that the value of\n \n \n \n \n \n is about 0.03.\n \n
\n\n [2]\n
\n\n \n gradient\n \n «\n \n »\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n use of equation with coordinates of a point\n \n \n ✓\n \n
\n \n
\n \n \n \n ✓\n \n
\n
\n\n \n \n MP1 allow gradients in range\n \n to\n \n
\n \n \n
\n \n \n MP2 allow a range\n \n to\n \n for\n \n \n \n \n \n
\n\n
\n\n Very well answered either by obtaining the gradient or replacing with the coordinates of a point.\n
\n\n Show that the current in Q is 0.45 A.\n
\n\n [3]\n
\n\n Voltage across P is 1.4 «V» ✓\n
\n\n Voltage across Q is 4.6 «V» ✓\n
\n\n And 6 – 1.4 = 4.6 «V» ✓\n
\n\n
\n\n \n Need to see a calculation involving the two voltages and the total voltage in the circuit for\n \n MP3\n \n (e.g. 1.4 + 4.6 = 6).\n \n
\n\n Deduce, with reference to entropy, that the expansion of the gas from the initial configuration A is irreversible.\n
\n\n [3]\n
\n\n The entropy of the gas is related to the number of microstates\n
\n\n \n OR\n \n
\n\n \n and\n \n ✓\n
\n\n
\n Since\n \n , the entropy in configuration B is greater ✓\n
\n A process that results in an increase of entropy in an isolated system is irreversible ✓\n
\n\n A spherical planet has a radius\n \n R\n \n \n 0\n \n .\n
\n\n The graph shows the variation of the gravitational potential due to the planet with distance\n \n r\n \n from the centre of the planet.\n
\n\n \n
\n What is the escape speed from the surface of the planet?\n
\n\n
\n A. 1.6 × 10\n \n 3\n \n m s\n \n −1\n \n
\n B. 2.2 × 10\n \n 3\n \n m s\n \n −1\n \n
\n\n C. 3.2 × 10\n \n 3\n \n m s\n \n −1\n \n
\n\n D. 4.5 × 10\n \n 3\n \n m s\n \n −1\n \n
\n\n [1]\n
\n\n C\n
\n\n \n does support the photon nature of light.\n \n
\n\n [2]\n
\n\n \n «in the photon theory of light» the electron interacts with a single photon ✔\n
\n and absorbs all the energy\n \n \n OR\n \n \n and can leave the metal immediately ✔\n
\n \n
\n \n \n NOTE: Reference to photon-electron collision scores MP1\n \n \n
\n\n Show that the electric charge on the oil drop is given by\n
\n\n \n
\n\n where\n \n is the density of oil and\n \n is the volume of the oil drop.\n
\n\n [2]\n
\n\n Mass of drop is\n \n ✓\n
\n\n \n ✓\n
\n\n «hence answer»\n
\n\n
\n \n MP1 must be shown implicitly for credit.\n \n
\n \n The student hypothesizes that the relationship between\n \n T\n \n and\n \n v\n \n is\n \n T = a + bv\n \n \n 2\n \n , where\n \n a\n \n and\n \n b\n \n are constants. To verify this hypothesis a graph showing the variation of\n \n T\n \n with\n \n v\n \n \n 2\n \n is plotted. The graph shows the data and the line of best fit.\n \n
\n\n \n \n \n
\n \n \n Determine\n \n b\n \n , giving an appropriate unit for\n \n b\n \n .\n \n \n
\n\n [3]\n
\n\n use of 2 correct points on the line with Δ\n \n v\n \n \n 2\n \n > 2 ✔\n
\n\n \n b\n \n in range 0.012 to 0.013 ✔\n
\n\n s\n \n 3\n \n m\n \n –2\n \n ✔\n
\n\n \n A train approaches a station and sounds a horn of constant frequency and constant intensity. An observer waiting at the station detects a frequency\n \n f\n \n \n obs\n \n and an intensity\n \n I\n \n \n obs\n \n . What are the changes, if any, in\n \n I\n \n \n obs\n \n and\n \n f\n \n \n obs\n \n as the train slows down?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n An unusual way of considering the Doppler effect, this had a very low discrimination index with the most popular answer A when D was correct. It is likely the candidates have confused what the train is producing – a constant intensity sound – and what the observer hears, Io, where the intensity is going to increase as the train approaches. This immediately eliminates options A and C.\n
\n\n A container holds a mixture of argon and helium atoms at a temperature of 37 °C.\n
\n\n Calculate the average translational speed of the argon atoms.\n
\n\n The molar mass of argon is 4.0 × 10\n \n −2\n \n kg mol\n \n −1\n \n .\n
\n\n [4]\n
\n\n Use of\n \n ✓\n
\n\n Work showing that\n \n ✓\n
\n\n Correct substitution AND conversion to K (310 K) ✓\n
\n\n 430/440 «m s\n \n −1\n \n » ✓\n
\n\n Monochromatic light of wavelength\n \n passes through a single-slit of width\n \n and produces a diffraction pattern on a screen. Which combination of changes to\n \n and\n \n will cause the greatest decrease in the width of the central maximum?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n Light of frequency\n \n is incident on a metallic surface of work function\n \n W\n \n . Photoelectrons with a maximum kinetic energy\n \n E\n \n \n max\n \n are emitted. The frequency of the incident light is changed to 2\n \n .\n
\n\n What is true about the maximum kinetic energy and the work function?\n
\n\n
\n| \n | \n\n \n Maximum kinetic energy\n \n | \n\n \n Work function\n \n | \n
| \n A.\n | \n\n less than 2\n \n E\n \n \n max\n \n | \n\n unchanged\n | \n
| \n B.\n | \n\n less than 2\n \n E\n \n \n max\n \n | \n\n greater than\n \n W\n \n | \n
| \n C.\n | \n\n greater than 2\n \n E\n \n \n max\n \n | \n\n unchanged\n | \n
| \n D.\n | \n\n greater than 2\n \n E\n \n \n max\n \n | \n\n greater than\n \n W\n \n | \n
\n [1]\n
\n\n C\n
\n\n Explain why the magnitude of the emf is related to the amplitude of the ground movement.\n
\n\n [3]\n
\n\n The springs have a natural time period for the oscillation ✓\n
\n\n A greater amplitude of movement leads to higher magnet speed (with constant time period) ✓\n
\n\n So field lines cut coil more quickly leading to greater emf ✓\n
\n\n On the diagram draw an arrow to show the direction of the magnetic field at Q due to wire X\n \n alone\n \n .\n
\n\n [1]\n
\n\n
\n\n \n
\n arrow of any length as shown ✓\n
\n\n in its initial circular orbit;\n
\n\n [1]\n
\n\n Negative ✓\n
\n\n The string is made to vibrate in its third harmonic. State the distance between consecutive nodes.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n Show that the speed of the wave on the string is about 240 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Answer must be to 3 or more sf\n \n or\n \n working shown for\n \n MP2.\n \n \n
\n\n The diagram shows field lines for an electrostatic field. X and Y are two points on the same field line.\n
\n\n \n
\n Outline which of the two points has the larger electric potential.\n
\n\n [2]\n
\n\n potential greater at Y ✓\n
\n\n
\n\n «from\n \n » the potential increases in the direction opposite to field strength «so from X to Y»\n
\n\n \n \n OR\n \n \n
\n\n opposite to the direction of the field lines, «so from X to Y»\n
\n\n \n \n OR\n \n \n
\n\n «from\n \n » work done to move a positive charge from X to Y is positive «so the potential increases from X to Y» ✓\n
\n\n A significant majority guessed at X, probably because the field lines are closer together. Those that identified Y were generally successful in their explanation.\n
\n\n A conducting ring encloses an area of 2.0 cm\n \n 2\n \n and is perpendicular to a magnetic field of strength 5.0 mT. The direction of the magnetic field is reversed in a time 4.0 s. What is the average emf induced in the ring?\n
\n\n A. 0\n
\n\n B. 0.25 μV\n
\n\n C. 0.40 μV\n
\n\n D. 0.50 μV\n
\n\n [1]\n
\n\n D\n
\n\n \n A radioactive nuclide with atomic number\n \n Z\n \n undergoes a process of beta-plus (β\n \n +\n \n ) decay. What is the atomic number for the nuclide produced and what is another particle emitted during the decay?\n \n
\n\n \n \n \n
\n [1]\n
\n\n A\n
\n\n The speed of sound in air is 340 m s\n \n −1\n \n and in water it is 1500 m s\n \n −1\n \n .\n
\n\n Discuss whether the sound wave can enter the water.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n critical angle\n \n «from\n \n » ✓\n
\n\n the angle of incidence is greater than\n \n hence the sound can’t enter water ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n ✓\n
\n\n sine value greater than one hence the sound can’t enter water ✓\n
\n\n
\n\n \n Conclusion must be justified, award\n \n [0]\n \n for\n \n BCA\n \n .\n \n
\n\n Surprisingly well answered as it was sound from air to water, rather than light from air to glass. A mixture of approaches but probably the most common was to calculate a sine value of over 1. Some went about calculating the critical angle but nowhere near as many.\n
\n\n Two of the brightest objects in the night sky seen from Earth are the planet Venus and the star Sirius. Explain why the equation\n \n is applicable to Sirius but not to Venus.\n
\n\n [2]\n
\n\n \n equation applies to Sirius/stars that are luminous/emit light «from fusion»\n \n \n ✓\n \n
\n\n \n but Venus reflects the Sun’s light/does not emit light\n \n \n «\n \n \n from fusion\n \n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n The magnitude of the resultant of two forces acting on a body is 12 N. Which pair of forces acting on the body can combine to produce this resultant?\n
\n\n A. 1 N and 2 N\n
\n\n B. 1 N and 14 N\n
\n\n C. 5 N and 6 N\n
\n\n D. 6 N and 7 N\n
\n\n [1]\n
\n\n D\n
\n\n This question was well answered by HL and SL candidates. There was a higher number of blanks (no response) among SL students than is typical this early in the exam paper.\n
\n\n A net force of 8.0 N accelerates a 4.0 kg body from rest to a speed of 5.0 m s\n \n −1\n \n .\n
\n\n What is the work done by the force?\n
\n\n
\n A. 50 J\n
\n B. 40 J\n
\n\n C. 32 J\n
\n\n D. 20 J\n
\n\n [1]\n
\n\n A\n
\n\n The air is a mixture of nitrogen, oxygen and other gases. Explain why the component gases of air in the container have different average translational speeds.\n
\n\n [3]\n
\n\n Average kinetic energy of the molecules is determined by the temperature only ✓\n
\n\n The mass of a molecule is different for each component gas ✓\n
\n\n From\n \n , the same\n \n and different mass implies a different average velocity ✓\n
\n\n determine the tension in the string.\n
\n\n [2]\n
\n\n \n T − mg = F\n \n net\n \n \n OR\n \n \n \n T − mg =\n \n \n ✓\n
\n\n \n T\n \n «= 0.800 × 9.81 +\n \n » = 23.5 «N» ✓\n
\n\n \n Show that the intensity radiated by the oceans is about 400 W m\n \n -2\n \n .\n \n
\n\n [1]\n
\n\n 5.67\n \n ×\n \n 10\n \n \n −8\n \n \n ×\n \n 289\n \n 4\n \n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n = 396 «W m\n \n −2\n \n » ✔\n \n
\n\n \n \n «≈ 400 W m\n \n \n −2\n \n \n »\n \n \n
\n\n
\n\n This was well answered with candidates scoring the mark for either a correct substitution or an answer given to at least one more sf than the show that value. Some candidates used 298 rather than 289.\n
\n\n Determine which star will appear to move more.\n
\n\n [2]\n
\n\n Star Y ✓\n
\n\n because parallax angle is greater\n \n \n OR\n \n \n star Y is closer «and that means movement relative to distant stars is greater» ✓\n
\n\n
\n\n \n Allow reverse argument for star X\n \n
\n\n An object of mass\n \n M\n \n is accelerated vertically upwards by a motor at a constant acceleration.\n
\n The object is initially at rest and reaches a vertical speed of 4.0 m s\n \n −1\n \n in 2.0 s.\n
\n \n
\n What is the average power output of the motor?\n
\n\n
\n A. 8\n \n M\n \n
\n B. 24\n \n M\n \n
\n\n C. 32\n \n M\n \n
\n\n D. 48\n \n M\n \n
\n\n [1]\n
\n\n B\n
\n\n A black body is on the Moon’s surface at point A. Show that the maximum temperature that this body can reach is 400 K. Assume that the Earth and the Moon are the same distance from the Sun.\n
\n\n [2]\n
\n\n \n T\n \n =\n \n \n \n \n \n ✔\n
\n\n 390 «K» ✔\n
\n\n \n Must see 1360 (from data booklet) used for MP1.\n \n
\n\n \n Must see at least 2 s.f\n \n .\n
\n\n Many candidates struggled with this question. A significant portion attempted to apply Wein’s Law and simply stated that a particular wavelength was the peak and then used that to determine the temperature. Some did use the solar constant from the data booklet and were able to calculate the correct temperature. As part of their preparation for the exam candidates should thoroughly review the data booklet and be aware of what constants are given there. As with all “show that” questions candidates should be reminded to include an unrounded answer.\n
\n\n The angle\n \n θ\n \n between a ramp and a horizontal surface slowly increases from zero. An object on the ramp does not slide as\n \n θ\n \n increases.\n
\n\n \n
\n The frictional force on the object is\n
\n\n
\n A. constant.\n
\n B. negligible.\n
\n\n C. proportional to cos\n \n θ\n \n .\n
\n\n D. proportional to sin\n \n θ\n \n .\n
\n\n [1]\n
\n\n D\n
\n\n outline the magnetic force acting on it due to the current in PQ.\n
\n\n [1]\n
\n\n «The force is» away from PQ/repulsive/to the right ✓\n
\n\n \n A particle of mass 0.02 kg moves in a horizontal circle of diameter 1 m with an angular velocity of 3\n \n \n \n rad s\n \n -1\n \n .\n
\n \n
\n \n What is the magnitude and direction of the force responsible for this motion?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n A block moving with initial speed\n \n \n \n is brought to rest, after travelling a distance\n \n d\n \n , by a frictional force\n \n \n \n . A second identical block moving with initial speed\n \n u\n \n is brought to rest in the same distance\n \n d\n \n by a frictional force\n \n . What is\n \n u\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n With a lower difficulty index for SL candidates than for HL candidates, this question asked students to recognize the relationship between variables in a kinematics equation. For both groups, option C (incorrect) was most frequently selected, as candidates struggled to show the relationship between U and the change in frictional force. This question would be a useful teaching tool, as results here suggest candidates should spend more time working with equations without numerical substitutions.\n
\n\n Outline why the cylinder performs simple harmonic motion when released.\n
\n\n [1]\n
\n\n \n the\n \n \n «\n \n \n restoring\n \n \n »\n \n \n force/acceleration is proportional to displacement\n \n \n ✓\n \n
\n\n \n \n
\n Allow use of symbols i.e.\n \n \n \n or\n \n \n \n
\n This was well answered with candidates gaining credit for answers in words or symbols.\n
\n\n \n Monochromatic light is used to produce double-slit interference fringes on a screen. The fringe separation on the screen is\n \n . The distance from the slits to the screen and the separation of the slits are both doubled, and the light source is unchanged. What is the new fringe separation on the screen?\n \n
\n\n \n A.\n \n \n
\n\n B.\n \n \n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The graph shows the variation of the gravitational potential between the Earth and Moon with distance from the centre of the Earth. The distance from the Earth is expressed as a fraction of the total distance between the centre of the Earth and the centre of the Moon.\n
\n\n \n
\n Determine, using the graph, the mass of the Moon.\n
\n\n [3]\n
\n\n read off separation at maximum potential 0.9 ✔\n
\n\n equating of gravitational field strength of earth and moon at that location\n \n \n OR\n \n ✔\n \n \n
\n 7.4 × 10\n \n 22\n \n «kg» ✔\n
\n\n \n Allow ECF from MP1\n \n
\n\n This question was left blank by many candidates, and very few who attempted it were able to successfully recognize that the gravitational fields of the Earth and Moon balance at 0.9r and then use the proper equation to calculate the mass of the Moon.\n
\n\n Determine the velocity of the first curling stone.\n
\n\n [2]\n
\n\n 2.04 m s\n \n −1\n \n ✓\n
\n\n At 7.9° to initial direction ✓\n
\n\n Conductor X is connected to a cell of emf\n \n E\n \n . A power of 16 W is dissipated in X.\n
\n\n Conductor Y is made from the same material with the same diameter as X but is twice as long. A cell of emf 2\n \n E\n \n is connected to Y.\n
\n\n Both cells have negligible internal resistance.\n
\n\n What power is dissipated in Y?\n
\n\n \n
\n
\n A. 8.0 W\n
\n B. 16 W\n
\n\n C. 32 W\n
\n\n D. 64 W\n
\n\n [1]\n
\n\n C\n
\n\n Show that\n \n .\n
\n\n [2]\n
\n\n Equates centripetal force (with Newton’s law of gravitation\n \n )\n
\n\n \n \n OR\n \n \n
\n\n \n ✓\n
\n\n
\n Uses both equation correctly with clear re-arrangement ✓\n
\n \n Radioactive decay is said to be “random” and “spontaneous”. Outline what is meant by each of these terms.\n \n
\n\n \n Random:\n \n
\n\n \n Spontaneous:\n \n
\n\n [2]\n
\n\n \n \n random:\n \n
\n it cannot be predicted which nucleus will decay\n
\n \n \n OR\n \n \n
\n it cannot be predicted when a nucleus will decay ✔\n
\n \n
\n \n \n NOTE: OWTTE\n \n
\n \n
\n
\n\n \n \n spontaneous:\n \n
\n the decay cannot be influenced/modified in any way ✔\n
\n \n
\n \n \n NOTE:\n \n \n OWTTE\n \n
\n \n
\n The maximum height reached by the bottle is greater with an air–water mixture than with only high-pressure air in the bottle.\n
\n\n Assume that the speed at which the propellant leaves the bottle is the same in both cases.\n
\n\n Explain why the bottle reaches a greater maximum height with an air–water mixture.\n
\n\n [2]\n
\n\n Mass «leaving the bottle per second» will be larger for air–water ✓\n
\n\n the momentum change/force is greater ✓\n
\n\n
\n\n \n Allow opposite argument for air only\n \n
\n\n \n Explain why some of this radiation is returned to the oceans from the atmosphere.\n \n
\n\n [3]\n
\n\n \n «most of the radiation emitted by the oceans is in the» infrared ✔\n
\n \n
\n \n «this radiation is» absorbed by greenhouse gases/named greenhouse gas in the atmosphere ✔\n
\n \n
\n \n «the gases» reradiate/re-emit ✔\n
\n \n
\n \n partly back towards oceans/in all directions/awareness that radiation in other directions is also present ✔\n \n
\n\n For many this was a well-rehearsed answer which succinctly scored full marks. For others too many vague terms were used. There was much talk about energy being trapped or reflected and the ozone layer was often included. The word ‘albedo’ was often written down with no indication of what it means and ‘the albedo effect also featured.\n
\n\n orbital speed;\n
\n\n [1]\n
\n\n «\n \n »\n \n «m s\n \n −1\n \n » ✓\n
\n\n A planet has radius\n \n R\n \n . The escape speed from the surface of the planet is\n \n v\n \n . At what distance from the surface of the planet is the orbital speed 0.5\n \n v\n \n ?\n
\n\n A. 0.5\n \n R\n \n
\n\n B.\n \n R\n \n
\n\n C. 2\n \n R\n \n
\n\n D. 4\n \n R\n \n
\n\n [1]\n
\n\n B\n
\n\n \n The student models the bounce of the tennis ball to predict the angle\n \n θ\n \n at which the ball leaves a surface of clay and a surface of grass.\n \n
\n\n \n \n \n
\n \n \n The model assumes\n
\n \n \n
\n \n \n • during contact with the surface the ball slides.\n
\n • the sliding time is the same for both surfaces.\n
\n • the sliding frictional force is greater for clay than grass.\n
\n • the normal reaction force is the same for both surfaces.\n
\n \n \n
\n \n \n Predict for the student’s model, without calculation, whether θ is greater for a clay surface or for a grass surface.\n \n \n
\n\n [3]\n
\n\n \n so horizontal velocity component at lift off for clay is smaller ✔\n
\n \n
\n \n normal force is the same so vertical component of velocity is the same ✔\n
\n \n
\n \n so bounce angle on clay is greater ✔\n \n \n \n
\n \n \n
\n As the command term in this question is ‘predict’ a bald answer of clay was acceptable for one mark. This was a testing question that candidates found demanding but there were some very well-reasoned answers. The most common incorrect answer involved suggesting that the greater frictional force on the clay court left the ball with less kinetic energy and so a smaller angle. At SL many gained the answer that the angle on clay would be greater with the argument that frictional force is greater and so the distance the ball slides is less.\n
\n\n A vessel contains a mass\n \n X\n \n of helium gas and a mass 2\n \n X\n \n of oxygen gas.\n
\n\n Molar mass of helium = 4 g\n
\n\n Molar mass of oxygen = 32 g\n
\n\n What is the\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 4\n
\n\n D. 8\n
\n\n [1]\n
\n\n C\n
\n\n The smallest mass of magnesium that can be detected with this technique is 1.1 × 10\n \n −8\n \n kg.\n
\n\n Show that the smallest number of magnesium atoms that can be detected with this technique is about 10\n \n 17\n \n .\n
\n\n [2]\n
\n\n So 1.1 × 10\n \n −8\n \n kg ≡\n \n × 10\n \n −8\n \n «mol»\n
\n\n \n \n OR\n \n \n
\n\n Mass of atom = 27 × 1.66 × 10\n \n −27\n \n «kg» ✓\n
\n\n 2.4 − 2.5 x 10\n \n 17\n \n atoms ✓\n
\n\n State what will happen to the width of the primary maxima.\n
\n\n [1]\n
\n\n decreases ✓\n
\n\n Resistor P is removed. State and explain, without any calculations, the effect of this on the resistance of Q.\n
\n\n [2]\n
\n\n Q will have a smaller resistance ✓\n
\n\n «Because total resistance in the circuit is now larger so» the current «through the\n
\n circuit/Q» is smaller /\n \n \n OWTTE\n \n \n ✓\n \n \n
\n \n \n
\n \n Allow similar argument for\n \n MP2\n \n based on voltage across\n \n Q\n \n becoming smaller.\n \n
\n\n Determine the minimum energy required to launch the satellite. Ignore the original kinetic energy of the satellite due to Earth’s rotation.\n
\n\n [2]\n
\n\n change in PE\n \n «\n \n J» ✓\n
\n\n energy needed = KE + ΔPE =\n \n «J» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from 8(b)(i).\n \n
\n\n Generally, this question was not well done. Most carried out a calculation based on the formula for escape velocity. An opportunity to remind candidates of reading back the stem for the sub-question when answering a second or any subsequent part of it.\n
\n\n Draw, on the axes, a graph to show the variation with\n \n t\n \n of the displacement of particle Q.\n
\n\n [2]\n
\n\n oscillation in antiphase ✓\n
\n\n smaller amplitude than P ✓\n
\n\n
\n \n
\n Although there were good answers which scored full marks, there were a significant number of wrong answers where the amplitude was the same or not consistent throughout, or the wave drawn was not in antiphase of the original sketch.\n
\n\n A model rocket is launched from rest. The graph shows the variation with time\n \n t\n \n of the net force\n \n F\n \n applied on the rocket. The average mass of the rocket is 0.20 kg.\n
\n\n \n
\n What is the maximum velocity reached by the rocket?\n
\n\n
\n A. 3.0 m s\n \n −1\n \n
\n B. 25 m s\n \n −1\n \n
\n\n C. 75 m s\n \n −1\n \n
\n\n D. 150 m s\n \n −1\n \n
\n\n [1]\n
\n\n C\n
\n\n The energy of the\n \n n\n \n th level of hydrogen is given by\n \n . What is the frequency of the photon emitted in the transition from\n \n to\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n A black body is on the Moon’s surface at point A. Show that the maximum temperature that this body can reach is 400 K. Assume that the Earth and the Moon are the same distance from the Sun.\n
\n\n [2]\n
\n\n \n T\n \n =\n \n \n \n \n \n ✔\n
\n\n 390 «K» ✔\n
\n\n \n Must see 1360 (from data booklet) used for MP1.\n \n
\n\n \n Must see at least 2 s.f\n \n .\n
\n\n Many candidates struggled with this question. A significant portion attempted to apply Wein’s Law and simply stated that a particular wavelength was the peak and then used that to determine the temperature. Some did use the solar constant from the data booklet and were able to calculate the correct temperature. As part of their preparation for the exam candidates should thoroughly review the data booklet and be aware of what constants are given there. As with all “show that” questions candidates should be reminded to include an unrounded answer.\n
\n\n A mass is released from the top of a smooth ramp of height\n \n \n \n . After leaving the ramp, the mass slides on a rough horizontal surface.\n
\n\n \n
\n The mass comes to rest in a distance\n \n d\n \n . What is the coefficient of dynamic friction between the mass and the horizontal surface?\n
\n\n \n
\n\n \n
\n\n \n
\n\n \n
\n\n [1]\n
\n\n D\n
\n\n Outline why electrons with energy of approximately\n \n would be unsuitable for the investigation of nuclear radii.\n
\n\n [2]\n
\n\n \n the de Broglie wavelength of electrons is\n \n \n «\n \n \n much\n \n \n »\n \n \n longer than the size of a nucleus\n \n \n ✓\n \n
\n\n \n
\n \n \n hence electrons would not undergo diffraction\n
\n \n \n \n \n OR\n \n \n
\n \n \n no diffraction pattern would be observed\n \n \n ✓\n \n
\n Candidates generally scored poorly on this question. There was confusion between this experiment and another diffraction one, so often the new wavelength was compared to the spacing between atoms. Also, in line with answers to b(i) there were suggestions that the electrons did not have sufficient energy to reach the nucleus or would be deflected by too great an angle to be seen.\n
\n\n A working refrigerator with the door open is placed in a sealed room.\n
\n\n The entropy of the room\n
\n\n
\n A. is zero.\n
\n B. decreases.\n
\n\n C. remains unchanged.\n
\n\n D. increases.\n
\n\n [1]\n
\n\n D\n
\n\n There are eight wheels on each tram with a brake system for each wheel. A pair of brake pads clamp firmly onto an annulus made of steel.\n
\n\n The train comes to rest from speed\n \n v\n \n . Ignore the energy transferred to the brake pads and the change in the gravitational potential energy of the tram during the braking.\n
\n\n Calculate the temperature change in each steel annulus as the tram comes to rest.\n
\n\n Data for this question\n
\n\n The inner radius of the annulus is 0.40 m and the outer radius is 0.50 m.\n
\n\n The thickness of the annulus is 25 mm.\n
\n\n The density of the steel is 7860 kg m\n \n −3\n \n
\n\n The specific heat capacity of the steel is 420 J kg\n \n −1\n \n K\n \n −1\n \n
\n\n [4]\n
\n\n Work leading to volume = 7.1 x 10\n \n −3\n \n m\n \n 3\n \n ✓\n
\n\n Work leading to mass of steel = 55 .8 kg ✓\n
\n\n Kinetic Energy transferred per annulus =\n \n
\n\n = 110 kJ ✓\n
\n\n \n K ✓\n
\n\n White dwarfs with similar volumes to each other are shown on the HR diagram.\n
\n\n Sketch, on the HR diagram, to show the possible positions of other white dwarf stars with similar volumes to those marked on the HR diagram.\n
\n\n [2]\n
\n\n Any evidence of correct identification that three dots bottom left represent white dwarfs ✓\n
\n\n line passing through all 3 white dwarfs\n \n \n OR\n \n \n line continuing from 3 white dwarfs with approximately same gradient, in either direction ✓\n
\n\n
\n\n \n Award\n \n MP2\n \n if no line drawn through the three dots but just beyond them in either direction\n \n
\n\n Player B intercepts the ball when it is at its peak height. Player B holds a paddle (racket) stationary and vertical. The ball is in contact with the paddle for 0.010 s. Assume the collision is elastic.\n
\n\n \n
\n Calculate the average force exerted by the ball on the paddle. State your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n \n «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n 5.67 «N»\n \n ✓\n \n
\n\n any answer to 2 significant figures «N»\n \n ✓\n \n
\n\n The package and string are now released and fall to the ground. The lift force on the aircraft remains unchanged. Calculate the initial acceleration of the aircraft.\n
\n\n [2]\n
\n\n \n vertical force = lift force – weight\n \n \n \n \n OR\n \n \n \n \n \n OR\n \n \n \n \n \n ✓\n \n
\n\n \n acceleration\n \n \n \n ✓\n \n
\n\n Calculate, using the answers to (b)(i) and (b)(ii) the ratio\n \n in S.\n
\n\n [2]\n
\n\n transit time is one half life ✓\n
\n\n so ratio has to be\n \n ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n .\n \n
\n\n What is the sequence for the evolution of a main sequence star of about 2 solar masses?\n
\n\n
\n A. Red super giant → supernova → neutron star\n
\n B. Red giant → planetary nebula → white dwarf\n
\n\n C. Red giant → supernova → white dwarf\n
\n\n D. Red super giant → planetary nebula → neutron star\n
\n\n [1]\n
\n\n B\n
\n\n magnitude of the net force acting on the loop;\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «N» ✓\n
\n\n The orbital radius of Titan around Saturn is 1.2 × 10\n \n 9\n \n m and the orbital period is 15.9 days. Estimate the mass of Saturn.\n
\n\n [2]\n
\n\n \n «s» ✓\n
\n\n \n «kg» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n State what is meant by the Doppler effect.\n
\n\n [2]\n
\n\n the change in the observed frequency ✓\n
\n\n when there is relative motion between the source and the observer ✓\n
\n\n
\n\n \n Do not award\n \n MP1\n \n if they refer to wavelength.\n \n
\n\n \n Calculate the time for\n \n one\n \n complete revolution.\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n \n \n « s » ✔\n \n
\n\n \n \n NOTE: Award\n \n [2]\n \n for bald correct answer\n \n \n
\n\n White light is emitted from a hot filament. The light passes through hydrogen gas at low pressure and then through a diffraction grating onto a screen. A pattern of lines against a background appears on the screen.\n
\n\n \n
\n What is the appearance of the lines and background on the screen?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n An energy of 200 J is transferred isothermally to an ideal gas. The temperature of the gas is 27 °C.\n
\n\n The entropy change of the gas is\n
\n\n
\n A. 0.67 J K\n \n −1\n \n
\n B. 0.14 J K\n \n −1\n \n
\n\n C. 1.5 J K\n \n −1\n \n
\n\n D. 7.4 J K\n \n −1\n \n
\n\n [1]\n
\n\n A\n
\n\n \n A table-tennis ball of mass 3 g is fired with a speed of 10 m s\n \n -1\n \n from a stationary toy gun of mass 0.600 kg. The gun and ball are an isolated system.\n
\n \n
\n \n What are the recoil speed of the toy gun and the total momentum of the system immediately after the gun is fired?\n \n
\n\n \n \n \n
\n [1]\n
\n\n A\n
\n\n This question gives good discrimination at both levels with the correct response, A, being the most popular at HL. Response B was second most popular at HL and most popular by a small margin at SL, however a significant number of candidates chose the other responses at both levels. Realising the gun and ball are initially at rest and momentum must be conserved leads to a zero momentum after firing, immediately removing options B and D.\n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n State the phase difference between the waves at V and Y.\n
\n\n [1]\n
\n\n 0\n \n \n OR\n \n \n 2\n \n π\n \n \n \n OR\n \n \n 360°\n \n ✓\n \n
\n\n
\n\n State the nature and direction of the force that accelerates the 15 kg object.\n
\n\n [1]\n
\n\n static friction force «between blocks»\n
\n\n \n \n AND\n \n \n
\n\n directed to the right ✓\n
\n\n A spacecraft, moving with speed\n \n v\n \n relative to Earth, passes Earth on its way to a planet. As the spacecraft passes Earth, clocks on Earth and in the spacecraft show zero.\n
\n\n The planet is a distance\n \n D\n \n from Earth, according to an observer on Earth.\n
\n\n What are the readings on the Earth clock and on the spacecraft clock when the spacecraft arrives at the planet?\n
\n
\n
\n \n
\n [1]\n
\n\n A\n
\n\n The points X and Y are in a uniform electric field of strength\n \n . The distance OX is\n \n and the distance OY is\n \n .\n
\n\n \n
\n What is the magnitude of the change in electric potential between X and Y?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n \n determine the thermal energy removed from the system.\n \n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n work done\n \n \n ✔\n \n
\n\n change in internal energy\n \n
\n \n \n OR\n
\n \n \n \n \n \n \n \n \n ✔\n \n
\n thermal energy removed\n \n
\n \n \n OR\n
\n \n \n \n \n \n \n \n \n ✔\n \n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n \n ✔\n \n
\n\n thermal energy removed\n \n \n ✔\n \n
\n\n \n \n \n \n ✔\n \n
\n\n \n Show that the tennis ball passes over the net.\n \n
\n\n [3]\n
\n\n \n \n \n ALTERNATIVE 1\n \n
\n \n \n
\n \n \n u\n \n y\n \n \n \n \n = 64\n \n \n sin7\n \n \n /7.80\n \n \n \n «\n \n \n \n ms\n \n \n \n \n −\n \n \n \n 1\n \n \n \n \n »\n \n \n \n ✔\n \n \n \n
\n \n \n
\n \n decrease in height = 7.80\n \n ×\n \n 0.187 +\n \n \n \n \n ×\n \n 9.81\n \n ×\n \n 0.187\n \n 2\n \n /1.63 «m» ✔\n
\n \n
\n \n final height = «\n \n 2.80 − 1.63\n \n » = 1.1/1.2 «m» ✔\n
\n \n
\n \n «higher than net so goes over»\n
\n \n
\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n
\n \n vertical distance to fall to net\n \n «\n \n =\n \n 2.80 − 0.91\n \n » = 1.89 «m»✔\n
\n \n
\n \n time to fall this distance found using\n \n «\n \n =1.89 = 7.8\n \n t\n \n +\n \n \n \n \n \n \n ×\n \n 9.81\n \n ×\n \n \n t\n \n \n 2\n \n »\n
\n \n
\n \n \n t\n \n = 0.21 «s»✔\n
\n \n
\n \n 0.21 «s» > 0.187 «s» ✔\n
\n \n
\n \n «reaches the net before it has fallen far enough so goes over»\n \n \n \n
\n \n \n
\n \n \n Other alternatives are possible\n
\n \n \n
\n There were a number of approaches students could take to answer this and examiners saw examples of them all. One approach taken was to calculate the time taken to fall the distance to the top of the net and to compare this with the time calculated in bi) for the ball to reach the net. This approach, which is shown in the mark scheme, required solving a quadratic in t which is beyond the mathematical requirements of the syllabus. This mathematical technique was only required if using this approach and not required if, for example, calculating heights.\n
\n\n A common mistake was to forget that the ball has a vertical acceleration. Examiners were able to award credit/ECF for correct parts of an otherwise flawed method.\n
\n\n The system rotates from rest and reaches a maximum angular speed of 20 rad s\n \n −1\n \n in a time of 5.0 s. Calculate the angular acceleration of the system.\n
\n\n [1]\n
\n\n «α =\n \n =» 4 «rad s\n \n −2\n \n » ✓\n
\n\n Two spaceships, X and Y move in opposite directions away from a space station. The speeds of the spaceships relative to the space station are\n \n \n \n and\n \n \n \n .\n
\n\n \n
\n What is the speed of Y in the reference frame of X?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n A block rests on a frictionless horizontal surface. An air rifle pellet is fired horizontally into the block and remains embedded in the block.\n
\n\n \n
\n What happens to the total kinetic energy and to the total momentum of the block and pellet system as a result of the collision?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n An object is released from rest in a vacuum at a height\n \n \n \n above the Earth’s surface.\n
\n\n As the object falls it passes a point at a height of 0.75\n \n \n \n above the surface.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The total friction in the system acting on the tram is equivalent to an opposing force of 750 N.\n
\n\n For one particular journey, the tram is full of passengers.\n
\n\n Estimate the maximum speed\n \n v\n \n of the tram as it leaves the lower station.\n
\n\n [4]\n
\n\n Total weight of tram = 75 × 710 + 5 × 10\n \n 4\n \n = 1.03 × 10\n \n 5\n \n N ✓\n
\n\n Total force down track = 750 + 1.03 × 10\n \n 5\n \n sin (10) = 1.87 × 10\n \n 4\n \n N ✓\n
\n\n Use of\n \n P\n \n =\n \n F ×\n \n \n v ✓\n \n
\n\n (\n \n v\n \n = 247 000 ÷ 1.87 × 10\n \n 4\n \n )= 13 m s\n \n −1\n \n ✓\n
\n\n Strontium-90 is a waste product from nuclear reactors that has a decay constant of 7.63 x 10\n \n −10\n \n s\n \n −1\n \n . Determine, in s, the time that it takes for the activity of strontium-90 to decay to 2% of its original activity.\n
\n\n [2]\n
\n\n \n or equivalent seen ✓\n
\n\n \n Gs ✓\n
\n\n A block is on the surface of a horizontal rotating disk. The block is at rest relative to the disk. The disk is rotating at constant angular velocity.\n
\n\n What is the correct arrow to represent the direction of the frictional force acting on the block at the instant shown?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n Candidate responses were largely divided between responses C and D, suggesting some confusion around the direction of frictional force in a rotating object (vs. linear motion).\n
\n\n The mixture was held in a large metal container during the mixing.\n
\n\n Explain\n \n one\n \n change to the procedure that will reduce the difference in (b)(i).\n
\n\n [1]\n
\n\n Insulate the container\n
\n\n \n OR\n \n
\n\n Carry out experiment quicker\n
\n\n \n OR\n \n
\n\n Use larger volumes of substances ✓\n
\n\n \n What is meant by the statement that the average albedo of the Moon is 0.1?\n \n
\n\n \n A. 10% of the radiation incident on the Moon is absorbed by its surface\n
\n \n
\n \n B. 10% of the radiation emitted by the Moon is absorbed by its atmosphere\n
\n \n
\n \n C. 10% of the radiation incident on the Moon is reflected by its surface\n
\n \n
\n \n D. 10% of the radiation emitted by the Moon is at infrared wavelengths\n \n
\n\n [1]\n
\n\n C\n
\n\n Two cells each of emf 9.0 V and internal resistance 3.0 Ω are connected in series. A 12.0 Ω resistor is connected in series to the cells. What is the current in the resistor?\n
\n\n A. 0.50 A\n
\n\n B. 0.75 A\n
\n\n C. 1.0 A\n
\n\n D. 1.5 A\n
\n\n [1]\n
\n\n C\n
\n\n This question was well answered by candidates and had a higher discrimination index.\n
\n\n \n Explain why the path of the proton is a circle.\n \n
\n\n [2]\n
\n\n \n magnetic force is to the left «at the instant shown»\n
\n \n \n OR\n \n \n
\n explains a rule to determine the direction of the magnetic force ✔\n \n
\n \n force is perpendicular to velocity/«direction of» motion\n
\n \n \n OR\n \n \n
\n force is constant in magnitude ✔\n \n
\n \n force is centripetal/towards the centre ✔\n \n
\n\n \n \n NOTE: Accept reference to acceleration instead of force\n \n \n
\n\n State the nucleon number of the He isotope that\n \n decays into.\n
\n\n [1]\n
\n\n 3 ✓\n
\n\n \n Do\n \n not\n \n accept\n \n by itself.\n \n
\n\n Two radioactive samples\n \n and\n \n have the same half-life. Initially the ratio\n \n is 4.\n
\n\n What is this ratio after 2 half-lives?\n
\n\n
\n A.\n \n
\n B. 1\n
\n\n C. 2\n
\n\n D. 4\n
\n\n [1]\n
\n\n D\n
\n\n Outline, using these two cases as examples, the distinction between a microstate and a macrostate.\n
\n\n [3]\n
\n\n Idea that a microstate is one (unique) arrangement of a system assuming that each entity in the system is distinguishable OWTTE ✓\n
\n\n Idea that a macrostate is an arrangement of microstates which have an identical outcome when individuals are not treated as distinguishable ✓\n
\n\n Suitable link to this example: e.g. there is only one arrangement (macrostate) in which there are 49 molecules in one container even though there are 50 (microstates or) ways to arrange this ✓\n
\n\n Outline why the results of the experiment are inconsistent with the wave model of electromagnetic radiation.\n
\n\n [2]\n
\n\n The wavelength of the X-rays changes ✓\n
\n\n According to the wave model, the wavelength of the incident and scattered X-rays should be the same ✓\n
\n\n The distance from S1 to Y is 1.243 m and the distance from S2 to Y is 1.181 m.\n
\n
\n Determine the frequency of the microwaves.\n
\n [3]\n
\n\n path difference = 0.062 «m» ✔\n
\n\n so wavelength = 0.031 «m» ✔\n
\n\n frequency = 9.7 × 10\n \n 9\n \n «Hz» ✔\n
\n\n \n If no unit is given, assume the answer is in Hz. Accept other prefixes (eg 9.7 GHz)\n \n
\n\n \n Award\n \n [2 max]\n \n for 4.8 x 10\n \n 9\n \n Hz.\n \n
\n\n Many candidates struggled with this question. Few were able to calculate a proper path length difference, and then use that to calculate the wavelength and frequency. Many candidates went down blind paths of trying various equations from the data booklet, and some seemed to believe that the wavelength is just the reciprocal of the frequency.\n
\n\n \n Outline why the normal force acting on the ladder at the point of contact with the wall is equal to the frictional force\n \n F\n \n between the ladder and the ground.\n \n
\n\n [1]\n
\n\n \n «translational equilibrium demands that the»\n \n \n resultant force in the horizontal direction must be zero✔\n
\n \n
\n \n «hence\n \n N\n \n \n W\n \n =\n \n F»\n \n \n
\n\n \n \n \n Equality of forces is given, look for reason why.\n \n \n \n
\n\n Many candidates stated that the resultant of all forces must be zero but failed to mention the fact that horizontal forces must balance in this particular question.\n
\n\n Draw the magnetic field lines due to A.\n
\n\n [2]\n
\n\n At least one circle centred on centre of wire A\n
\n \n \n AND\n
\n \n \n indication of clockwise direction ✓\n
\n More than 2 circles with increasing separation between circles from centre outwards (by eye) ✓\n
\n\n Show that the angular speed of the system immediately after the collision is about 5.7 rad s\n \n −1\n \n .\n
\n\n [2]\n
\n\n angular speed of particle = «12/0.6 = » 20 «rad s\n \n −1\n \n »\n
\n\n \n \n OR\n \n \n
\n\n angular momentum of particle «0.200 × 12.0 × 0.60» = 1.44 «Js» ✓\n
\n\n
\n «angular momentum of rod-particle system 0.252\n \n ω\n \n »\n
\n equating\n \n ω\n \n = «\n \n » = 5.71 rad s\n \n −1\n \n ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , working or answer to at least 3 SF should be seen.\n \n
\n\n State the range of current that the ammeter can measure as the slider S of the potential divider is moved from Q to P.\n
\n\n [1]\n
\n\n \n from\n \n to\n \n \n \n ✓\n \n
\n\n The unified atomic mass unit, u, is a non-SI unit usually used by scientists to state atomic masses.\n
\n\n What is u?\n
\n\n
\n A. It is the mean of the masses of a proton and a neutron.\n
\n B. It is the mean of the masses of protons and neutrons in all chemical elements.\n
\n\n C. It is\n \n the mass of an\n \n atom.\n
\n\n D. It is\n \n the mass of a\n \n atom.\n
\n\n [1]\n
\n\n D\n
\n\n In two different experiments, white light is passed through a single slit and then is either refracted through a prism or diffracted with a diffraction grating. The prism produces a band of colours from M to N. The diffraction grating produces a first order spectrum P to Q.\n
\n\n \n
\n What are the colours observed at M and P?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n This has low discrimination and the difficulty index suggests candidates found it hard with the incorrect option C being the most popular. The spreading of colours and formation of a spectrum (or rainbow) is something that is covered during an introductory course in physics and then developed in refraction and diffraction.\n
\n\n State the direction of the current in R, relative to the current in P.\n
\n\n [1]\n
\n\n Opposite ✓\n
\n\n The following data for the Mars–Phobos system and the Earth–Moon system are available:\n
\n\n Mass of Earth = 5.97 × 10\n \n 24\n \n kg\n
\n\n The Earth–Moon distance is 41 times the Mars–Phobos distance.\n
\n\n The orbital period of the Moon is 86 times the orbital period of Phobos.\n
\n\n Calculate, in kg, the mass of Mars.\n
\n\n [2]\n
\n\n \n \n \n \n \n or other consistent re-arrangement ✔\n
\n\n 6.4 × 10\n \n 23\n \n «kg» ✔\n
\n\n
\n\n This question was challenging for candidates. The candidates who started down the correct path of using the given derived value from 5bi often simply forgot that the multiplication factors had to be squared and cubed as well as the variables.\n
\n\n Titan has an atmosphere of nitrogen. The albedo of the atmosphere is 0.22. The surface of Titan may be assumed to be a black body. Explain why the\n \n average\n \n intensity of solar radiation\n \n absorbed\n \n by the whole surface of Titan is 3.1 W m\n \n −2\n \n
\n\n [3]\n
\n\n exposed surface is ¼ of the total surface ✓\n
\n\n absorbed intensity = (1−0.22) × incident intensity ✓\n
\n\n 0.78 × 0.25 × 15.7\n \n \n OR\n \n \n 3.07 «W m\n \n −2\n \n » ✓\n
\n\n
\n\n \n Allow 3.06 from rounding and 3.12 if they use 16\n \n W m\n \n −2\n \n .\n
\n\n Show, using the data, that the energy released in the decay of one magnesium-27 nucleus is about 2.62 MeV.\n
\n\n Mass of aluminium-27 atom = 26.98153 u\n
\n Mass of magnesium-27 atom = 26.98434 u\n
\n The unified atomic mass unit is 931.5 MeV c\n \n −2\n \n .\n
\n [1]\n
\n\n (26.98434 - 26.98153) × 931.5\n
\n\n \n \n OR\n \n \n
\n\n 2.6175 «MeV» seen ✓\n
\n\n \n A student blows across the top of a cylinder that contains water. A first-harmonic standing sound wave is produced in the air of the cylinder. More water is then added to the cylinder. The student blows so that a first-harmonic standing wave is produced with a different frequency.\n \n
\n\n \n \n \n
\n \n \n What is the nature of the displacement in the air at the water surface and the change in frequency when the water is added?\n \n \n
\n\n \n \n \n \n \n
\n [1]\n
\n\n D\n
\n\n Explain the variation in intensity.\n
\n\n [3]\n
\n\n «incident and reflected» waves superpose/interfere/combine ✓\n
\n\n «that leads to» standing waves formed\n \n \n OR\n \n \n nodes and antinodes present ✓\n
\n\n at antinodes / maxima there is maximum intensity / constructive interference / «displacement» addition / louder sound ✓\n
\n\n at nodes / minima there is minimum intensity / destructive interference / «displacement» cancellation / quieter sound ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n \n Allow a sketch of a standing wave for\n \n MP2\n \n \n
\n\n \n Allow a correct reference to path or phase differences to identify constructive / destructive interference\n \n
\n\n ai) On most occasions it looked like students knew more than they could successfully communicate. Lots of answers talked about interference between the 2 waves, or standing waves being produced but did not go on to add detail. Candidates should take note of how many marks the question part is worth and attempt a structure of the answer that accounts for that. At SL there were problems recognizing a standard question requiring the typical explanation of how a standing wave is established.\n
\n\n 3aii) By far the most common answer was 2800 Hz, not doubling the value given to get the correct wavelength. That might suggest that some students misinterpreted adjacent minima as two troughs, therefore missing to use the information to correctly determine the wavelength as 0.24 m.\n
\n\n b) A question that turned out to be a good high level discriminator. Most candidates went for an answer that generally had everything at a lower intensity and didn't pick up on the relative amount of superposition. Those that did answer it very well, with very clear explanations, succeeded in recognizing that the nodes would be louder and the anti-nodes would be quieter than before.\n
\n\n Calculate the fraction of the kinetic energy of the bottle that remains after the bounce.\n
\n\n [2]\n
\n\n Attempt to evaluate KE ratio as\n \n ✓\n
\n\n «\n \n =» 0.20\n \n \n OR\n \n \n 20 %\n \n \n OR\n \n \n \n ✓\n
\n\n
\n\n \n Accept ± 0.5 velocity values from graph\n \n
\n\n A mass on the end of a string is rotating on a frictionless table in circular motion of radius\n \n R\n \n \n 1\n \n and undergoes an angular displacement of\n \n θ\n \n in time\n \n t\n \n .\n
\n\n \n
\n The string tension is kept constant, but the angular displacement of the mass is increased to 2\n \n θ\n \n in time\n \n t\n \n . The radius of the motion changes to\n \n R\n \n \n 2\n \n .\n
\n\n What is\n \n R\n \n \n 2\n \n ?\n
\n\n
\n A.\n \n
\n B. 2\n \n R\n \n \n 1\n \n
\n\n C. 4\n \n R\n \n \n 1\n \n
\n\n D.\n \n R\n \n \n 1\n \n ×\n \n R\n \n \n 1\n \n
\n\n [1]\n
\n\n A\n
\n\n An asteroid (minor planet) orbits the Sun in a circular orbit of radius 4.5 × 10\n \n 8\n \n km. The radius of Earth’s orbit is 1.5 × 10\n \n 8\n \n km. Calculate, in years, the orbital period of the asteroid.\n
\n\n [2]\n
\n\n An attempt to use Kepler’s 3\n \n rd\n \n law, e.g.,\n \n ✓\n
\n\n \n «\n \n » 5.2 «years» ✓\n
\n\n Calculate the thermal energy transferred from the sample during the first\n \n minutes.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n
\n\n Monochromatic light of frequency\n \n is incident on the surface of a metal. The stopping voltage for this light is\n \n . When the frequency of the radiation is changed to\n \n , the stopping voltage is\n \n .\n
\n\n What is the quantity\n \n equal to?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n What is the pattern observed when white light passes through a diffraction grating?\n
\n
\n
\n \n
\n [1]\n
\n\n C\n
\n\n A loop of wire lies in a magnetic field directed into the plane of the page. The loop carries a current in a clockwise direction.\n
\n\n \n
\n The magnetic force acting on the wire tends to\n
\n\n
\n A. rotate the loop about the X axis.\n
\n B. rotate the loop about the Y axis.\n
\n\n C. reduce the radius of the loop.\n
\n\n D. increase the radius of the loop.\n
\n\n [1]\n
\n\n D\n
\n\n A relatively complicated application of the right-hand rule for the direction of the magnetic force on a current-carrying wire. The wire is not straight, and the rule should only be applied to a short section of the loop at one particular position, e.g. at the leftmost point of the loop. The force on this short section is directed outward from the center, and the symmetry argument shows that the same is true elsewhere around the loop. This question had a particularly large performance gap between HL and SL candidates.\n
\n\n Calculate the average translational speed of air molecules.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «m s\n \n −1\n \n » ✓\n
\n\n \n Calculate the average force exerted by the racquet on the ball.\n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n \n \n \n \n \n =\n \n \n \n 148«\n \n \n \n »≈150«\n \n \n \n \n \n » ✔\n \n
\n\n
\n\n At both HL and SL many candidates scored both marks for correctly answering this. A straightforward start to the paper. For those not gaining both marks it was possible to gain some credit for calculating either the change in momentum or the acceleration. At SL some used 64 ms-1 as a value for a and continued to use this value over the next few parts to the question.\n
\n\n Predict the charge on each sphere.\n
\n\n [3]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n so\n \n «μC»,\n \n «μC» ✓\n
\n\n
\n\n \n Award\n \n [3]\n \n marks for a bald correct answer.\n \n
\n\n \n Discuss, by reference to the kinetic model of an ideal gas and the answer to (c)(i), whether the assumption that helium behaves as an ideal gas is justified.\n \n
\n\n [2]\n
\n\n \n «For an ideal gas» the size of the particles is small compared to the distance between them/size of the container/gas\n \n
\n\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» the volume of the particles is negligible/the volume of the particles is small compared to the volume of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» particles are assumed to be point objects ✔\n \n
\n\n \n calculation/ratio/result in (c)(i) shows that volume of helium atoms is negligible compared to/much smaller than volume of helium gas/container «hence assumption is justified» ✔\n \n
\n\n At HL candidates seemed more able to focus on the key part feature of the question, which was the nature of the volumes involved. Examiners were looking for an assumption of the kinetic theory related to the volume of the atoms/gas and then a link to the ratio calculated in ci). The command terms were slightly different at SL and HL, giving slightly more guidance at SL.\n
\n\n A flywheel of moment of inertia 0.50 kg m\n \n 2\n \n rotates anti-clockwise with an initial angular velocity of 15 rad s\n \n −1\n \n . A torque is applied to the flywheel and its angular velocity changes to 25 rad s\n \n −1\n \n , rotating clockwise.\n
\n\n \n
\n What is the angular impulse delivered to the flywheel?\n
\n\n
\n A. 5.0 N m s\n
\n B. 10 N m s\n
\n\n C. 20 N m s\n
\n\n D. 40 N m s\n
\n\n [1]\n
\n\n C\n
\n\n An object is submerged in a fluid. Three quantities relating to this situation are\n
\n\n I. the density of the object\n
\n II. the density of the fluid\n
\n III. the gravitational field strength\n
\n On which quantities does the buoyancy force acting on the object depend?\n
\n\n
\n A. I and II\n
\n B. I and III\n
\n\n C. II and III\n
\n\n D. I, II and II\n
\n\n [1]\n
\n\n C\n
\n\n Sketch a graph to show how the acceleration of point P varies with its displacement from the rest position.\n
\n\n \n
\n [1]\n
\n\n straight line through origin with negative gradient\n \n ✓\n \n
\n\n The metal plate is replaced by a wooden plate that reflects a lower intensity sound wave than the metal plate.\n
\n\n State and explain the differences between the sound intensities detected by the same microphone with the metal plate and the wooden plate.\n
\n\n [3]\n
\n\n relates intensity to amplitude ✓\n
\n\n antinodes / maximum intensity will be decreased / quieter ✓\n
\n\n nodes / minimum will be increased / louder ✓\n
\n\n difference in intensities will be less ✓\n
\n\n maxima and minima are at the same positions ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n The albedo of the Earth’s atmosphere is 0.28. Outline why the maximum temperature of a black body on the Earth when the Sun is overhead is less than that at point A on the Moon.\n
\n\n [1]\n
\n\n (28 %) of sun’s energy is scattered/reflected by earth’s atmosphere\n \n \n OR\n \n \n only 72 % of incident energy gets absorbed by blackbody ✔\n
\n\n \n Must be clear that the energy is being scattered by the atmosphere.\n \n
\n\n \n Award\n \n [0]\n \n for simple definition of “albedo”\n \n .\n
\n\n This question was assessing the understanding of the concept of albedo. Many candidates were able to connect that an albedo of 0.28 meant that 28 % of the incident energy from the sun was being reflected or scattered by the atmosphere before reaching the black body.\n
\n\n Calculate, in MeV, the energy released in the reaction.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n 169 «MeV» ✓\n
\n\n determine the tension in the string.\n
\n\n [2]\n
\n\n \n T − mg = F\n \n net\n \n \n OR\n \n \n \n T − mg =\n \n \n ✓\n
\n\n \n T\n \n «= 0.800 × 9.81 +\n \n » = 23.5 «N» ✓\n
\n\n Suggest an appropriate measuring instrument for determining\n \n b\n \n .\n
\n\n [1]\n
\n\n instrument (capable of reading to 0.05 mm) with reason related to resolution of instrument ✓\n
\n\n \n eg micrometer screw gauge, Vernier caliper, travelling microscope\n \n
\n\n Calculate the maximum current in the chamber due to the electrons when there is no smoke in the chamber.\n
\n\n [3]\n
\n\n Each alpha gives rise to\n \n ion pairs ✓\n
\n\n So\n \n ion pairs per second ✓\n
\n\n current\n \n «A» ✓\n
\n\n State what will happen to the intensity of the secondary maxima.\n
\n\n [1]\n
\n\n decreases ✓\n
\n\n The molar mass of water is 18 g mol\n \n −1\n \n . Estimate the average speed of the water molecules in the vapor produced. Assume the vapor behaves as an ideal gas.\n
\n\n [2]\n
\n\n \n E\n \n \n k\n \n = «\n \n » =\n \n «J»\n \n ✓\n \n
\n\n \n v =\n \n «\n \n \n \n »\n \n =\n \n 720 «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n State the initial acceleration of the raindrop.\n
\n\n [1]\n
\n\n \n g\n \n \n \n OR\n \n \n 9.81 «m s\n \n −2\n \n »\n \n \n OR\n \n \n acceleration of gravity/due to free fall ✓\n
\n\n
\n\n \n Accept 10 «\n \n m s\n \n −2\n \n \n ».\n \n
\n\n \n Ignore sign.\n \n
\n\n \n Do\n \n not\n \n accept bald “gravity”.\n \n
\n\n \n Accept answer that indicates tangent of the graph at time t=0.\n \n
\n\n A nice introductory question answered correctly by most candidates. Most answers quoted the data booklet value, with a few 10's or 9.8's, or the answer in words. Very few lost the mark by just stating gravity, or zero.\n
\n\n Two resistors of equal resistance R are connected with two cells of emf\n \n ε\n \n and 2\n \n ε\n \n . Both cells have negligible internal resistance.\n
\n\n \n
\n What is the current in the resistor labelled X?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n The angular speed of the flywheel increased by 280 rad s\n \n −1\n \n during the application of the angular impulse.\n
\n\n Determine the moment of inertia of the flywheel.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n 2.6 kg m\n \n 2\n \n ✓\n
\n\n The work done during the isothermal expansion A → B is 540 J. Calculate the thermal energy that leaves the gas during one cycle.\n
\n\n [2]\n
\n\n heat into gas «is along AB» and equals\n
\n\n \n Q\n \n in\n \n \n «= Δ\n \n U\n \n +\n \n W\n \n = 0 + 540» = 540 «J» ✔\n
\n\n heat out is (1−\n \n e\n \n )\n \n Q\n \n in =\n \n \n (1−0.45) × 540 = 297 «J» ≈ 3.0 × 10\n \n 2\n \n «J» ✔\n
\n\n \n Award\n \n [2]\n \n for bald correct answer.\n \n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n A magnet connected to a spring oscillates above a solenoid with a 240 turn coil as shown.\n
\n\n \n
\n The graph below shows the variation with time\n \n of the emf across the solenoid with the period,\n \n , of the system shown.\n
\n\n \n
\n The spring is replaced with one that allows the magnet to oscillate with a higher frequency. Which graph shows the new variation with time\n \n of the current\n \n in the resistor for this new set-up?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Two parallel plates are a distance apart with a potential difference between them. A point charge moves from the negatively charged plate to the positively charged plate. The charge gains kinetic energy\n \n W\n \n . The distance between the plates is doubled and the potential difference between them is halved. What is the kinetic energy gained by an identical charge moving between these plates?\n
\n\n A.\n \n \n \n
\n\n B.\n \n W\n \n
\n\n C. 2\n \n W\n \n
\n\n D. 4\n \n W\n \n
\n\n [1]\n
\n\n A\n
\n\n The correct response (A) was the most common from candidates, however a significant number of candidates appeared unsure of the impact of the distance between plates and (incorrectly) selected response B.\n
\n\n Outline, using (b)(i), why it is not correct to use the equation\n \n to calculate the speed required for the spacecraft to reach infinity from the surface of\n \n .\n
\n\n [1]\n
\n\n «this is the escape speed for\n \n alone but» gravitational potential / field of Jupiter must be taken into account\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n State what is meant by an ideal voltmeter.\n
\n\n [1]\n
\n\n infinite resistance\n
\n\n \n \n OR\n \n \n
\n\n no current is flowing through it ✓\n
\n\n A majority of candidates scored a mark by simply stating infinite resistance. Several answers went the other way round, stating a resistance of zero.\n
\n\n An object with a moment of inertia of 12 kg m\n \n 2\n \n is rotating about its axis of rotation with an angular speed of 15 rad s\n \n −1\n \n . A torque is applied to the object so that its angular speed increases to 50 rad s\n \n −1\n \n .\n
\n\n What angular impulse acted on the object?\n
\n
\n
\n A. 420 kg m s\n \n −1\n \n
\n\n B. 780 kg m s\n \n −1\n \n
\n\n C. 390 kg m s\n \n −1\n \n
\n\n D. 210 kg m s\n \n −1\n \n
\n\n [1]\n
\n\n A\n
\n\n Explain why the work done by the gas during the isothermal expansion AB is less than the work done on the gas during the adiabatic compression BC.\n
\n\n [1]\n
\n\n area under curve AB is less than area under curve BC ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from part\n \n (b)\n \n \n
\n\n According to laboratory observers\n \n .\n
\n\n Calculate\n \n D\n \n .\n
\n\n [2]\n
\n\n \n = 2.00 × 1.56 × 10\n \n −6\n \n or 3.12 × 10\n \n −6\n \n s ✓\n
\n\n \n D\n \n = «3.12 × 10\n \n −6\n \n × 0.866 × 3 × 10\n \n 8\n \n =» 811 m\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n The kinetic energy of a body is determined from measurements of its momentum\n \n p\n \n and its mass\n \n m\n \n .\n
\n\n The percentage uncertainties in the measurements are:\n
\n| \n \n p\n \n | \n\n ± 3 %\n | \n
| \n \n m\n \n | \n\n ± 4 %\n | \n
\n What is the percentage uncertainty in the kinetic energy?\n
\n\n
\n A. 7 %\n
\n B. 10 %\n
\n\n C. 13 %\n
\n\n D. 14 %\n
\n\n [1]\n
\n\n B\n
\n\n State what will happen to the angular position of the primary maxima.\n
\n\n [1]\n
\n\n stays the same ✓\n
\n\n Calculate, in s\n \n −1\n \n , the initial activity of the sample.\n
\n\n [1]\n
\n\n \n «s\n \n −1\n \n » ✓\n
\n\n \n Show that the intensity radiated by the oceans is about 400 W m\n \n -2\n \n .\n \n
\n\n [1]\n
\n\n \n 5.67\n \n ×\n \n 10\n \n \n −\n \n 8\n \n × 289\n \n 4\n \n \n
\n\n \n \n \n OR\n \n \n
\n \n
\n \n = 396«\n \n W m\n \n −\n \n \n \n 2\n \n » ✔\n
\n \n
\n \n «\n \n ≈\n \n 400\n \n W m\n \n −\n \n \n \n 2\n \n »\n \n
\n\n This was well answered with candidates scoring the mark for either a correct substitution or an answer given to at least one more sf than the show that value. Some candidates used 298 rather than 289.\n
\n\n According to laboratory observers\n \n .\n
\n\n Calculate\n \n D\n \n .\n
\n\n [2]\n
\n\n \n = 2.00 × 1.56 × 10\n \n −6\n \n or 3.12 × 10\n \n −6\n \n s ✓\n
\n\n \n D\n \n = «3.12 × 10\n \n −6\n \n × 0.866 × 3 × 10\n \n 8\n \n =» 811 m\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n Explain why the change of entropy for the gas during the process BC is equal to zero.\n
\n\n [1]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «the process is adiabatic so» ΔQ = 0 ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n The compression is reversible «so ΔS = 0» ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Draw, on the axes, the graph to show how the kinetic energy of the cylinder varies with time during\n \n one\n \n period of oscillation\n \n .\n
\n\n \n
\n [2]\n
\n\n \n energy never negative\n \n \n ✓\n \n
\n\n \n correct shape with two maxima\n \n \n ✓\n \n
\n\n \n
\n Most candidates answered with a graph that was only positive so scored the first mark.\n
\n\n A solid sphere of radius\n \n and mass\n \n is released from rest and rolls down a slope, without slipping. The vertical height of the slope is\n \n . The moment of inertia\n \n of this sphere about an axis through its centre is\n \n .\n
\n\n \n
\n Show that the linear velocity\n \n of the sphere as it leaves the slope is\n \n .\n
\n\n [3]\n
\n\n \n conservation of rotational and linear energy\n \n
\n\n \n \n OR\n
\n \n \n \n ✓\n
\n
\n\n \n using\n \n \n \n AND\n \n \n \n ✓\n \n
\n\n \n with\n \n \n \n correct manipulation\n \n \n \n to find the requested relationship\n \n \n ✓\n \n
\n\n A solid is heated at constant power in an insulated container. The graph shows the variation of temperature with time.\n
\n\n \n
\n Why is the temperature constant for section QR?\n
\n\n
\n A. The intermolecular potential energy of the molecules is constant.\n
\n B. The kinetic energy of the molecules is constant.\n
\n\n C. The internal energy of the solid is constant.\n
\n\n D. The rate at which the solid absorbs heat is equal to the rate at which it loses heat.\n
\n\n [1]\n
\n\n B\n
\n\n The mass of the wire is 18 g. The specific heat capacity of copper is 385 J kg\n \n −1\n \n K\n \n −1\n \n . Estimate the increase in temperature of the wire.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «K» ✓\n
\n\n
\n\n \n Allow\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Award\n \n [1]\n \n for a\n \n POT\n \n error in\n \n MP1\n \n .\n \n
\n\n Show that the intensity of the solar radiation at the location of Titan is 16 W m\n \n −2\n \n
\n\n [1]\n
\n\n incident intensity\n \n \n \n OR\n \n \n \n «W m\n \n −2\n \n » ✓\n
\n\n
\n\n \n Allow the use of 1400 for the solar constant.\n \n
\n\n Determine the mass of the gas in the container.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n An ideal gas expands isothermally. The work done by the gas is 100 J. What is the change in the internal energy of the gas?\n
\n\n
\n A. −100 J\n
\n B. 0\n
\n\n C. +50 J\n
\n\n D. +100 J\n
\n\n [1]\n
\n\n B\n
\n\n \n The percentage uncertainty for\n \n \n \n \n \n is\n \n . State\n \n \n \n \n \n , with its absolute uncertainty.\n \n
\n\n [2]\n
\n\n \n «\n \n of\n \n » =\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n «\n \n of\n \n » =\n \n \n \n ✓\n
\n \n
\n \n rounds uncertainty to 1sf\n
\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n \n \n \n ✓\n \n
\n
\n\n \n \n Allow ECF from (b)(i)\n
\n Award\n \n \n \n [2]\n \n \n \n marks for a bald correct answer\n \n \n
\n Well answered. A significant number did not round the uncertainty to match the value of gamma.\n
\n\n A wave of period 10 ms travels through a medium. The graph shows the variation of particle displacement with distance for the wave.\n
\n\n \n
\n What is the average speed of a particle in the medium during one cycle?\n
\n\n A. 4.0 m s\n \n −1\n \n
\n\n B. 8.0 m s\n \n −1\n \n
\n\n C. 16 m s\n \n −1\n \n
\n\n D. 20 m s\n \n −1\n \n
\n\n [1]\n
\n\n C\n
\n\n Option D was a very efficient distractor as the most common (incorrect) selection by both HL and SL candidates. The difficulty index was low for this question, suggesting that HL and SL candidates found this question quite challenging. Candidates are again encouraged to read the questions carefully; it is likely that candidates selecting option D were providing the wave speed rather than particle speed.\n
\n\n Which of the formulae represents Newton’s second law?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n This question was very well answered by SL candidates, as demonstrated by the high difficulty index.\n
\n\n Outline what is meant by an isotope.\n
\n\n [1]\n
\n\n «An atom with» the same number of protons\n \n \n AND\n \n \n different numbers of neutrons\n
\n \n \n OR\n \n \n
\n Same chemical properties\n \n \n AND\n \n \n different physical properties ✓\n
\n \n Do\n \n not\n \n allow just atomic number and mass number\n \n
\n\n \n A solid sphere of mass 1.5 kg is rolling, without slipping, on a horizontal surface with a speed of 0.50 m s\n \n -1\n \n . The sphere then rolls, without slipping, down a ramp to reach a horizontal surface that is 45 cm lower.\n \n
\n\n \n \n \n
\n \n \n Calculate the speed of the sphere at the bottom of the ramp.\n \n \n
\n\n [3]\n
\n\n Initial\n \n \n \n \n «=0.26J» ✔\n \n
\n\n Final\n \n \n \n \n \n «=6.88J»\n \n \n ✔\n \n \n
\n\n \n \n \n \n \n \n «m s\n \n –1\n \n » ✔\n \n \n \n
\n\n
\n\n \n Other solution methods are possible.\n \n
\n\n
\n\n Although there were many correct answers, many candidates forgot to include the initial kinetic energy of the ball at the top of the ramp. The process followed to obtain the answer was too often poorly presented, candidates are encouraged to explain what is being calculated rather than just writing numbers.\n
\n\n \n Determine, using the graph, the emf of the cell including the uncertainty for this value. Give your answer to the correct number of significant figures.\n \n
\n\n [3]\n
\n\n \n evidence that ε can be determined from the y-intercept of the line of best-fit or lines of min and max gradient ✔\n
\n \n
\n \n states ε=1.59\n \n \n OR\n \n \n 1.60\n \n \n OR\n \n \n 1.61V«» ✔\n
\n \n
\n \n states uncertainty in ε is 0.02 V«»\n \n \n OR\n \n \n 0.03«V» ✔\n \n
\n\n The number of candidates who realised that the V intercept was EMF was disappointing. Large numbers of candidates tried to calculate ε using points on the graph, often ending up with unrealistic values. Another common mistake was not giving values of ε and Δε to the correct number of digits - 2 decimal places on this occasion. Very few candidates drew maximum and minimum gradient lines as a way of determining Δε.\n
\n\n Which graph represents the variation with displacement of the potential energy\n \n P\n \n and the total energy\n \n T\n \n of a system undergoing simple harmonic motion (SHM)?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n A mass oscillating in simple harmonic motion on the end of a spring has an amplitude\n \n \n 0\n \n and a total energy\n \n E\n \n \n T\n \n . The mass on the spring is doubled and made to oscillate with the same amplitude\n \n \n 0\n \n .\n
\n\n What is the total energy of the oscillating system after the change?\n
\n\n
\n A.\n \n E\n \n \n T\n \n
\n B.\n \n \n E\n \n \n T\n \n
\n\n C. 2\n \n E\n \n \n T\n \n
\n\n D. 4\n \n E\n \n \n T\n \n
\n\n [1]\n
\n\n A\n
\n\n Calculate the period of oscillations of\n \n q\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n .\n \n
\n\n A cylinder of mass\n \n \n \n and radius\n \n \n \n rotates at constant angular speed\n \n ω\n \n about an axis through its centre. The rotational kinetic energy of the cylinder is\n \n K\n \n .\n
\n\n The moment of inertia of the cylinder is\n \n .\n
\n\n \n
\n A second cylinder has mass\n \n , radius\n \n and rotates with angular speed 2\n \n ω\n \n .\n
\n\n What is the rotational kinetic energy of the second cylinder?\n
\n\n
\n A. 8\n \n K\n \n
\n B. 16\n \n K\n \n
\n\n C. 32\n \n K\n \n
\n\n D. 64\n \n K\n \n
\n\n [1]\n
\n\n C\n
\n\n Sketch a graph to show how the acceleration of point P varies with its displacement from the rest position.\n
\n\n \n
\n [1]\n
\n\n straight line through origin with negative gradient\n \n ✓\n \n
\n\n Outline why a force acts on the Moon.\n
\n\n [1]\n
\n\n gravitational attraction/force/field «of the planet/Moon» ✔\n
\n\n \n Do not accept “gravity”\n \n .\n
\n\n This was generally well answered, although some candidates simply used the vague term “gravity” rather than specifying that it is a gravitational force or a gravitational field. Candidates need to be reminded about using proper physics terms and not more general, “every day” terms on the exam.\n
\n\n The refractive index of glass is\n \n and the refractive index of water is\n \n . What is the critical angle for light travelling from glass to water?\n
\n\n A.\n \n
\n
\n B.\n \n
\n
\n C.\n \n
\n
\n D.\n \n
\n [1]\n
\n\n D\n
\n\n The black-body radiation curve of an object at 600 K is shown. The intensity units are arbitrary.\n
\n\n \n
\n What is the radiation curve of the same object at 450 K?\n
\n\n The original curve is shown with a dashed line.\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n A simple model of an atom has three energy levels. The differences between adjacent energy levels are shown below.\n
\n\n \n
\n What are the two smallest frequencies in the emission spectrum of this atom?\n
\n\n A. 0.5 × 10\n \n 15\n \n Hz and 1.0 × 10\n \n 15\n \n Hz\n
\n\n B. 0.5 × 10\n \n 15\n \n Hz and 1.5 × 10\n \n 15\n \n Hz\n
\n\n C. 1.0 × 10\n \n 15\n \n Hz and 2.0 × 10\n \n 15\n \n Hz\n
\n\n D. 1.0 × 10\n \n 15\n \n Hz and 3.0 × 10\n \n 15\n \n Hz\n
\n\n [1]\n
\n\n C\n
\n\n State what is meant by an elastic collision.\n
\n\n [1]\n
\n\n No change in the kinetic energy of the system ✓\n
\n\n \n Outline why the normal force acting on the ladder at the point of contact with the wall is equal to the frictional force\n \n F\n \n between the ladder and the ground.\n \n
\n\n [1]\n
\n\n \n «translational equilibrium demands that the»\n \n \n resultant force in the horizontal direction must be zero✔\n
\n \n
\n \n «hence\n \n N\n \n \n W\n \n =\n \n F»\n \n \n
\n\n \n \n \n Equality of forces is given, look for reason why.\n \n \n \n
\n\n Many candidates stated that the resultant of all forces must be zero but failed to mention the fact that horizontal forces must balance in this particular question.\n
\n\n Show that the surface temperature of\n \n δ\n \n Vel A is about 9000 K.\n
\n\n [1]\n
\n\n correct substitution into\n \n OR 9350 K ✓\n
\n\n Describe, in terms of electron flow, how the smaller sphere becomes charged.\n
\n\n [1]\n
\n\n electrons leave the small sphere «making it positively charged» ✓\n
\n\n A photon of wavelength\n \n scatters off an electron at rest. The scattered photon has wavelength\n \n .\n
\n\n What is the fraction of the incident photon energy that gets transferred to the electron?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The variation of\n \n d\n \n with\n \n W\n \n is shown.\n
\n\n \n
\n Outline\n \n one\n \n experimental reason why the graph does not go through the origin.\n
\n\n [1]\n
\n\n beam bends under its own weight / weight of pan\n
\n\n \n \n OR\n \n \n
\n\n specified systematic error in\n \n d\n \n ✓\n
\n\n Calculate the maximum current in the chamber due to the electrons when there is no smoke in the chamber.\n
\n\n [3]\n
\n\n Each alpha gives rise to\n \n ion pairs ✓\n
\n\n So\n \n ion pairs per second ✓\n
\n\n current\n \n «A» ✓\n
\n\n Four of the energy states for an atom are shown. Transition between any two states is possible.\n
\n\n \n
\n What is the shortest wavelength of radiation that can be emitted from these four states?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n State the nature and direction of the force that accelerates the 15 kg object.\n
\n\n [1]\n
\n\n static friction force «between blocks»\n
\n\n \n AND\n \n
\n\n directed to the right ✓\n
\n\n Outline\n \n one\n \n difference between a standing wave and a travelling wave.\n
\n\n [1]\n
\n\n travelling waves transfer energy\n \n \n OR\n \n \n standing waves don’t ✓\n
\n\n amplitude of oscillation varies along a standing wave\n \n \n OR\n \n \n is constant along a travelling wave ✓\n
\n\n standing waves have nodes / antinodes\n \n \n OR\n \n \n travelling waves don’t ✓\n
\n\n points in an internodal region have same phase in standing waves\n \n \n OR\n \n \n different phase in travelling waves ✓\n
\n\n This question was answered well. Students showed to be familiar with the differences between standing and travelling waves.\n
\n\n A sample contains 5.0 g of pure polonium-210. The decay constant of polonium-210 is 5.8 × 10\n \n −8\n \n s\n \n −1\n \n . Lead-206 is stable.\n
\n\n Calculate the mass of lead-206 present in the sample after one year.\n
\n\n [3]\n
\n\n undecayed mass\n \n «\n \n g» ✓\n
\n\n mass of decayed polonium «\n \n undecayed mass»\n \n «g» ✓\n
\n\n mass of lead «\n \n »\n \n «g» ✓\n
\n\n
\n\n \n Allow\n \n [2] max\n \n for answers that ignore mass difference between Pb and Po (4.2 g).\n \n
\n\n \n Allow calculations in number of particles or moles for\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n Several answers referred incorrectly to electron energy levels. Successful candidates managed to score full marks, although it was also common to miss the relationship between energy and wavelength.\n
\n\n Two long parallel wires P and Q are a distance\n \n d\n \n apart. They each carry a current.\n
\n\n A magnetic force per unit length\n \n acts on P due to Q.\n
\n\n The distance between the wires is increased to 2\n \n d\n \n and the current in Q is decreased to\n \n .\n
\n\n \n
\n What is the magnetic force per unit length that acts on P due to Q after the changes?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n \n two\n \n difficulties of energy production by nuclear fusion.\n
\n\n [2]\n
\n\n Requires high temp/pressure ✓\n
\n Must overcome Coulomb/intermolecular repulsion ✓\n
\n Difficult to contain / control «at high temp/pressure» ✓\n
\n Difficult to produce excess energy/often energy input greater than output /\n \n \n OWTTE\n \n \n ✓\n
\n Difficult to capture energy from fusion reactions ✓\n
\n Difficult to maintain/sustain a constant reaction rate ✓\n
\n A ball rolls on the floor towards a wall and rebounds with the same speed and at the same angle to the wall.\n
\n\n \n
\n What is the direction of the impulse applied to the ball by the wall?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n Three statements about the atom are:\n
\n\n I. The nucleus of the atom is positively charged.\n
\n\n II. The electrons provide only a small fraction of the mass of an atom.\n
\n\n III. Most of the atom is free space.\n
\n\n Which statements are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n Light of wavelength\n \n \n \n is diffracted after passing through a very narrow single slit of width\n \n \n \n . The intensity of the central maximum of the diffracted light is\n \n . The slit width is doubled.\n
\n\n What is the intensity of central maximum and the angular position of the first minimum?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Option B was the most frequent (correct) selected by candidates. Interestingly, the more able candidates were distracted by option D, who were likely considering the intensity/amplitude relationship. As a result, this would be a good MC question for teaching purposes.\n
\n\n Calculate the largest fractional uncertainty in\n \n T\n \n for these data.\n
\n\n [2]\n
\n\n \n T\n \n = 0.5 s ✓\n
\n\n «\n \n » 0.2 ✓\n
\n\n The magnitude of the net force on\n \n q\n \n is given by\n \n . Explain why the charge\n \n q\n \n will execute simple harmonic oscillations about C.\n
\n\n [2]\n
\n\n The restoring force/acceleration is opposite to the displacement/towards equilibrium /\n \n \n OWTTE\n \n \n ✓\n
\n\n and proportional to displacement from equilibrium /\n \n \n OWTTE✓\n \n \n
\n\n \n Allow discussions based on the diagram (such as towards C for towards equilibrium).\n \n
\n\n \n Accept F ∝ x\n \n OR\n \n a ∝ x for\n \n MP2\n \n \n
\n\n A balloon of volume\n \n V\n \n contains 10 mg of an ideal gas at a pressure\n \n P\n \n . An additional mass of the gas is added without changing the temperature of the balloon. This change causes the volume to increase to 2\n \n V\n \n and the pressure to increase to 3\n \n P\n \n .\n
\n\n What is the mass of gas\n \n added\n \n to the balloon?\n
\n\n
\n A. 5 mg\n
\n B. 15 mg\n
\n\n C. 50 mg\n
\n\n D. 60 mg\n
\n\n [1]\n
\n\n C\n
\n\n A driver uses the brakes on a car to descend a hill at constant speed. What is correct about the internal energy of the brake discs?\n
\n\n A. The internal energy increases.\n
\n\n B. The internal energy decreases.\n
\n\n C. There is no change in the internal energy.\n
\n\n D. The internal energy is zero.\n
\n\n [1]\n
\n\n A\n
\n\n This question was well answered by HL and SL candidates, although option C did prove to be a distraction for some.\n
\n\n \n Calculate the time it takes the tennis ball to reach the net.\n \n
\n\n [2]\n
\n\n \n horizontal component of velocity is\n \n \n \n «\n \n \n \n » ✔\n
\n \n
\n \n \n \n \n \n \n «\n \n \n \n »\n \n \n \n «\n \n \n \n » ✔\n \n \n \n
\n\n
\n\n This question scored well at HL but less so at SL. One common mistake was to calculate the direct distance to the top of the net and assume that the ball travelled that distance with constant speed. At SL particularly, another was to consider the motion only when the ball is in contact with the racquet.\n
\n\n Photons of wavelength 468 nm are incident on a metallic surface. The maximum kinetic energy of the emitted electrons is 1.8 eV.\n
\n\n Calculate\n
\n\n
\n\n Use of\n \n E\n \n \n max\n \n =\n \n \n E\n \n \n max\n \n ✓\n
\n\n \n «\n \n −\n \n E\n \n \n max\n \n =\n \n − 1.81» = 0.85625\n \n 0.86 «eV» ✓\n
\n\n
\n\n Calculate the average translational speed of the gas particles.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n An object is released from rest at X and slides to Y. The vertical distance between X and Y is 10 m. During the motion, 20 % of the object’s initial gravitational potential energy is lost as friction.\n
\n\n \n
\n What is the speed of the object at Y?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n P and S are two points on a gravitational equipotential surface around a planet. Q and R are two points on a different gravitational equipotential surface at a greater distance from the planet.\n
\n\n \n
\n The greatest work done by the gravitational force is when moving a mass from\n
\n\n A. P to S.\n
\n\n B. Q to R.\n
\n\n C. R to P.\n
\n\n D. S to R.\n
\n\n [1]\n
\n\n C\n
\n\n the mechanical power output of the motor.\n
\n\n [2]\n
\n\n Power input = 457 × 600 = 274 kW ✓\n
\n\n Power output = 0.9 × 274 = 247 kW ✓\n
\n\n The separation of adjacent slits is\n \n d\n \n . Show that for the second-order diffraction maximum\n \n .\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n \n
\n Do\n \n not\n \n award\n \n ECF\n \n from(a)(ii).\n \n
\n Calculate the value of the centripetal force.\n
\n\n [1]\n
\n\n \n «N»\n \n ✓\n \n
\n\n The Hertzsprung–Russell diagram shows two stars,\n \n and\n \n .\n
\n\n \n
\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 4\n
\n\n D. 16\n
\n\n [1]\n
\n\n A\n
\n\n A motorcyclist is cornering on a curved race track.\n
\n\n Which combination of changes of banking angle\n \n θ\n \n and coefficient of friction\n \n μ\n \n between the tyres and road allows the motorcyclist to travel around the corner at greater speed?\n
\n\n \n
\n \n
\n [1]\n
\n\n A\n
\n\n A person lifts a total mass of 20 kg through a vertical distance of 0.60 m. The person repeats the lift\n \n n\n \n times to transfer a total energy of 6.0 × 10\n \n 4\n \n J.\n
\n\n What is\n \n n\n \n ?\n
\n\n
\n A. 5\n
\n B. 50\n
\n\n C. 500\n
\n\n D. 5000\n
\n\n [1]\n
\n\n C\n
\n\n The Sankey diagrams for a filament lamp and for an LED bulb are shown below.\n
\n\n \n
\n What is the efficiency of the filament lamp and the LED bulb?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n A fusion reaction of one nucleus of hydrogen-2 and one nucleus of hydrogen-3 converts 0.019 u to energy. A fission reaction of one nucleus of uranium-235 converts a mass of 0.190 u to energy.\n
\n\n What is the ratio\n \n ?\n
\n\n
\n\n A. 0.1\n
\n\n B. 0.2\n
\n\n C. 5\n
\n\n D. 10\n
\n\n [1]\n
\n\n C\n
\n\n The most frequently chosen alternative was (incorrect) A. This alternative represents the ratio of energies released in both reactions, but since the masses of the nuclides are so much different in fission and fusion, the ratio of specific energies\n \n cannot\n \n be equal to 0.1. Just remembering that fusion generally releases more energy than fission per unit mass of fuel should be sufficient to eliminate alternatives A and B.\n
\n\n The fusion reaction involves two isotopes of hydrogen of different masses. In this case, specific energy refers to the energy available from unit mass of a fuel containing both isotopes in the same mass proportion as in the fusion reaction. The simplest way to think about it is that the specific energy is the energy released in the reaction divided by the combined mass of the reactants, regardless of whether they are the same or different nuclides.\n
\n\n \n Calculate the speed of the ball as it leaves the racket.\n \n
\n\n [2]\n
\n\n \n links 0.84 to Δ\n \n p\n \n ✔\n \n
\n\n \n \n «\n \n » 14.5 «m s\n \n –1\n \n »✔\n
\n \n
\n \n \n NOTE: Award\n \n [2]\n \n for bald correct answer\n \n \n
\n\n An ideal gas of constant mass is heated in a container of constant volume.\n
\n\n What is the reason for the increase in pressure of the gas?\n
\n\n A. The average number of molecules per unit volume increases.\n
\n\n B. The average force per impact at the container wall increases.\n
\n\n C. Molecules collide with each other more frequently.\n
\n\n D. Molecules occupy a greater fractional volume of the container.\n
\n\n [1]\n
\n\n B\n
\n\n Many candidates chose option C which is a typical misconception that collision between molecules has something to do with pressure.\n
\n\n The distance from S1 to Y is 1.243 m and the distance from S2 to Y is 1.181 m.\n
\n
\n Determine the frequency of the microwaves.\n
\n [3]\n
\n\n path difference = 0.062 «m» ✔\n
\n\n so wavelength = 0.031 «m» ✔\n
\n\n frequency = 9.7 × 10\n \n 9\n \n «Hz» ✔\n
\n\n \n If no unit is given, assume the answer is in Hz. Accept other prefixes (eg 9.7 GHz)\n \n
\n\n \n Award\n \n [2 max]\n \n for 4.8 x 10\n \n 9\n \n Hz.\n \n
\n\n Many candidates struggled with this question. Few were able to calculate a proper path length difference, and then use that to calculate the wavelength and frequency. Many candidates went down blind paths of trying various equations from the data booklet, and some seemed to believe that the wavelength is just the reciprocal of the frequency.\n
\n\n Show that each resistor has a resistance of about 30 Ω.\n
\n\n [1]\n
\n\n \n «Ω»\n \n ✓\n \n
\n\n \n Must see either the substituted values\n \n OR\n \n a value for R to at least three s.f.\n \n
\n\n
\n\n Three statements about radioactive decay are:\n
\n\n I. The rate of decay is exponential.\n
\n II. It is unaffected by temperature and pressure.\n
\n III. The decay of individual nuclei cannot be predicted.\n
\n Which statements are correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n Option B was the most frequent answer by candidates, suggesting that many candidates are unclear about the basic characteristics of radioactive decay.\n
\n\n \n The student hypothesizes that the relationship between\n \n T\n \n and\n \n v\n \n is\n \n T = a + bv\n \n \n 2\n \n , where\n \n a\n \n and\n \n b\n \n are constants. To verify this hypothesis a graph showing the variation of\n \n T\n \n with\n \n v\n \n \n 2\n \n is plotted. The graph shows the data and the line of best fit.\n \n
\n\n \n \n \n
\n \n \n Determine\n \n b\n \n , giving an appropriate unit for\n \n b\n \n .\n \n \n
\n\n [3]\n
\n\n use of 2 correct points on the line with Δ\n \n v\n \n \n 2\n \n > 2 ✔\n
\n\n \n b\n \n in range 0.012 to 0.013 ✔\n
\n\n s\n \n 3\n \n m\n \n –2\n \n ✔\n
\n\n Calculate the speed of waves on the string.\n
\n\n [2]\n
\n\n wavelength\n \n «m» ✓\n
\n\n speed\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from incorrect wavelength.\n \n
\n\n This was well answered, particularly MP1 to determine the wavelength, although several candidates misinterpreted the unit of time and obtained a very small value for the velocity of the wave.\n
\n\n the number of revolutions made by the rod until it stops rotating.\n
\n\n [2]\n
\n\n \n θ\n \n =\n \n = 27.0 rad ✓\n
\n\n \n N\n \n =\n \n = 4.3 ✓\n
\n\n \n State the number of all other points on the string that have the same amplitude and phase as X.\n \n
\n\n [1]\n
\n\n \n 3 «points» ✔\n \n
\n\n P and Q leave the same point, travelling in the same direction. The graphs show the variation with time\n \n of velocity\n \n for both P and Q.\n
\n\n \n
\n What is the distance between P and Q when\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n What was a reason to postulate the existence of neutrinos?\n
\n\n A. Nuclear energy levels had a continuous spectrum.\n
\n\n B. The photon emission spectrum only contained specific wavelengths.\n
\n\n C. Some particles were indistinguishable from their antiparticle.\n
\n\n D. The energy of emitted beta particles had a continuous spectrum.\n
\n\n [1]\n
\n\n D\n
\n\n \n An object at the end of a spring oscillates vertically with simple harmonic motion (shm). The graph shows the variation with time\n \n \n \n of the displacement\n \n \n \n \n \n of the object.\n \n
\n\n \n \n \n
\n \n \n What is the velocity of the object?\n \n \n
\n\n \n \n A.\n \n \n \n \n \n
\n\n \n \n B.\n \n \n \n \n \n
\n\n \n \n C.\n \n \n \n \n \n
\n\n \n \n D.\n \n \n \n \n \n
\n\n [1]\n
\n\n B\n
\n\n A string is fixed at both ends. P and Q are two particles on the string.\n
\n\n \n
\n The first harmonic standing wave is formed in the string. What is correct about the motion of P and Q?\n
\n\n
\n A. P is a node and Q is an antinode.\n
\n B. P is an antinode and Q is a node.\n
\n\n C. P and Q oscillate with the same amplitude.\n
\n\n D. P and Q oscillate with the same frequency.\n
\n\n [1]\n
\n\n D\n
\n\n Explain, by reference to the vertical forces, how the raindrop reaches a constant speed.\n
\n\n [3]\n
\n\n Identification of air resistance/drag force «acting upwards» ✓\n
\n\n «that» increases with speed ✓\n
\n\n
\n «until» weight and air resistance cancel out\n
\n \n \n OR\n \n \n
\n\n net force/acceleration becomes zero ✓\n
\n\n
\n\n \n A statement as “air resistance increases with speed” scores\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n This was very well answered with most candidates scoring 3. The MP usually missed in candidates scoring 2 marks was MP2, to justify the variation of the magnitude of air resistance, although that rarely happened.\n
\n\n Calculate the largest fractional uncertainty in\n \n T\n \n for these data.\n
\n\n [2]\n
\n\n \n T\n \n = 0.5 s ✓\n
\n\n «\n \n » 0.2 ✓\n
\n\n \n The intensity of the light incident on the surface is reduced by half without changing the wavelength. Draw, on the graph, the variation of the current\n \n \n \n with potential\n \n \n \n after this change.\n \n
\n\n [2]\n
\n\n \n similar curve lower than original ✔\n
\n \n
\n \n with same horizontal intercept ✔\n \n
\n\n \n \n \n
\n Three statements about a nuclear fission reactor are:\n
\n\n I. The heat exchanger transfers energy from the fuel rods to the moderator.\n
\n II. The control rods must be good absorbers of neutrons.\n
\n III. The moderator must slow neutrons down.\n
\n Which statements about the reactor are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n C\n
\n\n The input power of an electric motor is 200 W. It is used to raise a mass of 10 kg at constant speed.\n
\n If the efficiency of the motor is 40 %, through what height will the mass be raised in 1 second?\n
\n
\n A. 0.5 m\n
\n B. 0.8 m\n
\n\n C. 1.2 m\n
\n\n D. 2.0 m\n
\n\n [1]\n
\n\n B\n
\n\n \n The graph shows the variation of velocity of a body with time along a straight line.\n \n
\n\n \n \n \n
\n \n \n What is correct for this graph?\n
\n \n \n
\n \n \n A. The maximum acceleration is at P.\n
\n \n \n
\n \n \n B. The average acceleration of the body is given by the area enclosed by the graph and time axis.\n
\n \n \n
\n \n \n C. The maximum displacement is at Q.\n
\n \n \n
\n \n \n D. The total displacement of the body is given by the area enclosed by the graph and time axis.\n \n \n
\n\n [1]\n
\n\n D\n
\n\n A tennis ball is dropped from rest from a height. It hits the ground and bounces back to a lower height. Air resistance is negligible.\n
\n\n What is correct about the collision of the tennis ball with the ground?\n
\n\n
\n A. Elastic because momentum of the system is conserved\n
\n B. Elastic because the kinetic energy of the system is conserved\n
\n\n C. Inelastic because momentum of the system is not conserved\n
\n\n D. Inelastic because the kinetic energy of the system is not conserved\n
\n\n [1]\n
\n\n D\n
\n\n For a real cell in a circuit, the terminal potential difference is at its closest to the emf when\n
\n\n A. the internal resistance is much smaller than the load resistance.\n
\n\n B. a large current flows in the circuit.\n
\n\n C. the cell is not completely discharged.\n
\n\n D. the cell is being recharged.\n
\n\n [1]\n
\n\n A\n
\n\n Two wires,\n \n and\n \n , are made of the same material and have equal length. The diameter of\n \n is twice that of\n \n .\n
\n\n What is\n \n ?\n
\n\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n The intensity of light at point O is\n \n . The distance OP is\n \n .\n
\n\n Sketch, on the axes, a graph to show the variation of the intensity of light with distance from point O on the screen. Your graph should cover the distance range from 0 to 2\n \n .\n
\n\n \n
\n [2]\n
\n\n smooth curve decreasing from\n \n to 0 between 0 and\n \n ✓\n
\n\n secondary maximum correctly placed\n \n \n AND\n \n \n of intensity less than 0.3\n \n ✓\n
\n\n \n E.g.\n \n \n
\n Most scored MP1. Many candidates scored full marks but it was common to see a maximum at 2x or a secondary maxima too high.\n
\n\n Show that the surface temperature of\n \n δ\n \n Vel A is about 9000 K.\n
\n\n [1]\n
\n\n correct substitution into\n \n OR 9350 K ✓\n
\n\n Calculate, for the cylinder, at the instant just before the block hits the ground the angular momentum.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n
\n \n
\n Δ\n \n L\n \n «= ΓΔ\n \n t\n \n =\n \n TR\n \n Δ\n \n t\n \n » =\n \n \n \n \n \n \n \n ✔\n
\n\n Δ\n \n L =\n \n 2.2J «Js»✔\n \n
\n \n
\n \n \n ALTERNATIVE 2\n \n \n
\n\n ω =<\n \n \n \n Δ\n \n t =\n \n \n \n \n \n Δt =\n \n \n \n \n \n \n = > 8.99 «rads\n \n −1\n \n » ✔\n
\n\n \n ΔL\n \n «=\n \n Iω\n \n »\n \n \n \n \n \n × 12 × 0.20\n \n 2\n \n × 8.99 = 2.2 «\n \n Js\n \n »\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n Angular speed, angular momentum and the kinetic energy of the cylinder at the instant given were successfully calculated by only the better-prepared candidates. Students were mostly able to recognize the correct expressions to use but struggled to find the angular speed in many instances. Error carried forward was very common throughout this question for students who incorrectly determined the angular velocity but understood and correctly applied the momentum and energy equations.\n
\n\n A space probe moves in a circular orbit around Earth. The kinetic energy of the probe is\n \n \n \n .\n
\n\n The probe will reach the escape speed when its\n \n kinetic\n \n energy is increased at least to:\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Calculate the percentage uncertainty in the value of\n \n A\n \n .\n
\n\n [2]\n
\n\n attempt to calculate fractional uncertainty in either\n \n a\n \n or\n \n b\n \n [0.0357, 0.0167] ✓\n
\n\n 0.0357 + 0.0167 = 0.05 = 5 % ✓\n
\n\n \n An object is held in equilibrium by three forces of magnitude\n \n F, G\n \n and\n \n H\n \n that act at a point in the same plane.\n \n
\n\n \n \n \n
\n \n \n Three equations for these forces are\n
\n \n \n
\n \n \n I.\n \n F\n \n cos\n \n θ\n \n =\n \n G\n \n
\n II.\n \n F\n \n =\n \n G\n \n cos\n \n θ\n \n +\n \n H\n \n sin\n \n θ\n \n
\n III.\n \n F\n \n =\n \n G + H\n \n \n \n
\n \n \n Which equations are correct?\n
\n \n \n
\n \n \n A. I and II only\n
\n \n \n
\n \n \n B. I and III only\n
\n \n \n
\n \n \n C. II and III only\n
\n \n \n
\n \n \n D. I, II and III\n \n \n
\n\n [1]\n
\n\n A\n
\n\n A block rests on a rough horizontal plane. A force P is applied to the block and the block moves to the right.\n
\n\n \n
\n There is a coefficient of friction\n \n giving rise to a frictional force F between the block and the plane. The force P is doubled. Will\n \n and F be unchanged or greater?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Determine the charge\n \n of the sphere.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n
\n \n ✓\n \n
\n Even though many were able to choose the appropriate formula from the data booklet they were often hampered in their use of the formula by incorrect techniques when using fractions.\n
\n\n The variation of\n \n d\n \n with\n \n W\n \n is shown.\n
\n\n \n
\n Outline\n \n one\n \n experimental reason why the graph does not go through the origin.\n
\n\n [1]\n
\n\n beam bends under its own weight / weight of pan\n
\n\n \n \n OR\n \n \n
\n\n specified systematic error in\n \n d\n \n ✓\n
\n\n Two different experiments, P and Q, generate two sets of data to confirm the proportionality of variables\n \n \n \n and\n \n \n \n . The graphs for the data from P and Q are shown. The maximum and minimum gradient lines are shown for both sets of data.\n
\n\n \n
\n What is true about the systematic error and the uncertainty of the gradient when P is compared to Q?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n Determine the maximum kinetic energy\n \n of the cylinder.\n
\n\n [2]\n
\n\n \n «\n \n \n \n is a maximum when\n \n hence\n \n \n »\n \n \n \n ✓\n \n
\n\n
\n \n \n ✓\n \n
\n A straightforward calculation with the most common mistake being missing the squared on the omega.\n
\n\n \n The coefficient of friction between the ladder and the ground is 0.400. Determine whether the ladder will slip.\n \n
\n\n [2]\n
\n\n \n maximum friction force = «\n \n 0.4 × 50N\n \n » = 20«N» ✔\n
\n \n
\n \n 14.4\n \n <\n \n 20\n \n \n AND\n \n \n so will not slip ✔\n \n
\n\n The question about the slipping of the ladder was poorly answered. The fact that the normal reaction on the floor was 50N was not known to many.\n
\n\n The polonium nucleus was stationary before the decay.\n
\n\n Show, by reference to the momentum of the particles, that the kinetic energy of the alpha particle is much greater than the kinetic energy of the lead nucleus.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n energy ratio expressed in terms of momentum, e.g.\n \n ✓\n
\n\n \n hence\n \n ✓\n
\n\n
\n\n \n «so\n \n has a much greater KE»\n
\n\n \n \n OR\n \n \n
\n\n \n «much» greater than\n \n «so\n \n has a much greater KE» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n alpha particle and lead particle have equal and opposite momenta ✓\n
\n\n so their velocities are inversely proportional to mass ✓\n
\n\n but KE ∝\n \n v\n \n \n 2\n \n «so\n \n has a much greater KE» ✓\n
\n\n Those who answered using the mass often did not get MP3 whereas those who converted to the number of particles or moles before the first calculation did, although that could be considered an unnecessary complication.\n
\n\n Determine, in J, the kinetic energy of the electron after the interaction.\n
\n\n [2]\n
\n\n (Because energy is conserved)\n
\n\n
\n \n
\n \n ✓\n
\n\n 9.6 fJ ✓\n
\n\n Calculate the theoretical equilibrium temperature of the mixture.\n
\n\n [3]\n
\n\n \n
\n\n \n
\n\n One heat capacity term correctly substituted ✓\n
\n\n latent heat correctly substituted\n \n ✓\n
\n\n \n «°C» ✓\n
\n\n A ray of light is incident on the flat side of a semi-circular glass block placed in paraffin. The ray is totally internally reflected inside the glass block as shown.\n
\n\n \n
\n The refractive index of glass is\n \n and the refractive index of paraffin is\n \n .\n
\n\n What is correct?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n While option A (correct) was the most frequent response from candidates, options B and D were significant distractors. Very few candidates selected option A, recognizing that different frequency and amplitude could not lead to zero intensity through interference.\n
\n\n \n Light of wavelength\n \n λ\n \n is normally incident on a diffraction grating of spacing 3\n \n λ\n \n . What is the angle between the two second-order maxima?\n \n
\n\n \n A.\n \n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n \n \n D. >90° so no second orders appear\n \n \n
\n\n [1]\n
\n\n C\n
\n\n Show that during an adiabatic expansion of an ideal monatomic gas the temperature\n \n \n \n \n \n and volume\n \n \n \n \n \n are given by\n
\n\n \n \n \n \n \n = constant\n
\n\n [2]\n
\n\n substitution of\n \n \n \n \n in\n \n \n \n \n ✔\n
\n\n manipulation to get result ✔\n
\n\n The algebraic manipulation required for this question was well mastered by only the better-prepared candidates. Many candidates tried to find the required formula via randomly selected equations from the data booklet.\n
\n\n Sketch a graph to show how the acceleration of point P varies with its displacement from the rest position.\n
\n\n \n
\n [1]\n
\n\n straight line through origin with negative gradient\n \n ✓\n \n
\n\n The Rutherford-Geiger-Marsden experiment shows that\n
\n\n A. alpha particles do not obey Coulomb’s law.\n
\n\n B. there is a fixed nuclear radius for each nucleus.\n
\n\n C. a large proportion of alpha particles are undeflected.\n
\n\n D. the Bohr model of the hydrogen atom is confirmed.\n
\n\n [1]\n
\n\n C\n
\n\n This has a low discrimination index but it was felt that perhaps as it was the last question students were guessing the answer especially those choosing option A.\n
\n\n Outline, by reference to Newton’s third law, how the upward lift force on the aircraft is achieved.\n
\n\n [2]\n
\n\n \n Blades exert a downward force on the air\n \n \n ✓\n \n
\n\n \n
\n air exerts an equal and opposite force on the blades\n \n \n «\n \n \n by Newton’s third law\n \n \n »\n
\n \n \n \n \n OR\n \n \n
\n \n \n air exerts a reaction force on the blades\n \n \n «\n \n \n by Newton’s third law\n \n \n »\n \n \n ✓\n \n
\n \n \n
\n Downward direction required for\n \n \n \n MP1\n \n \n \n .\n \n \n
\n The question required candidates to apply Newton's third law to a specific situation. Candidates who had learned the 'action and reaction' version of Newton's third law generally did less well than those who had learned a version describing 'object A exerting a force on object B' etc. Some answers lacked detail of what was exerting the force and in which direction.\n
\n\n State the wavelength of the photon after the interaction.\n
\n\n [1]\n
\n\n 8.43 pm ✓\n
\n\n \n Determine the speed of the tennis ball as it strikes the ground.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n
\n \n \n
\n \n Initial KE + PE = final KE /\n \n
\n\n \n \n \n \n × 0.058 × 64\n \n 2\n \n + 0.058 × 9.81 × 2.80 =\n \n \n \n \n \n \n ×\n \n 0.058\n \n ×\n \n \n v\n \n \n 2\n \n ✔\n
\n \n
\n \n \n v\n \n = 64.4 «\n \n ms\n \n −1\n \n \n » ✔\n \n \n
\n \n
\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n
\n \n \n \n \n »\n \n ✔\n \n \n
\n\n \n «\n \n \n \n »\n \n
\n\n \n \n \n \n \n »\n \n ✔\n \n \n \n
\n\n \n \n \n \n
\n\n This proved difficult for candidates at both HL and SL. Many managed to calculate the final vertical component of the velocity of the ball.\n
\n\n Discuss, with reference to the molecules in the liquid, the difference between milk at 11 °C and milk at 84 °C.\n
\n\n [2]\n
\n\n the temperature has increased so the internal energy / « average » KE «of the molecules» has increased\n \n \n OR\n \n \n temperature is proportional to average KE «of the molecules». ✓\n
\n\n «therefore» the «average» speed of the molecules or particles is higher\n \n \n OR\n \n \n more frequent collisions « between molecules »\n \n \n OR\n \n \n spacing between molecules has increased\n \n \n OR\n \n \n average force of collisions is higher\n \n \n OR\n \n \n intermolecular forces are less\n \n \n OR\n \n \n intermolecular bonds break and reform at a higher rate\n \n \n OR\n \n \n molecules are vibrating faster. ✓\n
\n\n This was generally well answered. Most HL candidates linked the increase in temperature to the increase in the kinetic energy of the molecules and were able to come up with a consequence of this change (such as the molecules moving faster). SL candidates tended to focus more on consequences, often neglecting to mention the change in KE.\n
\n\n A light source of power\n \n P\n \n is observed from a distance\n \n \n \n . The power of the source is then halved.\n
\n\n At what distance from the source will the intensity be the same as before?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n SL candidate responses were divided across options A, B and C, and so this question would be a useful teaching tool for exploring the relationship between power, intensity and distance.\n
\n\n Calculate the torque acting on the bar while it is accelerating.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n The quantity of trapped gas is 53.2 mol. Calculate the thermal energy removed from the gas during process CA.\n
\n\n [2]\n
\n\n «W = 0 so» Q = ΔU ✓\n
\n\n «ΔU =\n \n × 53.2 × R × (351 – 27) so » ΔU = 2.15 × 10\n \n 5\n \n «J» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n What statement about alpha particles, beta particles and gamma radiation is true?\n
\n\n A. Gamma radiation always travels faster than beta particles in a vacuum.\n
\n\n B. In air, beta particles produce more ions per unit length travelled than alpha particles.\n
\n\n C. Alpha particles are always emitted when beta particles are emitted.\n
\n\n D. Alpha particles are deflected in the same direction as beta particles in a magnetic field.\n
\n\n [1]\n
\n\n A\n
\n\n A thermodynamic process taking place in an isolated system is irreversible when the final state of the system has a:\n
\n\n
\n A. greater number of microstates than the initial state\n
\n B. smaller number of microstates than the initial state\n
\n\n C. greater internal energy than the initial state\n
\n\n D. smaller internal energy than the initial state\n
\n\n [1]\n
\n\n A\n
\n\n Outline the significance of conservation laws for physics.\n
\n\n [1]\n
\n\n they express fundamental principles of nature\n \n ✓\n \n
\n\n allow to model situations\n \n ✓\n \n
\n\n allow to calculate unknown variables\n \n ✓\n \n
\n\n allow to predict possible outcomes\n \n ✓\n \n
\n\n allow to predict missing quantities/particles\n \n ✓\n \n
\n\n allow comparison of different system states\n \n ✓\n \n
\n\n The heater is removed and a mass of 0.30 kg of pasta at −10 °C is added to the boiling water.\n
\n\n Determine the equilibrium temperature of the pasta and water after the pasta is added. Other heat transfers are negligible.\n
\n\n Specific heat capacity of pasta = 1.8 kJ kg\n \n −1\n \n K\n \n −1\n \n
\n Specific heat capacity of water = 4.2 kJ kg\n \n −1\n \n K\n \n −1\n \n
\n [3]\n
\n\n use of mcΔT\n \n ✓\n \n
\n\n 0.86 × 4200 × (100 –\n \n T\n \n ) = 0.3 × 1800 × (\n \n T\n \n +10)\n \n ✓\n \n
\n\n \n T\n \n \n eq\n \n = 85.69«°C» ≅ 86«°C»\n \n ✓\n \n
\n\n \n Accept T\n \n eq\n \n in Kelvin (359 K).\n \n
\n\n Two satellites are in circular orbits around the Earth. Both satellites have the same mass and satellite X is closer to Earth than satellite Y.\n
\n\n What is correct for the orbital periods of X and Y and the total energies of X and Y?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n The student then makes the ramp horizontal and applies a constant horizontal force to the box. The force is just large enough to start the box moving. The force continues to be applied after the box begins to move.\n
\n\n \n
\n Explain, with reference to the frictional force acting, why the box accelerates once it has started to move.\n
\n\n [3]\n
\n\n static coefficient of friction > dynamic/kinetic coefficient of friction / μ\n \n s\n \n > μ\n \n k\n \n ✓\n
\n\n «therefore» force of dynamic/kinetic friction will be less than the force of static friction ✓\n
\n\n
\n there will be a net / unbalanced forward force once in motion «which results in acceleration»\n
\n \n \n OR\n \n \n
\n\n reference to net F = ma ✓\n
\n\n This was an \"explain\" question, so examiners were looking for a clear line of discussion starting with a comparison of the coefficients of friction, leading to a comparison of the relative magnitudes of the forces of friction and ultimately the rise of a net force leading to an acceleration. Many candidates recognized that this was a question about the comparison between static and kinetic/dynamic friction but did not clearly specify which they were referring to in their responses. Some candidates clearly did not read the stem carefully as they referred to the mass being on an incline.\n
\n\n the final kinetic energy of the disc and the ring.\n
\n\n [2]\n
\n\n The disc has a smaller moment of inertia «because its mass is distributed closer to the axis of rotation» ✓\n
\n\n From\n \n , the disc will achieve a greater kinetic energy «because\n \n \n \n is the same for both» ✓\n
\n\n Calculate the energy lost during the collision.\n
\n\n [2]\n
\n\n \n × 0.200 × 12.0\n \n 2\n \n −\n \n (0.252) × 5.71\n \n 2\n \n ✓\n
\n\n 10.3 J ✓\n
\n\n
\n\n \n \n Award [1]\n \n for answer 11.5\n \n J\n \n that neglects moment of inertia of particle but do not penalize this omission in\n \n (d)(i)\n \n .\n \n
\n\n Explain why the output potential difference to the external circuit and the output emf of the photovoltaic cell are different.\n
\n\n
\n\n [2]\n
\n\n there is a potential difference across the internal resistance\n
\n \n \n OR\n \n \n
\n there is energy/power dissipated in the internal resistance\n \n ✓\n \n
\n when there is current «in the cell»/as charge flows «through the cell»\n \n ✓\n \n
\n\n \n
\n Allow full credit for answer based on\n \n \n
\n Describe the energy change that takes place for\n \n t\n \n > 3.0 s.\n
\n\n [1]\n
\n\n «gravitational» potential energy «of the raindrop» into thermal/internal energy «of the air» ✓\n
\n\n
\n\n \n Accept heat for thermal energy.\n \n
\n\n \n Accept into kinetic energy of air particles.\n \n
\n\n \n Ignore sound energy.\n \n
\n\n Of the wrong answers, the most common ones were gravitational potential to kinetic or the idea that because there was no change in velocity there was no energy transfer. A significant number, though, scored by identifying the change into thermal (most of them), kinetic of air particles (a few answers) or internal (very few).\n
\n\n What is evidence for wave–particle duality?\n
\n\n A. Line spectra of elements\n
\n\n B. Electron-diffraction experiments\n
\n\n C. Rutherford alpha-scattering experiments\n
\n\n D. Gamma-ray spectra\n
\n\n [1]\n
\n\n B\n
\n\n This question was generally well answered by HL candidates.\n
\n\n Estimate, using the graph, the maximum height of the bottle.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Attempt to count squares ✓\n
\n\n Area of one square found ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4 m) ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n Uses area equation for either triangle ✓\n
\n\n Correct read offs for estimate of area of triangle ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4) ✓\n
\n\n Explain the pattern seen on the screen.\n
\n\n [3]\n
\n\n Mention of interference / superposition ✓\n
\n\n Bright fringe occurs when light from the slits arrives in phase ✓\n
\n\n Dark fringe occurs when light from the slits arrives 180°/\n \n out of phase ✓\n
\n\n The astronomical unit (\n \n ) and light year (\n \n ) are convenient measures of distance in astrophysics. Define each unit.\n
\n\n \n :\n
\n\n \n :\n
\n\n [2]\n
\n\n \n \n \n :\n \n \n \n «\n \n \n average\n \n \n »\n \n \n distance from the Earth to the Sun\n \n \n ✓\n
\n \n
\n \n \n \n :\n \n distance light travels in one year\n \n \n ✓\n \n
\n\n The radius of the pulley is 2.5 cm. Calculate the angular speed of rotation of the pulley as the load hits the floor. State your answer to an appropriate number of significant figures.\n
\n\n [2]\n
\n\n use of\n \n to give 84 «rad s\n \n −1\n \n »\n
\n\n \n \n OR\n \n \n
\n\n \n to give 84 «rad s\n \n −1\n \n » ✓\n
\n\n
\n\n quoted to 2sf only✓\n
\n\n
\n\n This SL only question was generally well done. Despite some power of 10 errors, many candidates correctly reported final answer to 2 sf.\n
\n\n The design of the pad encloses the resistor in a material that traps air. The design also places the resistor close to the top surface of the pad.\n
\n\n \n
\n Explain, with reference to thermal energy transfer, why the pad is designed in this way.\n
\n\n [3]\n
\n\n Air is a poor «thermal» conductor ✓\n
\n\n Lack of convection due to air not being able to move in material ✓\n
\n\n Appropriate statement about energy transfer between the pet, the resistor and surroundings ✓\n
\n\n The rate of thermal energy transfer to the top surface is greater than the bottom «due to thinner material» ✓\n
\n\n
\n\n \n Accept air is a good insulator\n \n
\n\n A beam of negative ions flows in the plane of the page through the magnetic field due to two bar magnets.\n
\n\n \n
\n What is the direction in which the negative ions will be deflected?\n
\n\n A. Out of the page\n \n \n \n \n \n
\n\n B. Into the page X\n
\n\n C. Up the page ↑\n
\n\n D. Down the page ↓\n
\n\n [1]\n
\n\n A\n
\n\n This question was well answered by candidates.\n
\n\n Star X has a luminosity\n \n L\n \n and an apparent brightness\n \n b\n \n . Star X is at a distance\n \n \n \n from Earth.\n
\n\n Star Y has the same apparent brightness as X but is four times more luminous.\n
\n\n What is the distance of Star Y from Earth?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n the longest wavelength of a photon that will eject an electron from this surface.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n \n «\n \n =» 1.45 × 10\n \n −6\n \n «m»✓\n
\n\n \n Allow\n \n ECF\n \n from\n \n a(i)\n \n \n
\n\n Adjacent minima are separated by a distance of 0.12 m. Calculate\n \n \n \n .\n
\n\n [2]\n
\n\n wavelength = 0.24 «m» ✓\n
\n\n \n = «\n \n =» 1.4 «kHz»\n \n \n OR\n \n \n 1400 «Hz» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n Energy is transferred very slowly to ice of mass 0.050 kg at its melting point so that the ice melts completely. The melted water remains at 0 °C.\n
\n\n The specific latent heat of fusion of ice = 335 kJ kg\n \n −1\n \n
\n\n What is the entropy change of the ice?\n
\n\n
\n A. 0.041 kJ k\n \n −1\n \n
\n B. 0.061 kJ k\n \n −1\n \n
\n\n C. 0.041 J k\n \n −1\n \n
\n\n D. 0.061 J k\n \n −1\n \n
\n\n [1]\n
\n\n B\n
\n\n \n The damping of the bridge system can be varied. Draw, on the graph, a second curve when the damping is larger.\n \n
\n\n [2]\n
\n\n \n similar shape with lower amplitude ✔\n
\n \n
\n \n maximum shifted slightly to left of the original curve ✔\n \n
\n\n \n \n \n Amplitude must be lower than the original, but allow the amplitude to be equal at the extremes.\n \n \n \n
\n\n A correct curve, with lower amplitude and shifted left, was drawn by most candidates.\n
\n\n Two sets of data, shown below with circles and squares, are obtained in two experiments. The size of the error bars is the same for all points.\n
\n\n \n
\n What is correct about the absolute uncertainty and the fractional uncertainty of the\n \n y\n \n intercept of the two lines of best fit?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n The diagram shows equipotential lines for an electric field. Which arrow represents the acceleration of an electron at point P?\n
\n
\n
\n \n
\n [1]\n
\n\n D\n
\n\n Pluto is a dwarf planet of the Sun that orbits at a distance of 5.9 × 10\n \n 9\n \n km from the Sun. Determine, in years, the orbital period of Pluto.\n
\n\n [3]\n
\n\n \n used ✓\n
\n\n Earth orbital radius = 1.5 × 10\n \n 11\n \n m (from AU)\n \n AND\n \n uses 1 earth year (in any units) ✓\n
\n\n 247 years ✓\n
\n\n A satellite orbits planet\n \n with a speed\n \n at a distance\n \n from the centre of planet\n \n . Another satellite orbits planet\n \n at a speed of\n \n at a distance\n \n from the centre of planet\n \n . The mass of planet\n \n is\n \n and the mass of planet\n \n is\n \n . What is the ratio of\n \n ?\n
\n
\n A. 0.25\n
\n B. 0.5\n
\n\n C. 2.0\n
\n\n D. 4.0\n
\n\n [1]\n
\n\n B\n
\n\n A nucleus of krypton (Kr) decays to a nucleus of bromine (Br) according to the equation\n
\n\n \n
\n\n What are Y and Z?\n
\n
\n
\n \n
\n [1]\n
\n\n A\n
\n\n In the decay of polonium−210, alpha emissions can be accompanied by the emissions of gamma photons, all of the same wavelength of 1.54 × 10\n \n −12\n \n m.\n
\n\n Discuss how this observation provides evidence for discrete nuclear energy levels.\n
\n\n [3]\n
\n\n photon energy is determined by its wavelength ✓\n
\n\n
\n photons are emitted when nucleus undergoes transitions between its «nuclear» energy levels\n
\n \n \n OR\n \n \n
\n\n photon energy equals the difference between «nuclear» energy levels ✓\n
\n\n
\n photons have the same energy / a fixed value\n
\n \n \n OR\n \n \n
\n\n energy is quantized / discrete ✓\n
\n\n Many identified conservation of momentum and consequently the relative velocities but it was common to miss MP3 for correctly relating this to KE.\n
\n\n Monochromatic light is incident on a diffraction grating. The diffraction pattern from the diffraction grating is then formed on a screen.\n
\n\n Only the central maximum and the first-order maxima can be observed on the screen.\n
\n\n What change will allow the second-order maxima to be observed on the screen?\n
\n\n
\n A. Decrease the distance between the diffraction grating and the source of light\n
\n B. Increase the distance between the diffraction grating and the screen\n
\n\n C. Increase the wavelength of the monochromatic light\n
\n\n D. Reduce the number of lines per unit length of the diffraction grating\n
\n\n [1]\n
\n\n D\n
\n\n The charges\n \n Q\n \n are replaced by neutral masses\n \n M\n \n and the charge\n \n q\n \n by a neutral mass\n \n m\n \n . The mass\n \n m\n \n is displaced away from C by a small distance\n \n and released. Discuss whether the motion of\n \n m\n \n will be the same as that of\n \n q\n \n .\n
\n\n [2]\n
\n\n the net force will no longer be a restoring force/directed towards equilibrium\n
\n\n \n \n OR\n \n \n
\n\n the gravitational force is attractive/neutral mass would be pulled towards larger masses/\n \n \n OWTTE\n \n \n ✓\n
\n\n «and so» no, motion will not be the same/no longer be SHM /\n \n \n OWTTE\n \n \n ✓\n
\n\n \n Show that the total kinetic energy\n \n E\n \n \n k\n \n of the sphere when it rolls, without slipping, at speed\n \n v\n \n is\n \n \n \n .\n \n
\n\n
\n\n [2]\n
\n\n \n \n E\n \n \n k\n \n =\n \n E\n \n \n k\n \n linear +\n \n E\n \n \n k\n \n rotational\n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n \n \n \n \n \n \n ✔\n \n \n
\n\n \n \n \n \n ✔\n \n
\n\n \n «\n \n \n \n »\n \n
\n\n
\n\n \n \n \n Answer is given in the question so check working is correct at each stage.\n \n \n \n
\n\n The derivation of the formula for the total kinetic energy of a rolling ball was well answered.\n
\n\n In the decay of polonium-210, alpha emission can be followed by the emission of a gamma photon.\n
\n\n State and explain whether the alpha particle or gamma photon will cause greater ionization in the surrounding material.\n
\n\n [2]\n
\n\n alpha particle ✓\n
\n\n is electrically charged hence more likely to interact with electrons «in the surrounding material» ✓\n
\n\n Many did not interpret the stem correctly and failed to compare the ionisation of alpha particles versus gamma rays.\n
\n\n A sample contains 5.0 g of pure polonium-210. The decay constant of polonium-210 is 5.8 × 10\n \n −8\n \n s\n \n −1\n \n . Lead-206 is stable.\n
\n\n Calculate the mass of lead-206 present in the sample after one year.\n
\n\n [3]\n
\n\n undecayed mass\n \n «\n \n g» ✓\n
\n\n mass of decayed polonium «\n \n undecayed mass»\n \n «g» ✓\n
\n\n mass of lead «\n \n »\n \n «g» ✓\n
\n\n
\n\n \n Allow\n \n [2] max\n \n for answers that ignore mass difference between Pb and Po (4.2 g).\n \n
\n\n \n Allow calculations in number of particles or moles for\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n Several answers referred incorrectly to electron energy levels. Successful candidates managed to score full marks, although it was also common to miss the relationship between energy and wavelength.\n
\n\n \n Which quantity has the fundamental SI units of kg m\n \n –1\n \n s\n \n –2\n \n ?\n
\n \n
\n \n A. Energy\n
\n B. Force\n
\n C. Momentum\n
\n D. Pressure\n \n
\n [1]\n
\n\n D\n
\n\n \n Calculate the average force exerted by the racquet on the ball.\n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n \n \n \n \n \n =\n \n \n \n 148 «N»≈150\n \n «N\n \n \n » ✔\n \n \n
\n\n
\n\n
\n\n At both HL and SL many candidates scored both marks for correctly answering this. A straightforward start to the paper. For those not gaining both marks it was possible to gain some credit for calculating either the change in momentum or the acceleration. At SL some used 64 ms-1 as a value for a and continued to use this value over the next few parts to the question.\n
\n\n State\n \n two\n \n properties of the products of nuclear fission due to which the spent nuclear fuel needs to be kept safe.\n
\n\n [2]\n
\n\n Have relatively short half-lives / high activity ✓\n
\n\n Their decay products are «usually» also radioactive ✓\n
\n\n Volatile / chemically active ✓\n
\n\n Biologically active / easily absorbed by living matter ✓\n
\n\n A mass of 0.25 kg hangs from a spring of spring constant 4.0 N m\n \n −1\n \n .\n
\n\n What is the natural frequency of oscillation for this system?\n
\n\n
\n A. 0.50 Hz\n
\n B. 0.64 Hz\n
\n\n C. 1.6 Hz\n
\n\n D. 2.0 Hz\n
\n\n [1]\n
\n\n B\n
\n\n The orbital period\n \n T\n \n of a moon orbiting a planet of mass\n \n M\n \n is given by\n
\n\n \n \n \n \n \n
\n\n where\n \n R\n \n is the average distance between the centre of the planet and the centre of the moon.\n
\n\n Show that\n \n \n \n \n \n
\n\n [3]\n
\n\n \n \n ALTERNATE 1\n \n \n
\n\n «using fundamental equations»\n
\n\n use of Universal gravitational force/acceleration/orbital velocity equations ✔\n
\n\n equating to centripetal force or acceleration. ✔\n
\n\n rearranges to get\n \n \n \n \n \n ✔\n
\n\n \n \n ALTERNATE 2\n \n \n
\n\n «starting with\n \n \n \n \n \n »\n \n \n
\n\n substitution of proper equation for T from orbital motion equations ✔\n
\n\n substitution of proper equation for M\n \n \n OR\n \n \n R from orbital motion equations ✔\n
\n\n rearranges to get\n \n \n \n \n \n ✔\n
\n\n This was another “show that” derivation. Many candidates attempted to work with universal gravitation equations, either from memory or the data booklet, to perform this derivation. The variety of correct solution paths was quite impressive, and many candidates who attempted this question were able to receive some marks. Candidates should be reminded on “show that” questions that it is never allowed to work backwards from the given answer. Some candidates also made up equations (such as T = 2𝝿r) to force the derivation to work out.\n
\n\n \n Draw a graph to show the variation with\n \n t\n \n of the horizontal speed\n \n v\n \n of the ball while it was in contact with the racket. Numbers are\n \n not\n \n required on the axes.\n \n
\n\n \n
\n [2]\n
\n\n \n
\n \n graph must show increasing speed from an initial of zero all the time ✔\n
\n overall correct curvature ✔\n \n
\n State the movement direction for which the geophone has its greatest sensitivity.\n
\n\n [1]\n
\n\n Vertical direction / parallel to springs ✓\n
\n\n Two positive and two negative charges are located at the corners of a square as shown. Point X is the centre of the square. What is the value of the electric field\n \n E\n \n and the electric potential\n \n V\n \n at X due to the four charges?\n
\n\n \n
\n \n
\n [1]\n
\n\n A\n
\n\n Candidates were unsure about this question with almost equal numbers choosing A and C. Electric potential is a scalar quantity so unaffected by the sign of the charge and can only be 0 in this arrangement removing the choice of C.\n
\n\n \n Suggest why de Broglie’s hypothesis is\n \n not\n \n consistent with Bohr’s conclusion that the electron’s orbit in the hydrogen atom has a well defined radius.\n \n
\n\n [2]\n
\n\n \n «de Broglie’s hypothesis states that the» electron is represented by a wave ✔\n
\n \n
\n \n therefore it cannot be localized/it is spread out/it does not have a definite position ✔\n \n
\n\n \n \n \n Award MP1 for any mention of wavelike property of an electron.\n \n \n \n
\n\n This question could have simply asked for the differences but did not puzzle the students who, when scoring, referred successfully to the differences between Bohr's postulate and de Broglie quantification of the wave like characteristics. Examiners marked this question without reference to particular physicist or what individuals suggested. As a result many scored the first mark for suggesting that electrons have wave like properties. The rest of the answers then commonly restated the stem of the question about a well-defined radius.\n
\n\n \n In the reference frame of the train a ball travels with speed 0.50\n \n c\n \n from the back to the front of the train, as the train passes the platform. Calculate the time taken for the ball to reach the front of the train in the reference frame of the train.\n \n
\n\n [1]\n
\n\n \n \n
\n \n
\n Because there were three frames of reference in this question many candidates struggled to find the simple value for the time of the ball’s travel down the train in the train’s frame of reference.\n
\n\n \n Satellite X is in orbit around the Earth. An identical satellite Y is in a higher orbit. What is correct for the total energy and the kinetic energy of the satellite Y compared with satellite X?\n \n
\n\n \n \n \n
\n [1]\n
\n\n B\n
\n\n We accept the comment from G2 forms that the wording of this question could be improved. The correct answer (B) considers the total and kinetic energies of satellite X the most popular answer.\n
\n\n \n Suggest, by reference to the graph, why it is unlikely that the relationship between\n \n T\n \n and\n \n v\n \n is linear.\n \n
\n\n [1]\n
\n\n \n a straight line cannot be drawn through all error bars\n
\n \n \n OR\n \n \n
\n the graph/line of best fit is /curved/not straight/parabolic etc.\n
\n \n \n OR\n \n \n
\n graph has increasing/variable gradient ✔\n \n
\n \n \n NOTE: Do not allow “a line cannot be drawn through all error bars” without specifying “straight”.\n \n \n
\n\n Explain the variation in intensity.\n
\n\n [3]\n
\n\n «incident and reflected» waves superpose/interfere/combine ✓\n
\n\n «that leads to» standing waves formed\n \n \n OR\n \n \n nodes and antinodes present ✓\n
\n\n at antinodes / maxima there is maximum intensity / constructive interference / «displacement» addition / louder sound ✓\n
\n\n at nodes / minima there is minimum intensity / destructive interference / «displacement» cancellation / quieter sound ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n \n Allow a sketch of a standing wave for\n \n MP2\n \n \n
\n\n \n Allow a correct reference to path or phase differences to identify constructive / destructive interference\n \n
\n\n ai) On most occasions it looked like students knew more than they could successfully communicate. Lots of answers talked about interference between the 2 waves, or standing waves being produced but did not go on to add detail. Candidates should take note of how many marks the question part is worth and attempt a structure of the answer that accounts for that. At SL there were problems recognizing a standard question requiring the typical explanation of how a standing wave is established.\n
\n\n 3aii) By far the most common answer was 2800 Hz, not doubling the value given to get the correct wavelength. That might suggest that some students misinterpreted adjacent minima as two troughs, therefore missing to use the information to correctly determine the wavelength as 0.24 m.\n
\n\n b) A question that turned out to be a good high level discriminator. Most candidates went for an answer that generally had everything at a lower intensity and didn't pick up on the relative amount of superposition. Those that did answer it very well, with very clear explanations, succeeded in recognizing that the nodes would be louder and the anti-nodes would be quieter than before.\n
\n\n Determine the time period of the system when\n \n is small.\n
\n\n [4]\n
\n\n attempted use of\n \n ✓\n
\n\n suitable read-offs leading to gradient of line = 28 « s\n \n -2\n \n » ✓\n
\n\n \n «\n \n » ✓\n
\n\n \n s ✓\n
\n\n This question was well done by many candidates. A common mistake was to select an incorrect gradient, but candidates who showed their work clearly still earned the majority of the marks.\n
\n\n Show that the internal resistance of the cell is about 0.7 Ω.\n
\n\n [2]\n
\n\n 29.4 (50.0 +\n \n r\n \n ) = 139 (10.0 +\n \n r\n \n ) ✓\n
\n\n
\n attempt to solve for\n \n r\n \n , e.g. 29.4 × 50.0 − 139 × 10.0 =\n \n r\n \n (139 − 29.4)\n
\n \n \n OR\n \n \n
\n\n 0.73 «Ω» ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow working backwards from 0.7 Ω.\n \n
\n\n Many answers here produced a number that did not round to 0.7 but students claimed it did. The simultaneous equation approach was seen in the best candidates, getting the right answer. It is worthy of reminding about the need of showing one more decimal place when calculating a show that value type of question.\n
\n\n Estimate the displacement needed to double the energy of the string.\n
\n\n [2]\n
\n\n use of\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n Show that the electric charge on the oil drop is given by\n
\n\n \n
\n\n where\n \n is the density of oil and\n \n is the volume of the oil drop.\n
\n\n [2]\n
\n\n Mass of drop is\n \n ✓\n
\n\n \n ✓\n
\n\n «hence answer»\n
\n\n
\n \n MP1 must be shown implicitly for credit.\n \n
\n There are 85 turns of wire in the loop. Calculate the maximum induced emf in the loop.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n maximum flux at «\n \n »\n \n «Wb» ✓\n
\n\n emf = «\n \n »\n \n «V» ✓\n
\n\n \n \n
\n ALTERNATIVE 2\n \n \n
\n emf induced in one turn =\n \n BvL\n \n =\n \n «V» ✓\n
\n\n emf\n \n «V» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n An electrical power supply has an internal resistance. It supplies a direct current\n \n to an external circuit for a time\n \n . What is the electromotive force (emf) of the power supply?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n An electron is accelerated from rest through a potential difference of 3.8 kV.\n
\n\n The de Broglie wavelength of the electron after acceleration is\n
\n\n
\n A. 0.021 mm\n
\n B. 0.021 μm\n
\n\n C. 0.021 nm\n
\n\n D. 0.021 pm\n
\n\n [1]\n
\n\n C\n
\n\n Describe the changes in gravitational potential energy of the oscillating system from\n \n t\n \n = 0 as it oscillates through one cycle of its motion.\n
\n\n [1]\n
\n\n maximum GPE at extremes, minimum in centre ✔\n
\n\n This straightforward question had surprisingly poorly answers. Candidate answers tended to be overly vague, such as “as the bob went higher the GPE increased and as it fell the GPE decreased.” Candidates needed to specify when GPE would be at maximum and minimum values. Some candidates mistakenly assumed that at t=0 the pendulum bob was at maximum height despite being told otherwise in the question stem.\n
\n\n White light is incident normally on separate diffraction gratings X and Y. Y has a greater number of lines per metre than X. Three statements about differences between X and Y are\n
\n\n I. adjacent slits in the gratings are further apart for X than for Y\n
\n II. the angle between red and blue light in a spectral order is greater in X than in Y\n
\n III. the total number of visible orders is greater for X than for Y.\n
\n Which statements are correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n Many candidates chose incorrect options. They need to be aware that there will usually be questions of this style and they need to practice them. The pattern of the answers is always the same and the best strategy is to try to identify a wrong answer which will then help to eliminate incorrect combinations.\n
\n\n The theoretical relationship assumes that the ball is only affected by the electric force.\n
\n\n Suggest why, in order to test the relationship, the length of the string should be much greater than the distance between the plates.\n
\n\n [2]\n
\n\n the angle between the string and the vertical should be very small «for any position of the ball» ✓\n
\n\n
\n\n so that the tension in the string is «almost» balanced by the ball’s weight\n
\n\n \n \n OR\n \n \n
\n\n restoring force from the string / horizontal component of tension negligibly small «compared with electric force» ✓\n
\n\n
\n\n \n OWTTE\n \n
\n\n State the movement direction for which the geophone has its greatest sensitivity.\n
\n\n [1]\n
\n\n Vertical direction / parallel to springs ✓\n
\n\n A block of mass 2.0 kg accelerates from a speed of 15 m s\n \n −1\n \n to a speed of 20 m s\n \n −1\n \n without changing its direction.\n
\n\n What impulse acts on the block?\n
\n\n
\n A. 2.5 N s\n
\n B. 5.0 N s\n
\n\n C. 10 N s\n
\n\n D. 17.5 N s\n
\n\n [1]\n
\n\n C\n
\n\n Calculate, in MeV, the energy released in this decay.\n
\n\n [2]\n
\n\n (\n \n m\n \n \n polonium\n \n −\n \n m\n \n \n lead\n \n −\n \n m\n \n α\n \n \n )\n \n c\n \n \n 2\n \n \n \n OR\n \n \n (209.93676 − 205.92945 − 4.00151)\n
\n\n \n \n OR\n \n \n
\n\n mass difference = 5.8 × 10\n \n −3\n \n ✓\n
\n\n
\n\n conversion to MeV using 931.5 to give 5.4 «MeV» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n .\n \n
\n\n \n Award\n \n [1]\n \n for 8.6 x 10\n \n −13\n \n J.\n \n
\n\n Generally, well answered. There were quite a few who fell into the trap of multiplying by an unnecessary c\n \n 2\n \n as they were not sure of the significance of the unit of u.\n
\n\n Determine the energy transferred to the air during the first 3.0 s of motion. State your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n «loss in» GPE = 3.4 × 10\n \n −5\n \n × 9.81 × 21 «= 7.0 × 10\n \n −3\n \n » «J»\n
\n\n \n \n OR\n \n \n
\n\n «gain in» KE = 0.5 × 3.4 × 10\n \n −5\n \n × 9.0\n \n 2\n \n «= 1.4 × 10\n \n −3\n \n » «J» ✓\n
\n\n
\n energy transferred to air «=7.0 × 10\n \n −3\n \n − 1.4 × 10\n \n −3\n \n » = 5.6 × 10\n \n −3\n \n » «J» ✓\n
\n
\n\n any calculated answer to 2 sf ✓\n
\n\n
\n\n \n Allow\n \n [1]\n \n through the use of kinematics assuming constant acceleration.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n Generally well answered, although several candidates lost a mark, usually as POT (power of ten) by quoting the value in kg leading to an answer of 5.3 J. Most candidates were able to score MP3 by rounding their calculation to two significant figures.\n
\n\n \n Outline,\n \n without\n \n calculation, how the internal resistance can be determined from this graph.\n \n
\n\n [2]\n
\n\n \n determine the gradient «of the line of best-fit» ✔\n
\n \n
\n \n \n r\n \n is the negative of this gradient ✔\n \n
\n\n Show that\n \n for the planets in a solar system where\n \n \n \n is the orbital period of a planet and\n \n \n \n is the radius of circular orbit of planet about its sun.\n
\n\n [2]\n
\n\n Equates centripetal force (with Newton’s law gravitation\n \n )\n
\n\n AND\n
\n\n \n ✓\n
\n\n leads to\n \n hence result ✓\n
\n\n Show that the phase difference between the oscillations of the two corks is\n \n radians.\n
\n\n [1]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n Phase difference is\n \n ×\n \n ✓\n
\n «=\n \n » ✓\n
\n \n ALTERNATIVE 2\n \n
\n\n One wavelength/period represents «phase difference» of 2\n \n and «corks» are ½ wavelength/period apart so phase difference is\n \n /\n \n \n OWTTE\n \n \n ✓\n
\n\n Determine the moment of inertia of the system about the central axis.\n
\n\n [2]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n 33 =\n \n × 4 ✓\n
\n\n
\n\n \n = 8.25 «kg m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (a)\n \n and\n \n (b)\n \n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n \n
\n\n \n Calculate, in m s\n \n –1\n \n , the speed for this wave.\n \n
\n\n [1]\n
\n\n \n v =\n \n \n «\n \n » 250 «m s\n \n –1\n \n »✔\n \n
\n\n Calculate the number of gas particles in the cylinder.\n
\n\n [2]\n
\n\n Correct conversion of T «T = 310 K» seen ✓\n
\n\n « use of =\n \n to get » 2.3 × 10\n \n 23\n \n ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n i.e., T in Celsius (Result is 2.7 x 10\n \n 24\n \n )\n \n
\n\n \n Allow use of n, R and N\n \n A\n \n \n
\n\n a) This was well answered with the majority converting to K. Quite a few found the number of moles but did not then convert to molecules.\n
\n\n bi) Well answered. It was pleasing to see how many recognised the need to state that the mass/number of molecules stayed the same as well as stating that the volume increased. At SL this recognition was less common so only 1 mark was often awarded.\n
\n\n bii) This was less successfully answered. A surprising number of candidates said that the internal energy of an ideal gas increases during an isothermal expansion. Many recognised that constant temp meant constant KE but then went on to state that the PE must increase and so the internal energy would increase.\n
\n
\n
\n Two long parallel wires P and Q are a distance\n \n d\n \n apart. They each carry a current.\n
\n\n A magnetic force per unit length\n \n acts on P due to Q.\n
\n\n The distance between the wires is increased to 2\n \n d\n \n and the current in Q is decreased to\n \n .\n
\n\n \n
\n What is the magnetic force per unit length that acts on P due to Q after the changes?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The frequency of the first harmonic in a pipe is measured. An adjustment is then made which causes the speed of sound in the pipe to increase. What is true for the frequency and the wavelength of the first harmonic when the speed of sound has increased?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n A turntable of mass\n \n \n \n and radius\n \n \n \n spins freely about the vertical axis at an initial angular velocity\n \n . The moment of inertia of the turntable about the axis of rotation is\n \n . A small body of mass\n \n \n \n is dropped close to the edge of the turntable with a negligible initial velocity.\n
\n\n \n
\n The body comes to rest relative to the turntable. What is the final angular velocity of the turntable?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n A pipe of length\n \n L\n \n is closed at one end. Another pipe is open at both ends and has length 2\n \n L\n \n . What is the lowest common frequency for the standing waves in the pipes?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Show that the tension\n \n T\n \n in the string is\n \n \n \n
\n\n [1]\n
\n\n use of\n \n T =\n \n \n \n \n \n MR\n \n \n \n \n to find\n \n T\n \n =\n \n \n \n \n MR ×\n \n \n \n \n ✔\n
\n\n «cancelling to show final answer»\n
\n\n This simple system of a solid cylinder rotating about a fixed axle and a block hanging on the rope accelerating proved to be rather difficult for many candidates. Only the best candidates were able to solve this problem, by writing two separate equations, and then solving to establish the acceleration of the system. The use of energy conservation was not a common technique attempted by students. As this is a “show that” question, candidates were asked to show that the angular acceleration is equal to g/(3R). Quite a high number of candidates successfully used the equations of motion and a similar number used the moment of inertia of the block around the axle. In ii), well-prepared candidates used the angular acceleration of the cylinder from i) and the tension expression to arrive at the given Mg/6.\n
\n\n \n A mass\n \n \n \n of water is at a temperature of 290 K. The specific heat capacity of water is\n \n \n \n . Ice, at its melting point, is added to the water to reduce the water temperature to the freezing point. The specific latent heat of fusion for ice is\n \n \n \n . What is the minimum mass of ice that is required?\n \n
\n\n \n A.\n \n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n \n D.\n \n \n
\n\n [1]\n
\n\n A\n
\n\n The mass of the charge\n \n q\n \n is 0.025 kg.\n
\n\n Calculate the angular frequency of the oscillations using the data in (a)(ii) and the expression in (b)(i).\n
\n\n [2]\n
\n\n \n ω\n \n =\n \n \n \n OR\n \n \n use of\n \n F\n \n =\n \n mω\n \n \n 2\n \n \n r\n \n OR\n \n F\n \n = 1.33\n \n x\n \n \n \n OR\n \n \n \n a\n \n = 53.3\n \n x\n \n ✓\n
\n\n «\n \n » = 7.299 «s\n \n −1\n \n »\n
\n\n The diagram shows the diffraction pattern for light passing through a single slit.\n
\n\n \n
\n What is\n
\n\n \n
\n\n A. 0.01\n
\n\n B. 0.02\n
\n\n C. 1\n
\n\n D. 2\n
\n\n [1]\n
\n\n A\n
\n\n Theory predicts that\n
\n\n \n
\n\n where\n \n and\n \n are constants. The fundamental units of\n \n are m\n \n 4\n \n and those of\n \n are kg m\n \n −1\n \n s\n \n −2\n \n .\n
\n\n Calculate\n \n and\n \n .\n
\n\n [2]\n
\n\n units of\n \n W\n \n : kg m s\n \n −2\n \n ✓\n
\n\n work leading to\n \n and\n \n ✓\n
\n\n The quantity\n \n is known as the Compton wavelength.\n
\n\n Show that the Compton wavelength is about 2.4 pm.\n
\n\n [1]\n
\n\n 2.43 pm ✓\n
\n\n \n The intensity of the light incident on the surface is reduced by half without changing the wavelength. Draw, on the graph, the variation of the current\n \n \n \n with potential\n \n \n \n after this change.\n \n
\n\n [2]\n
\n\n \n similar curve lower than original ✔\n
\n \n
\n \n with same horizontal intercept ✔\n \n
\n\n \n \n \n
\n the number of revolutions made by the rod until it stops rotating.\n
\n\n [2]\n
\n\n \n θ\n \n =\n \n = 27.0 rad ✓\n
\n\n \n N\n \n =\n \n = 4.3 ✓\n
\n\n The power supply to the pad has a negligible internal resistance.\n
\n\n State and explain the variation in current in the resistor as the temperature of the pad increases.\n
\n\n [2]\n
\n\n «Resistivity and hence» resistance will decrease ✓\n
\n\n «Pd across pad will not change because internal resistance is negligible»\n
\n Current will increase ✓\n
\n A bird of weight\n \n \n \n sits on a thin rope at its midpoint. The rope is almost horizontal and has negligible mass.\n
\n\n \n
\n The tension in the rope is\n
\n\n
\n A. less than\n \n
\n B. equal to\n \n
\n\n C. between\n \n and\n \n
\n\n D. greater than\n \n
\n\n [1]\n
\n\n D\n
\n\n Calculate the change in the entropy of the gas during the change A to B.\n
\n\n [1]\n
\n\n Δ\n \n S\n \n «=\n \n \n \n =\n \n \n \n »= 0.87 «JK\n \n −1\n \n » ✔\n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n Theory predicts that\n
\n\n \n
\n\n where\n \n and\n \n are constants. The fundamental units of\n \n are m\n \n 4\n \n and those of\n \n are kg m\n \n −1\n \n s\n \n −2\n \n .\n
\n\n Calculate\n \n and\n \n .\n
\n\n [2]\n
\n\n units of\n \n W\n \n : kg m s\n \n −2\n \n ✓\n
\n\n work leading to\n \n and\n \n ✓\n
\n\n The average temperature of the surface of a planet is five times greater than the average temperature of the surface of its moon. The emissivities of the planet and the moon are the same. The average intensity radiated by the planet is\n \n . What is the average intensity radiated by its moon?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Calculate:\n
\n\n
\n\n \n ✓\n
\n\n \n «rad s\n \n −2\n \n » ✓\n
\n\n Which process is the primary energy source in a red giant star?\n
\n\n
\n A. gravitational contraction\n
\n B. nuclear fusion of hydrogen in the core\n
\n\n C. nuclear fusion of helium in the core\n
\n\n D. nuclear fusion of helium in the shell surrounding the core\n
\n\n [1]\n
\n\n C\n
\n\n \n Define an\n \n inertial reference frame.\n \n \n
\n\n [1]\n
\n\n \n a coordinate system which is not accelerating/has constant velocity/Newtons 1st law applies ✔\n \n
\n\n \n \n OWTTE\n \n \n
\n\n \n \n Both “inertial” and “reference frame” need to be defined\n \n \n
\n\n In defining an inertial frame of reference far too many candidates started with the words ‘ a frame of reference that...... ’ instead of ‘a coordinate system that.....’\n
\n\n A ball falls with terminal velocity through air. What is correct about the kinetic energy and the total energy of the ball?\n
\n\n
\n| \n | \n\n \n Kinetic energy\n \n | \n\n \n Total energy\n \n \n | \n
| \n A.\n | \n\n constant\n | \n\n decreases\n | \n
| \n B.\n | \n\n increases\n | \n\n decreases\n | \n
| \n C.\n | \n\n constant\n | \n\n constant\n | \n
| \n D.\n | \n\n increases\n | \n\n constant\n | \n
\n
\n\n
\n\n A\n
\n\n A neutron is absorbed by a nucleus of uranium-235\n \n . One possible outcome is the production of two nuclides, barium-144\n \n and krypton-89\n \n .\n
\n\n How many neutrons are released in this reaction?\n
\n\n A. 0\n
\n\n B. 1\n
\n\n C. 2\n
\n\n D. 3\n
\n\n [1]\n
\n\n D\n
\n\n Answer C 2 neutrons, was the most popular choice suggesting that candidates failed to read the question properly and missed 'a neutron is adsorbed' at the beginning.\n
\n\n Two identical boxes are stored in a warehouse as shown in the diagram. Two forces acting on the top box and two forces acting on the bottom box are shown.\n
\n\n \n
\n Which is a force pair according to Newton’s third law?\n
\n\n A. 1 and 2\n
\n\n B. 3 and 4\n
\n\n C. 2 and 3\n
\n\n D. 2 and 4\n
\n\n [1]\n
\n\n C\n
\n\n The internal energy of a real gas is\n
\n\n
\n A. zero.\n
\n B. equal to the intermolecular potential energy of the particles.\n
\n\n C. equal to the total kinetic energy of the particles.\n
\n\n D. equal to the sum of the intermolecular potential energy and the total kinetic energy of the particles.\n
\n\n [1]\n
\n\n D\n
\n\n The polonium nucleus was stationary before the decay.\n
\n\n Show, by reference to the momentum of the particles, that the kinetic energy of the alpha particle is much greater than the kinetic energy of the lead nucleus.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n energy ratio expressed in terms of momentum, e.g.\n \n ✓\n
\n\n \n hence\n \n ✓\n
\n\n
\n\n \n «so\n \n has a much greater KE»\n
\n\n \n \n OR\n \n \n
\n\n \n «much» greater than\n \n «so\n \n has a much greater KE» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n alpha particle and lead particle have equal and opposite momenta ✓\n
\n\n so their velocities are inversely proportional to mass ✓\n
\n\n but KE ∝\n \n v\n \n \n 2\n \n «so\n \n has a much greater KE» ✓\n
\n\n Those who answered using the mass often did not get MP3 whereas those who converted to the number of particles or moles before the first calculation did, although that could be considered an unnecessary complication.\n
\n\n Deduce whether this collision is elastic.\n
\n\n [2]\n
\n\n Total angle between stones is 38°, angle will be 90° when elastic\n
\n\n \n OR\n \n
\n\n Compares kinetic energies in a correct calculation (initial ke = 53 J, final ke = 34 J +2.4 J) ✓\n
\n\n
\n Collision is not elastic ✓\n
\n State the phase difference between the waves at V and Y.\n
\n\n [1]\n
\n\n 0\n \n \n OR\n \n \n 2\n \n π\n \n \n \n OR\n \n \n 360°\n \n ✓\n \n
\n\n
\n\n Sketch, on the axes, a graph showing the variation with time of the vertical component of velocity\n \n v\n \n \n v\n \n of the ball until it reaches the table surface. Take\n \n g\n \n to be +10 m s\n \n −2\n \n .\n
\n\n \n
\n [2]\n
\n\n increasing straight line from zero up to 0.2 s in\n \n x\n \n -axis\n \n ✓\n \n
\n\n with gradient = 10\n \n ✓\n \n
\n\n Show that the\n \n is about 80.\n
\n\n [2]\n
\n\n \n \n \n AND\n \n \n \n \n \n seen\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n For\n \n MP1\n \n , potentials can be seen individually or as a ratio.\n \n
\n Draw the variation with time\n \n of the angular displacement\n \n of the bar during the acceleration.\n
\n\n \n
\n [1]\n
\n\n \n concave up from origin\n \n \n ✓\n \n
\n\n \n
\n A tram is just leaving the lower railway station.\n
\n\n Determine, as the train leaves the lower station,\n
\n\n
\n\n Resistance of cable = 0.072 Ω ✓\n
\n\n Pd is (500 − 0.072 × 600) = 457 V ✓\n
\n\n Estimate, using the spacetime diagram, the time in seconds when the flash of light reaches the spaceship according to the Earth observer.\n
\n\n [2]\n
\n\n Line drawn at 45° from\n \n ct\n \n = 2 km to hit spaceship world line at\n \n ct\n \n = 5 km\n
\n\n \n \n OR\n \n \n
\n\n \n ct\n \n = 1.2/(\n \n c\n \n − 0.6\n \n c\n \n ) + 2 = 5 «km» ✓\n
\n\n \n t\n \n =\n \n = 1.7 × 10\n \n −5\n \n «s» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for\n \n BCA\n \n \n
\n\n A gas undergoes one cycle of a cyclic process.\n
\n\n The net change in internal energy of the gas is\n
\n\n
\n A. zero.\n
\n B. positive.\n
\n\n C. negative.\n
\n\n D. determined by the initial temperature of the gas.\n
\n\n [1]\n
\n\n A\n
\n\n Show that each resistor has a resistance of about 30 Ω.\n
\n\n [1]\n
\n\n \n «Ω»\n \n ✓\n \n
\n\n \n Must see either the substituted values\n \n OR\n \n a value for R to at least three s.f.\n \n
\n\n
\n\n \n Three observations of the behaviour of electrons are\n \n
\n\n \n I. electron emission as a result of the photoelectric effect\n
\n II. electron diffraction as an electron interacts with an atom\n
\n III. emission of radio waves as a result of electrons oscillating in a conductor.\n \n
\n \n Which observations are evidence that the electron behaves as a particle?\n \n
\n\n
\n\n \n A. I and II only\n
\n \n
\n \n B. I and III only\n
\n \n
\n \n C. II and III only\n
\n \n
\n \n D. I, II and III\n \n
\n\n [1]\n
\n\n B\n
\n\n \n Two flasks P and Q contain an ideal gas and are connected with a tube of negligible volume compared to that of the flasks. The volume of P is twice the volume of Q.\n \n
\n\n \n \n \n
\n \n \n P is held at a temperature of 200 K and Q is held at a temperature of 400 K.\n \n \n
\n\n \n \n What is mass of\n \n ?\n \n \n
\n\n
\n\n \n \n A.\n \n \n \n
\n\n \n \n B.\n \n \n \n
\n\n \n \n C. 4\n \n \n
\n\n \n \n D. 8\n \n \n
\n\n [1]\n
\n\n C\n
\n\n The sample begins to freeze during the thermal energy transfer. Explain, in terms of the molecular model of matter, why the temperature of the sample remains constant during freezing.\n
\n\n [3]\n
\n\n \n «intermolecular» bonds are formed during freezing\n \n \n ✓\n \n
\n\n \n
\n bond-forming process releases energy\n
\n \n \n \n \n OR\n \n \n
\n \n \n «\n \n \n intermolecular\n \n \n »\n \n \n PE decreases\n \n \n «\n \n \n and the difference is transferred as heat\n \n \n »\n \n \n ✓\n \n
\n \n
\n \n \n «\n \n \n average random\n \n \n »\n \n \n KE of the molecules does not decrease/change\n \n \n ✓\n \n
\n \n
\n \n \n temperature is related to «average» KE of the molecules «hence unchanged»\n \n \n ✓\n \n
\n
\n\n \n \n To award MP3 or MP4 molecules/particles/atoms must be mentioned.\n \n \n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n A block of mass 2.0 kg is placed on a trolley of mass 5.0 kg, moving horizontally. A force of 8.0 N is applied to the block which slides on the surface of the trolley. The frictional force between the trolley and the ground is zero.\n
\n\n \n
\n The trolley accelerates at a rate of 1.0 m s\n \n −2\n \n . What is the coefficient of dynamic friction between the block and the trolley?\n
\n\n
\n A. 0.05\n
\n B. 0.15\n
\n\n C. 0.25\n
\n\n D. 0.35\n
\n\n [1]\n
\n\n C\n
\n\n What is the sequence for the evolution of a main sequence star of about 2 solar masses?\n
\n\n
\n A. Red super giant → supernova → neutron star\n
\n B. Red giant → planetary nebula → white dwarf\n
\n\n C. Red giant → supernova → white dwarf\n
\n\n D. Red super giant → planetary nebula → neutron star\n
\n\n [1]\n
\n\n B\n
\n\n mass number.\n
\n\n [1]\n
\n\n 3 ✓\n
\n\n \n A coil is rotated in a uniform magnetic field. An alternating emf is induced in the coil. What is a possible phase relationship between the magnetic flux through the coil and the induced emf in the coil when the variations of both quantities are plotted with time?\n \n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Two satellites W and X have the same mass. They have circular orbits around the same planet. W is closer to the surface than X. What quantity is smaller for W than for X?\n
\n\n A. Gravitational force from the planet\n
\n\n B. Angular velocity\n
\n\n C. Orbital speed\n
\n\n D. Orbital period\n
\n\n [1]\n
\n\n D\n
\n\n Explain why the magnitude of the force exerted on the mass by the rod is not constant.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n the net/centripetal force has constant magnitude ✓\n
\n\n the direction of the net/centripetal force constantly changes ✓\n
\n\n this is achieved by vector-adding weight and the force from the rod\n
\n\n \n \n OR\n \n \n
\n\n the force from the rod is vector difference of the centripetal force and weight ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n at the top F\n \n rod\n \n = F\n \n c\n \n − W ✓\n
\n\n at the bottom, F\n \n rod\n \n = F\n \n c\n \n + W ✓\n
\n\n net F/F\n \n c\n \n is constant so the force from the rod is different «hence is changing» ✓\n
\n\n
\n\n \n Accept reference to centripetal or net force indistinctly.\n \n
\n\n \n Allow reference to centripetal acceleration.\n \n
\n\n Many got into a bit of a mess with this one and it was quite difficult to interpret some of the answers. If they started out with the net/centripetal force being constant, then it was often easy to follow the reasoning. Starting with force on the rod varying often led to confusion. Quite a few did not pick up on the constant speed vertical circle so there were complicated energy/speed arguments to pick through.\n
\n\n A solid metallic sphere is positively charged and isolated from all other charges.\n
\n\n The electric potential due to the sphere\n
\n\n
\n A. is constant inside the sphere.\n
\n B. is constant outside the sphere.\n
\n\n C. is smallest at the surface of the sphere.\n
\n\n D. increases with distance from the sphere.\n
\n\n [1]\n
\n\n A\n
\n\n Show that the surface temperature of\n \n δ\n \n Vel A is about 9000 K.\n
\n\n [1]\n
\n\n correct substitution into\n \n OR 9350 K ✓\n
\n\n A car has an initial speed of 16 m s\n \n −1\n \n . It decelerates at 4.0 m s\n \n −2\n \n until it stops.\n
\n\n What is the distance travelled by the car?\n
\n\n
\n A. 4 m\n
\n B. 16 m\n
\n\n C. 32 m\n
\n\n D. 64 m\n
\n\n [1]\n
\n\n C\n
\n\n State and explain the magnitude of the force on a length of 0.50 m of wire Q due to the current in P.\n
\n\n [2]\n
\n\n From Newton’s third law, the force on a length of Q is equal but opposite to the force on the same length of P ✓\n
\n\n \n ✓\n
\n\n \n T\n \n \n b\n \n >\n \n T\n \n \n t\n \n
\n\n [2]\n
\n\n Convection identified ✓\n
\n\n energy transfer through movement of bodies of liquid at different densities ✓\n
\n\n Show that the average rate at which thermal energy is transferred into the chocolate is about 15 W.\n
\n\n [3]\n
\n\n Reads change in temperature to be 45 − 31\n \n \n OR\n \n \n 14 °C ✓\n
\n\n
\n \n Q\n \n = 0.082 × 1.6 × 10\n \n 3\n \n × 14 = 1.84 × 10\n \n 3\n \n «J» ✓\n
\n \n P\n \n =\n \n = 15.3\n \n 15 «W»✓\n
\n\n
\n\n \n Must see either full substitution\n \n OR\n \n answer to at least 3 s.f. in\n \n MP3\n \n \n
\n\n The moment of inertia of the rod about the axis is 0.180 kg m\n \n 2\n \n . Show that the moment of inertia of the rod–particle system is about 0.25 kg m\n \n 2\n \n .\n
\n\n [1]\n
\n\n 0.180 + 0.200 × 0.60\n \n 2\n \n «= 0.252 kg m\n \n 2\n \n » ✓\n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n The angle between the clay–air surface and\n \n path 1\n \n is 80°.\n
\n\n Draw, on the diagram, the subsequent path of a sound wave that travels initially in the clay along\n \n path 1\n \n .\n
\n\n [2]\n
\n\n ray shown reflected back into the clay (and then to Z) at (by eye) the incidence angle ✓\n
\n\n ray shown refracted into the sandstone with angle of refraction greater than angle of incidence (by eye) ✓\n
\n\n Two surfaces X and Y emit radiation of the same surface intensity. X emits a radiation of peak wavelength twice that of Y.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 2\n
\n\n D. 16\n
\n\n [1]\n
\n\n D\n
\n\n Explain, by reference to Faraday’s law of induction, how an electromotive force (emf) is induced in the coil.\n
\n\n [3]\n
\n\n \n there is a magnetic flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n in the coil / coil cuts magnetic field\n \n \n ✓\n \n
\n\n \n this flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n changes as the angle varies/coil rotates\n \n \n ✓\n \n
\n\n \n «\n \n \n Faraday’s law\n \n \n »\n \n \n connects induced emf with rate of change of flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n with time\n \n \n ✓\n \n
\n\n \n \n
\n Do not award MP2 or 3 for answers that don’t discuss flux.\n \n \n
\n This question was well answered with the majority discussing changes in flux rather than wires cutting field lines, which was good to see.\n
\n\n A cylindrical metal rod has a temperature difference between its ends and is in a steady state. The rate of energy transfer along the rod is\n \n \n \n . No energy is transferred from the curved side of the rod.\n
\n\n The rod is changed for one made from the same material but with double the length and double the diameter. The temperature difference is halved. The rate of energy transfer in the rod is now\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Sketch, on the\n \n pV\n \n diagram, the remaining two processes BC and CA that the gas undergoes.\n
\n\n [2]\n
\n\n concave curved line from B to locate C with a higher pressure than A ✓\n
\n\n vertical line joining C to A ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n i.e.,\n \n award [1]\n \n for first process locating C at a lower pressure than A, then vertical line to A.\n \n
\n\n \n Arrows on the processes are not needed.\n \n
\n\n \n Point C need not be labelled.\n \n
\n\n \n
\n Show that the angular speed of the system immediately after the collision is about 5.7 rad s\n \n −1\n \n .\n
\n\n [2]\n
\n\n angular speed of particle = «12/0.6 = » 20 «rad s\n \n −1\n \n »\n
\n\n \n \n OR\n \n \n
\n\n angular momentum of particle «0.200 × 12.0 × 0.60» = 1.44 «Js» ✓\n
\n\n
\n «angular momentum of rod-particle system 0.252\n \n ω\n \n »\n
\n equating\n \n ω\n \n = «\n \n » = 5.71 rad s\n \n −1\n \n ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , working or answer to at least 3 SF should be seen.\n \n
\n\n Calculate the largest fractional uncertainty in\n \n T\n \n for these data.\n
\n\n [2]\n
\n\n \n T\n \n = 0.5 s ✓\n
\n\n «\n \n » 0.2 ✓\n
\n\n A satellite in a circular orbit around the Earth needs to reduce its orbital radius.\n
\n\n What is the work done by the satellite rocket engine and the change in kinetic energy resulting from this shift in orbital height?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n This question was generally well answered, however a significant number of students (incorrectly) selected response A suggesting a lack of clarity around the work done as a result of changes in orbital height.\n
\n\n Calculate, for the cylinder, at the instant just before the block hits the ground the kinetic energy.\n
\n\n [2]\n
\n\n \n ω\n \n =<\n \n \n \n Δ\n \n t =\n \n \n \n \n \n Δt =\n \n \n \n \n \n \n = > 8.99 «rads\n \n −1\n \n » ✔\n
\n\n \n E\n \n \n k\n \n = «\n \n \n \n \n Iω\n \n \n 2\n \n \n =\n \n \n \n \n \n MR\n \n \n 2\n \n \n ω\n \n 2\n \n \n =\n \n \n \n \n \n × 12 × 0.20\n \n 2\n \n × 8.99\n \n 2\n \n = » 9.7 «J»\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n Angular speed, angular momentum and the kinetic energy of the cylinder at the instant given were successfully calculated by only the better-prepared candidates. Students were mostly able to recognize the correct expressions to use but struggled to find the angular speed in many instances. Error carried forward was very common throughout this question for students who incorrectly determined the angular velocity but understood and correctly applied the momentum and energy equations. In ii), quite a high number of candidates misread the question and calculated the energy of the whole system.\n
\n\n \n A ball is thrown vertically upwards. Air resistance is negligible. What is the variation with time\n \n t\n \n of the kinetic energy\n \n E\n \n \n k\n \n of the ball?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n Determine\n \n A\n \n by drawing the line of best fit.\n
\n\n [3]\n
\n\n a best-fit line drawn through the entire range of the data ✓\n
\n\n large triangle greater than half a line or two data points on the line greater than half a line apart ✓\n
\n\n correct read offs consistent with the line,\n \n eg\n \n \n ✓\n
\n\n \n Accept answer in the range 3.8–4.2\n \n
\n\n Calculate the distance between star A and star B relative to observer P.\n
\n\n [2]\n
\n\n \n = 1.6 ✓\n
\n\n \n D\n \n =\n \n = 3 «ly» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n An object of mass\n \n m\n \n is sliding down a ramp at constant speed. During the motion it travels a distance\n \n \n \n along the ramp and falls through a vertical distance\n \n h\n \n . The coefficient of dynamic friction between the ramp and the object is\n \n μ\n \n . What is the total energy transferred into thermal energy when the object travels distance\n \n \n \n ?\n
\n\n
\n\n \n
\n A.\n \n mgh\n \n
\n\n B.\n \n mgx\n \n
\n\n C.\n \n μmgh\n \n
\n\n D.\n \n μmgx\n \n
\n\n [1]\n
\n\n A\n
\n\n the angular velocity of the ring after a time of 5.0 s.\n
\n\n [1]\n
\n\n \n «rad s\n \n −1\n \n » ✓\n
\n\n State and explain the reference frame in which the proper time for shuttle S to journey from star A to star B can be measured.\n
\n\n [2]\n
\n\n shuttle measures proper time ✓\n
\n\n as the events occur at the same place for the shuttle / shuttle is at both events ✓\n
\n\n The energy levels of an atom are shown. How many photons of energy\n \n greater\n \n than 1.9 eV can be emitted by this atom?\n
\n\n \n
\n
\n A. 1\n
\n B. 2\n
\n\n C. 3\n
\n\n D. 4\n
\n\n [1]\n
\n\n D\n
\n\n Which is the definition of gravitational field strength at a point?\n
\n\n A. The sum of the gravitational fields created by all masses around the point\n
\n\n B. The gravitational force per unit mass experienced by a small point mass at that point\n
\n\n C.\n \n , where\n \n \n \n is the mass of a planet and\n \n \n \n is the distance from the planet to the point\n
\n\n D. The resultant force of gravitational attraction on a mass at that point\n
\n\n [1]\n
\n\n B\n
\n\n \n A student measures the radius\n \n R\n \n of a circular plate to determine its area. The absolute uncertainty in\n \n R\n \n is Δ\n \n R\n \n .\n \n
\n\n \n What is the\n \n fractional\n \n uncertainty in the area of the plate?\n \n
\n\n \n A.\n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n
\n\n
\n\n [1]\n
\n\n A\n
\n\n State the principal energy change in nuclear fission.\n
\n\n [1]\n
\n\n Mass-energy «of uranium» into kinetic energy of fission products ✓\n
\n\n A planet has an albedo of 0.30. A simplified energy balance for the planet is shown.\n
\n\n \n
\n What is the intensity radiated by the surface of the planet?\n
\n\n
\n A. 70 W m\n \n −2\n \n
\n B. 90 W m\n \n −2\n \n
\n\n C. 100 W m\n \n −2\n \n
\n\n D. 130 W m\n \n −2\n \n
\n\n [1]\n
\n\n D\n
\n\n Calculate the temperature at Y.\n
\n\n [3]\n
\n\n idea that\n \n is same in both bars because lagged ✓\n
\n\n work to show that\n \n
\n \n \n OR\n \n \n
\n Temperature difference across XY is twice temperature difference across YZ ✓\n
\n solves to show that\n \n ✓\n
\n\n magnetic force on section AB of the loop.\n
\n\n [1]\n
\n\n Repulsive / to the right ✓\n
\n\n The graphs show the variation with time of the activity and the number of remaining nuclei for a sample of a radioactive nuclide.\n
\n\n \n
\n What is the decay constant of the nuclide?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Used fuel rods are stored in water after removal from a nuclear reactor.\n
\n\n The reason for this is that the water\n
\n\n
\n A. absorbs the gamma radiation which is emitted by the used fuel\n
\n B. cools the used fuel which is still transferring energy\n
\n\n C. boils to steam which can then rotate a turbine\n
\n\n D. reacts chemically with the fuel which reduces the activity\n
\n\n [1]\n
\n\n B\n
\n\n The gravitational field strength at the surface of the Earth is often taken to be 9.8 N kg\n \n −1\n \n .\n
\n\n The use of this value to calculate the weight of an object\n \n above\n \n the surface of the Earth is\n
\n\n
\n A. a paradigm shift in our understanding of gravity.\n
\n B. an attempt to model gravitational fields.\n
\n\n C. an outcome from a peer review.\n
\n\n D. an approximation used for estimation purposes.\n
\n\n [1]\n
\n\n D\n
\n\n Explain why the received intensity varies between maximum and minimum values.\n
\n\n [3]\n
\n\n movement of B means that path distance is different « between BM and AM »\n
\n \n \n OR\n \n \n
\n movement of B creates a path difference «between BM and AM» ✓\n
\n interference\n
\n \n \n OR\n \n \n
\n superposition «of waves» ✓\n
\n maximum when waves arrive in phase / path difference = n x lambda\n
\n \n \n OR\n \n \n
\n minimum when waves arrive «180° or\n \n » out of phase / path difference = (n+½) x lambda ✓\n
\n This was an \"explain\" questions, so examiners were looking for a clear discussion of the movement of speaker B creating a changing path difference between B and the microphone and A and the microphone. This path difference would lead to interference, and the examiners were looking for a connection between specific phase differences or path differences for maxima or minima. Some candidates were able to discuss basic concepts of interference (e.g. \"there is constructive and destructive interference\"), but failed to make clear connections between the physical situation and the given graph. A very common mistake candidates made was to think the question was about intensity and to therefore describe the decrease in peak height of the maxima on the graph. Another common mistake was to approach this as a Doppler question and to attempt to answer it based on the frequency difference of B.\n
\n\n Estimate, in W, the average rate at which energy is transferred by the decay of magnesium-27 during the 10.0 minutes after the irradiation ends.\n
\n\n [2]\n
\n\n Total energy released = ans\n \n (c)(ii)\n \n × 2.62 × 10\n \n 6\n \n × 1.6 × 10\n \n −19\n \n «= 2100 J» ✓\n
\n\n «\n \n =» 3.4 −3.5 «W» ✓\n
\n\n Monochromatic light is incident on two very narrow slits. The light that passes through the slits is observed on a screen. M is directly opposite the midpoint of the slits.\n \n represents the displacement from M in the direction shown.\n
\n\n \n
\n A student argues that what will be observed on the screen will be a total of two bright spots opposite the slits. Explain why the student’s argument is incorrect.\n
\n\n [2]\n
\n\n light acts as a wave «and not a particle in this situation» ✓\n
\n\n light at slits will diffract / create a diffraction pattern ✓\n
\n\n light passing through slits will interfere / create an interference pattern «creating bright and dark spots» ✓\n
\n\n A nucleus of platinum (Pt) undergoes alpha decay to form an osmium (Os) nucleus as represented by the following reaction.\n
\n\n \n → Os + alpha particle\n
\n\n What are the number of protons and the number of neutrons in the osmium nucleus?\n
\n\n
\n| \n | \n\n \n Number of protons\n \n | \n\n \n Number of neutrons\n \n | \n
| \n A.\n | \n\n 74\n | \n\n 93\n | \n
| \n B.\n | \n\n 76\n | \n\n 93\n | \n
| \n C.\n | \n\n 74\n | \n\n 95\n | \n
| \n D.\n | \n\n 76\n | \n\n 95\n | \n
\n
\n\n
\n\n [1]\n
\n\n D\n
\n\n A piece of metal at a temperature of\n \n is dropped into an equal mass of water at a temperature of\n \n in a container of negligible mass. The specific heat capacity of water is four times that of the metal. What is the final temperature of the mixture?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The mass of Mars is about ten times that of the Moon. The radius of Mars is about twice that of the Moon.\n
\n\n What is the\n \n ?\n
\n\n
\n A.\n \n
\n B. 2\n \n
\n\n C. 5\n
\n\n D. 25\n
\n\n [1]\n
\n\n A\n
\n\n Loudspeaker A is switched off. Loudspeaker B moves away from M at a speed of 1.5 m s\n \n −1\n \n while emitting a frequency of 3.0 kHz.\n
\n\n Determine the difference between the frequency detected at M and that emitted by B.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n use of\n \n (+ sign must be seen)\n \n \n OR\n \n \n \n = 2987 «Hz» ✓\n
\n «\n \n » = 13 «Hz» ✓\n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n Attempted use of\n \n ≈\n \n
\n
\n « Δf » = 13 «Hz» ✓\n
\n Many candidates were successful in setting up a Doppler calculation and determining the new frequency, although some missed the second step of finding the difference in frequencies.\n
\n\n Show that the average rate at which thermal energy is transferred into the chocolate is about 15 W.\n
\n\n [3]\n
\n\n Reads change in temperature to be 45 − 31\n \n \n OR\n \n \n 14 °C ✓\n
\n\n
\n \n Q\n \n = 0.082 × 1.6 × 10\n \n 3\n \n × 14 = 1.84 × 10\n \n 3\n \n «J» ✓\n
\n \n P\n \n =\n \n = 15.3\n \n 15 «W»✓\n
\n\n
\n\n \n Must see either full substitution\n \n OR\n \n answer to at least 3 s.f. in\n \n MP3\n \n \n
\n\n Explain why the intensity of light at\n \n = 0 is 4\n \n .\n
\n\n [2]\n
\n\n The amplitude «at\n \n x\n \n = 0» will be doubled ✓\n
\n\n intensity is proportional to amplitude squared /\n \n ∝\n \n A\n \n \n 2\n \n ✓\n
\n\n Monochromatic light is incident on a single slit to form a diffraction pattern on a screen. The width of the single slit is then halved.\n
\n\n What are the change in the width of the central maximum and the change in the maximum intensity of the pattern?\n
\n\n
\n| \n | \n\n \n Change in width of central maximum\n \n | \n\n \n Change in maximum intensity of pattern\n \n | \n
| \n A.\n | \n\n decrease\n | \n\n increase\n | \n
| \n B.\n | \n\n decrease\n | \n\n decrease\n | \n
| \n C.\n | \n\n increase\n | \n\n decrease\n | \n
| \n D.\n | \n\n increase\n | \n\n increase\n | \n
\n
\n\n [1]\n
\n\n C\n
\n\n Four identical resistors, each of resistance\n \n , are connected as shown.\n
\n\n \n
\n What is the effective resistance between P and Q?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Two identical boxes containing different masses are sliding with the same initial speed on the same horizontal surface. They both come to rest under the influence of the frictional force of the surface. How do the frictional force and acceleration of the boxes compare?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Draw an arrow on the diagram to represent the direction of the acceleration of the satellite.\n
\n\n [1]\n
\n\n arrow normal to the orbit towards the Earth ✓\n
\n\n An electric field is established between two electrodes separated by distance\n \n d\n \n , held at a potential difference of\n \n V\n \n . A charged particle in this field experiences a force\n \n F\n \n .\n
\n\n \n
\n What is the charge on the particle?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Discuss how the mean kinetic energy of the argon atoms in the mixture compares with that of the helium atoms.\n
\n\n [2]\n
\n\n the gases are in the same container at the same temperature so are\n \n in equilibrium\n \n ✓\n
\n\n they must have the same mean/average kinetic energy ✓\n
\n\n the ideal gas law,\n
\n\n [1]\n
\n\n it is the temperature at which the volume\n
\n\n \n \n OR\n \n \n
\n\n the pressure extrapolates to zero (can be shown by sketch) ✓\n
\n\n Calculate the resistance of R.\n
\n\n [2]\n
\n\n Current in R is «(0.45 − 0.4)=» 0.05 A ✓\n
\n\n So resistance is «\n \n » = 28 «Ω»\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n a(i)\n \n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n The maximum height reached by the bottle is greater with an air–water mixture than with only high-pressure air in the bottle.\n
\n\n Assume that the speed at which the propellant leaves the bottle is the same in both cases.\n
\n\n Explain why the bottle reaches a greater maximum height with an air–water mixture.\n
\n\n [2]\n
\n\n Mass «leaving the bottle per second» will be larger for air–water ✓\n
\n\n the momentum change/force is greater ✓\n
\n\n \n Allow opposite argument for air only\n \n
\n\n On approaching a stationary observer, a train sounds its horn and decelerates at a constant rate. At time\n \n t\n \n the train passes by the observer and continues to decelerate at the same rate. Which diagram shows the variation with time of the frequency of the sound measured by the observer?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n State the vertical component of the total momentum of the balls after the collision.\n
\n\n [1]\n
\n\n Zero ✓\n
\n\n Discuss the ratios in (a) and (c).\n
\n\n [2]\n
\n\n the answers are the same ✓\n
\n\n count rates cannot vary from frame to frame /\n \n \n OWTTE\n \n \n ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from\n \n (c)\n \n .\n \n
\n\n \n \n Award [2]\n \n for “count rates cannot vary” if student made a mistake\n \n OR\n \n no answer in\n \n (c)\n \n and well discussed here.\n \n
\n\n State why the experiment is repeated with different values of\n \n .\n
\n\n [1]\n
\n\n \n In order to draw a graph « of\n \n \n \n \n \n versus\n \n »\n
\n \n \n \n \n OR\n \n \n
\n \n
\n \n to confirm proportionality between «\n \n \n \n \n \n and\n \n \n \n »\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n to confirm relationship between «\n \n \n \n \n \n and\n \n \n \n »\n
\n \n
\n \n \n \n OR\n \n \n \n \n
\n \n
\n \n because\n \n \n W\n \n \n is the independent variable in the experiment\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Most candidates scored. Different wording was used to express the aim of confirming the relationship.\n
\n\n Show that the rotational kinetic energy of the turbine decreases at a constant rate.\n
\n\n [3]\n
\n\n Rotational KE is proportional to\n \n ✓\n
\n\n Calculation of\n \n for at least four points, e.g. {96.1, 76.7, 57.6, 38.4, 19.3}×10\n \n 3\n \n
\n\n Shows that the differences in equal time intervals are approximately the same, e.g. {19.4, 19.1, 19.2, 19.1, 19.3}×10\n \n 3\n \n ✓\n
\n\n
\n\n \n Allow a tolerance of ±1×10\n \n 3\n \n s\n \n −2\n \n from the values stated in MP2.\n \n
\n\n A ball is projected at an angle to the horizonal on Earth reaching a maximum height\n \n H\n \n and a maximum range\n \n R\n \n . The same ball is projected at the same angle and speed on a planet where the acceleration due to gravity is three times that on Earth. Resistance effects are negligible.\n
\n\n What is the maximum range and the maximum height reached on that planet?\n
\n\n
\n| \n | \n\n \n Maximum range\n \n | \n\n \n Maximum height\n \n \n \n reached\n \n | \n
| \n A.\n | \n\n \n | \n\n \n | \n
| \n B.\n | \n\n \n | \n\n \n | \n
| \n C.\n | \n\n \n | \n\n \n | \n
| \n D.\n | \n\n \n | \n\n \n | \n
\n
\n\n [1]\n
\n\n A\n
\n\n State\n \n two\n \n assumptions of the kinetic model of an ideal gas that refer to intermolecular collisions.\n
\n\n [2]\n
\n\n The collisions are elastic ✓\n
\n\n The time for a collision is much shorter than the time between collisions ✓\n
\n\n The intermolecular forces are only present during collisions ✓\n
\n\n Light with photons of energy 8.0 × 10\n \n −20\n \n J are incident on a metal surface in a photoelectric experiment.\n
\n\n \n
\n The work function of the metal surface is 4.8 × 10\n \n −20\n \n J . What minimum voltage is required for the ammeter reading to fall to zero?\n
\n\n A. 0.2 V\n
\n\n B. 0.3 V\n
\n\n C. 0.5 V\n
\n\n D. 0.8 V\n
\n\n [1]\n
\n\n A\n
\n\n Options B and C were both effective distractors in this photoelectric effect question. There was a heightened number of blanks (no response) relative to the questions immediately before and after, and the low difficulty index suggests that candidates found this question challenging.\n
\n\n A car travels clockwise around a circular track of radius\n \n R\n \n . What is the magnitude of displacement from X to Y?\n
\n\n \n
\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n The variation of\n \n d\n \n with\n \n W\n \n is shown.\n
\n\n \n
\n Outline\n \n one\n \n experimental reason why the graph does not go through the origin.\n
\n\n [1]\n
\n\n beam bends under its own weight / weight of pan\n
\n\n \n \n OR\n \n \n
\n\n specified systematic error in\n \n d\n \n ✓\n
\n\n The table gives data relating to the two moons of Mars.\n
\n\n
\n| \n Moon\n | \n\n \n T\n \n / hour\n | \n\n \n r\n \n / Mm\n | \n
| \n Phobos\n | \n\n 7.66\n | \n\n 9.38\n | \n
| \n Deimos\n | \n\n 30.4\n | \n\n -\n | \n
\n
\n\n Determine\n \n r\n \n for Deimos.\n
\n\n [2]\n
\n\n \n seen or correct substitution ✓\n
\n\n 23.5 Mm ✓\n
\n\n Explain, by reference to the second law of thermodynamics, why a real engine operating between the temperatures of 620 K and 340 K cannot have an efficiency greater than the answer to (b)(i).\n
\n\n [2]\n
\n\n the Carnot cycle has the maximum efficiency «for heat engines operating between two given temperatures »✔\n
\n\n real engine can not work at Carnot cycle/ideal cycle ✔\n
\n\n the second law of thermodynamics says that it is impossible to convert all the input heat into mechanical work ✔\n
\n\n a real engine would have additional losses due to friction\n \n etc\n \n ✔\n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n State the\n \n speed\n \n of the flash of light according to an observer on the ground using Galilean relativity.\n
\n\n [1]\n
\n\n \n c–v\n \n ✔\n
\n\n The speed of a flash of light from different viewpoints. Most of the prepared candidates well stated the speed of the flash using Galilean relativity, Maxwell’s theory and Einstein’s theory.\n
\n\n The gravitational field strength at the surface of a planet of radius\n \n R\n \n is\n \n . A satellite is moving in a circular orbit a distance\n \n R\n \n above the surface of the planet. What is the magnitude of the acceleration of the satellite?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Determine the wavelength of the incident photon.\n
\n\n [2]\n
\n\n Energy of incident photon =«\n \n »\n \n «eV» ✓\n
\n\n Wavelength of incident photon =«\n \n »\n \n «m» ✓\n
\n\n Outline why the graph between P and O is negative.\n
\n\n [2]\n
\n\n The gravitational field is attractive so that energy is required «to move away from P» ✓\n
\n\n the gravitational potential is defined as 0 at\n \n , (the potential must be negative) ✓\n
\n\n the pd across the motor of the tram,\n
\n\n [2]\n
\n\n Resistance of cable = 0.072 Ω ✓\n
\n\n Pd is (500 − 0.072 × 600) = 457 V ✓\n
\n\n Calculate the difference between the magnitudes of the total energy transfers in parts (a) and (b).\n
\n\n [1]\n
\n\n Difference = 2.6175 – (1.76656 +0.84376) = 2.6175 – 2.61032 = 0.007195 «MeV»\n
\n\n \n \n OR\n \n \n
\n\n Difference = 2.6175 – (1.59587 +1.01445) = 2.61032 = 0.007195 «MeV» ✓\n
\n\n Conductor X is connected to a cell of emf\n \n E\n \n . A power of 16 W is dissipated in X.\n
\n\n Conductor Y is made from the same material with the same diameter as X but is twice as long. A cell of emf 2\n \n E\n \n is connected to Y.\n
\n\n Both cells have negligible internal resistance.\n
\n\n What power is dissipated in Y?\n
\n\n \n
\n
\n A. 8.0 W\n
\n B. 16 W\n
\n\n C. 32 W\n
\n\n D. 64 W\n
\n\n [1]\n
\n\n C\n
\n\n \n An object undergoes simple harmonic motion (shm) of amplitude\n \n \n \n \n 0\n \n . When the displacement of the object is\n \n , the speed of the object is\n \n \n \n . What is the speed when the displacement is\n \n \n \n \n 0\n \n ?\n \n
\n\n \n A. 0\n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n \n D.\n \n \n
\n\n [1]\n
\n\n A\n
\n\n The resistor has a cross-sectional area of 9.6 × 10\n \n −6\n \n m\n \n 2\n \n .\n
\n\n Show that a resistor made from carbon fibre will be suitable for the pad.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n (Calculation of length)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n l\n \n = 1.3 − 1.4 «m» ✓\n
\n \n \n ALTERNATIVE 2\n \n \n (Calculation of area)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n A\n \n = 8.3 − 9.5 × 10\n \n −6\n \n «m\n \n 2\n \n » ✓\n
\n\n \n \n ALTERNATIVE 3\n \n \n (Calculation of resistance)\n
\n Read off from graph [2.8 − 3.2 × 10\n \n −5\n \n Ω m]✓\n
\n Use of\n \n ✓\n
\n \n R\n \n = 3.6 − 4.2 «Ω» ✓\n
\n\n \n \n ALTERNATIVE 4\n \n \n (Calculation of resistivity)\n
\n Use of\n \n ✓\n
\n \n \n \n = 3.2 × 10\n \n −5\n \n «Ω m» ✓\n
\n\n Read off from graph 260 – 280 K ✓\n
\n\n Calculate the pressure of the gas in the container.\n
\n\n [1]\n
\n\n \n seen\n \n ✓\n
\n\n Show that the average rate at which thermal energy is transferred into the chocolate is about 15 W.\n
\n\n [3]\n
\n\n Reads change in temperature to be 45 − 31\n \n \n OR\n \n \n 14 °C ✓\n
\n\n
\n \n Q\n \n = 0.082 × 1.6 × 10\n \n 3\n \n × 14 = 1.84 × 10\n \n 3\n \n «J» ✓\n
\n \n P\n \n =\n \n = 15.3\n \n 15 «W»✓\n
\n\n
\n\n \n Must see either full substitution\n \n OR\n \n answer to at least 3 s.f. in\n \n MP3\n \n \n
\n\n A horizontal force\n \n acts on a sphere. A horizontal resistive force\n \n acts on the sphere where\n \n is the speed of the sphere and\n \n is a constant. What is the terminal velocity of the sphere?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n An alpha particle (\n \n ) of initial energy 5.5 MeV moves towards the centre of a nucleus of gold‑197 (\n \n ).\n
\n\n What is the distance of closest approach of the alpha particle?\n
\n\n
\n A. 1.0 × 10\n \n −13\n \n m\n
\n B. 4.1 × 10\n \n −14\n \n m\n
\n\n C. 2.1 × 10\n \n −14\n \n m\n
\n\n D. 6.6 × 10\n \n −33\n \n m\n
\n\n [1]\n
\n\n B\n
\n\n \n What is the unit of electrical potential difference expressed in fundamental SI units?\n
\n \n
\n \n A. kg m s\n \n -1\n \n C\n \n -1\n \n
\n \n
\n \n B. kg m\n \n 2\n \n s\n \n -2\n \n C\n \n -1\n \n
\n \n
\n \n C. kg m\n \n 2\n \n s\n \n -3\n \n A\n \n -1\n \n
\n \n
\n \n D. kg m\n \n 2\n \n s\n \n -1\n \n A\n \n
\n\n [1]\n
\n\n C\n
\n\n The most popular answer was B giving a low discrimination index for this question. It should be a relatively straightforward question provided the candidate can remember which of ‘C’ or ‘A’ is the fundamental unit.\n
\n\n Which quantity has the same units as those for energy stored per unit volume?\n
\n\n A. Density\n
\n\n B. Force\n
\n\n C. Momentum\n
\n\n D. Pressure\n
\n\n [1]\n
\n\n D\n
\n\n Charge flows through a liquid. The charge flow is made up of positive and negative ions. In one second 0.10 C of negative ions flow in one direction and 0.10 C of positive ions flow in the opposite direction.\n
\n\n What is the magnitude of the electric current flowing through the liquid?\n
\n\n A. 0 A\n
\n\n B. 0.05 A\n
\n\n C. 0.10 A\n
\n\n D. 0.20 A\n
\n\n [1]\n
\n\n D\n
\n\n Show that the maximum velocity of the photoelectrons is\n \n .\n
\n\n [2]\n
\n\n «\n \n » and manipulation to get\n \n \n ✓\n \n
\n\n \n \n \n OR\n \n \n \n \n ✓\n \n
\n\n \n Must see either complete substitution or calculation to at least 3 s.f. for\n \n MP2\n \n \n
\n\n An electromagnetic wave has a wavelength that is about the size of the diameter of an atom.\n
\n\n What region of the electromagnetic spectrum does the wave belong to?\n
\n\n
\n A. Infrared\n
\n B. Visible light\n
\n\n C. Ultraviolet\n
\n\n D. X-ray\n
\n\n [1]\n
\n\n D\n
\n\n Two forces act on an object in different directions. The magnitudes of the forces are 18 N and 27 N. The mass of the object is 9.0 kg. What is a possible value for the acceleration of the object?\n
\n\n A. 0 m s\n \n −2\n \n
\n\n B. 0.5 m s\n \n −2\n \n
\n\n C. 2.0 m s\n \n −2\n \n
\n\n D. 6.0 m s\n \n −2\n \n
\n\n [1]\n
\n\n C\n
\n\n Sound of frequency 2400 Hz is emitted from a stationary source towards the oscillating plate in (b). The speed of sound is 340 m s\n \n −1\n \n .\n
\n\n \n
\n Determine the maximum frequency of the sound that is received back at the source after reflection at the plate.\n
\n\n
\n\n [2]\n
\n\n frequency at plate\n \n «\n \n Hz»\n
\n\n at source\n \n «Hz» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Award\n \n [1]\n \n mark when the effect is only applied once.\n \n
\n\n \n A negatively charged particle in a uniform gravitational field is positioned mid-way between two charged conducting plates.\n \n
\n\n \n \n \n
\n \n \n The potential difference between the plates is adjusted until the particle is held at rest relative to the plates.\n \n \n
\n\n \n \n What change will cause the particle to accelerate downwards relative to the plates?\n \n \n
\n\n
\n\n \n \n A. Decreasing the charge on the particle\n
\n \n \n
\n \n \n B. Decreasing the separation of the plates\n
\n \n \n
\n \n \n C. Increasing the length of the plates\n
\n \n \n
\n \n \n D. Increasing the potential difference between the plates\n \n \n
\n\n [1]\n
\n\n A\n
\n\n State the vertical component of the total momentum of the balls after the collision.\n
\n\n [1]\n
\n\n Zero ✓\n
\n\n Show that the energy dissipated in the loop from\n \n t\n \n = 0 to\n \n t\n \n = 3.5 s is 0.13 J.\n
\n\n [2]\n
\n\n Energy is being dissipated for 0.50 s ✓\n
\n\n
\n \n «\n \n J»\n
\n \n \n OR\n \n \n
\n\n \n «\n \n J» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (b)\n \n and\n \n (c)\n \n .\n \n
\n\n \n Watch for candidates who do not justify somehow the use of 0.5 s and just divide by 2 their answer.\n \n
\n\n The electrical power rating of the hot plate is 1 kW. Comment, with reference to this value, on your answer in (a)(ii).\n
\n\n [3]\n
\n\n The answer is unrealistically large / impossible to sustain ✓\n
\n\n Due to much lower actual power, a lower temperature gradient through the base of the pot is quickly established ✓\n
\n\n The surface of the hot plate becomes colder from contact with pot\n
\n \n \n OR\n \n \n
\n there is a temperature gradient also through the hot plate ✓\n
\n Use the graph to show that the nuclear radius of silicon-30 is about 4 fm.\n
\n\n [3]\n
\n\n read off between 17 and 19 «deg» ✔\n
\n\n correct use of\n \n d\n \n =\n \n \n \n \n \n = 7.8 × 10\n \n −15\n \n «m» ✔\n
\n\n so radius =\n \n \n \n «fm» = 3.9 «fm» ✔\n
\n\n \n Award ecf for wrong angle in MP1.\n \n
\n\n \n Answer for MP3 must show at least 2\n \n \n sf.\n \n
\n\n This question was left blank by many candidates and many of those who attempted it chose an angle that when used with the correct equation gave an answer close to the given answer of 4 fm. Very few selected the correct angle, calculated the correct diameter, and divided by two to get the correct radius.\n
\n\n \n System X\n \n is at a temperature of 40 °C. Thermal energy is provided to system X until it reaches a temperature of 50 °C.\n \n System Y\n \n is at a temperature of 283 K. Thermal energy is provided to system Y until it reaches a temperature of 293 K.\n
\n\n What is the difference in the thermal energy provided to both systems?\n
\n\n A. Zero\n
\n\n B. Larger for X\n
\n\n C. Larger for Y\n
\n\n D. Cannot be determined with the data given\n
\n\n [1]\n
\n\n D\n
\n\n This question gives good discrimination although slightly more candidates chose option A instead of the correct option D. It is unusual that the correct response is 'cannot be determined' but the lack of mass or specific heat capacity in the data should have alerted candidates that they were not able to work out or compare how much thermal energy was supplied.\n
\n\n \n Calculate the ratio\n \n .\n \n
\n\n [1]\n
\n\n \n
\n\n \n 1.31 ✔\n \n
\n\n Ball 1 collides with an initially stationary ball 2 of the same mass. After the collision, the balls move with speeds\n \n and\n \n . Their velocities make angles\n \n and\n \n with the original direction of motion of ball 1.\n
\n\n \n
\n What is\n \n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n \n The coefficient of friction between the ladder and the ground is 0.400. Determine whether the ladder will slip.\n \n
\n\n [2]\n
\n\n \n maximum friction force = «\n \n 0.4 × 50N\n \n » = 20«N» ✔\n
\n \n
\n \n 14.4\n \n <\n \n 20\n \n \n AND\n \n \n so will not slip ✔\n \n
\n\n The question about the slipping of the ladder was poorly answered. The fact that the normal reaction on the floor was 50N was not known to many.\n
\n\n Calculate the emf of the cell.\n
\n\n [2]\n
\n\n 139 × 10\n \n −3\n \n (10.0 + 0.73)\n
\n\n \n \n OR\n \n \n
\n\n 29.4 × 10\n \n −3\n \n (50.0 + 0.73) ✓\n
\n\n
\n 1.49 «V» ✓\n
\n
\n\n \n Watch for\n \n ECF\n \n from 5(b)(i).\n \n
\n\n Usually well answered, regardless of b(ii), by utilising the show that value given.\n
\n\n \n Calculate\n \n F.\n \n \n
\n\n [2]\n
\n\n \n «clockwise moments = anticlockwise moments»\n
\n \n
\n \n 50 × 2cos 60 =\n \n N\n \n \n W\n \n × 4sin 60 ✔\n \n
\n\n \n \n «\n \n \n \n »\n \n \n
\n\n \n \n F\n \n =\n \n 14.4«\n \n N\n \n » ✔\n \n \n
\n\n Very few candidates could take moments about any point and correct answers were rare both at SL and HL.\n
\n\n Two objects of mass\n \n \n \n each are connected by a weightless rod of length\n \n \n \n . A force\n \n \n \n is applied to each of the objects, at right angles to the rod as shown.\n
\n\n \n
\n What is the torque acting on the system about the midpoint of the rod and what is the angular acceleration of the system?\n
\n\n
\n| \n | \n\n \n Torque\n \n | \n\n \n Angular acceleration\n \n | \n
| \n A.\n | \n\n \n | \n\n \n | \n
| \n B.\n | \n\n \n | \n\n \n | \n
| \n C.\n | \n\n \n | \n\n \n | \n
| \n D.\n | \n\n \n | \n\n \n | \n
\n [1]\n
\n\n A\n
\n\n State the initial acceleration of the raindrop.\n
\n\n [1]\n
\n\n \n g\n \n \n \n OR\n \n \n 9.81 «m s\n \n −2\n \n »\n \n \n OR\n \n \n acceleration of gravity/due to free fall ✓\n
\n\n
\n\n \n Accept 10 «\n \n m s\n \n −2\n \n \n ».\n \n
\n\n \n Ignore sign.\n \n
\n\n \n Do\n \n not\n \n accept bald “gravity”.\n \n
\n\n \n Accept answer that indicates tangent of the graph at time t=0.\n \n
\n\n A nice introductory question answered correctly by most candidates. Most answers quoted the data booklet value, with a few 10's or 9.8's, or the answer in words. Very few lost the mark by just stating gravity, or zero.\n
\n\n A person with a weight of\n \n stands on a scale in an elevator.\n
\n\n \n
\n What is the acceleration of the elevator when the scale reads\n \n ?\n
\n\n A.\n \n downwards\n
\n\n B.\n \n downwards\n
\n\n C.\n \n upwards\n
\n\n D.\n \n upwards\n
\n\n [1]\n
\n\n D\n
\n\n Show that the net torque on the system about the central axis is approximately 30 N m.\n
\n\n [1]\n
\n\n \n = 50 × 0.5 + 40 × 0.2\n
\n\n \n \n OR\n \n \n
\n\n 33 «Nm» ✓\n
\n\n
\n\n \n Accept opposite rotational sign convention\n \n
\n\n A particle is moving in a straight line with an acceleration proportional to its displacement and opposite to its direction. What are the velocity and the acceleration of the particle when it is at its maximum displacement?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n A throw is made once every minute. Estimate the average time required before a throw occurs where all coins are heads or all coins are tails.\n
\n\n [2]\n
\n\n Two chances in 1024 so once every 512 throws ✓\n
\n\n 512 throws take 8.5 h so (a reasonable estimate is half way through) on average 4.3 h ✓\n
\n\n Which graph shows the variation of activity\n \n with time\n \n for a radioactive nuclide?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n Calculate the mass of the oil that remains unfrozen after\n \n minutes.\n
\n\n [2]\n
\n\n \n mass of frozen oil\n \n \n \n ✓\n \n
\n\n \n unfrozen mass\n \n \n \n ✓\n \n
\n\n Show that the time taken for the ball to reach the surface of the table is about 0.2 s.\n
\n\n [1]\n
\n\n \n t\n \n = «\n \n =» 0.22 «s»\n
\n \n \n OR\n \n \n
\n \n t\n \n =\n \n \n ✓\n \n
\n\n \n Answer to 2 or more significant figures or formula with variables replaced by correct values.\n \n
\n\n Determine the average magnitude of\n \n \n \n .\n
\n\n [2]\n
\n\n Average torque\n \n «N m» ✓\n
\n\n Average force\n \n «N» ✓\n
\n\n State what is meant by an elastic collision.\n
\n\n [1]\n
\n\n No change in the kinetic energy of the system ✓\n
\n\n Radioactive nuclide X decays into a stable nuclide Y. The decay constant of X is λ. The variation with time\n \n t\n \n of number of nuclei of X and Y are shown on the same axes.\n
\n\n \n
\n What is the expression for\n \n s\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Determine the fractional number of throws for which the three most likely macrostates occur.\n
\n\n
\n\n [3]\n
\n\n Recognises that 4 heads and 6 tails also required ✓\n
\n\n Total number of microstates = 672 ✓\n
\n\n Fractional number = 672/1024 = 0.66 ✓\n
\n\n
\n\n \n Allow ecf for MP3\n \n
\n\n Photons with energy 1.1 × 10\n \n −18\n \n J are incident on a third metal surface. The maximum energy of electrons emitted from the surface of the metal is 5.1 × 10\n \n −19\n \n J.\n
\n\n Calculate, in eV, the work function of the metal.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n work function\n \n \n ✓\n \n
\n\n \n
\n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n Some energy levels for a hydrogen atom are shown.\n
\n\n \n diagram not to scale\n \n
\n\n \n
\n What is the\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D. 2\n
\n\n [1]\n
\n\n C\n
\n\n Explain why the intensity of light at\n \n = 0 is 4\n \n .\n
\n\n [2]\n
\n\n The amplitude «at\n \n x\n \n = 0» will be doubled ✓\n
\n\n intensity is proportional to amplitude squared /\n \n ∝\n \n A\n \n \n 2\n \n ✓\n
\n\n State the value of the resultant force on the aircraft when hovering.\n
\n\n [1]\n
\n\n \n zero\n \n \n ✓\n \n
\n\n A student measures the length\n \n l\n \n and width\n \n w\n \n of a rectangular table top.\n
\n\n What is the absolute uncertainty of the perimeter of the table top?\n
\n\n \n
\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The astronomical unit (\n \n ) and light year (\n \n ) are convenient measures of distance in astrophysics. Define each unit.\n
\n\n \n :\n
\n\n \n :\n
\n\n [2]\n
\n\n \n \n \n :\n \n \n \n «\n \n \n average\n \n \n »\n \n \n distance from the Earth to the Sun\n \n \n ✓\n
\n \n
\n \n \n \n :\n \n distance light travels in one year\n \n \n ✓\n \n
\n\n The diagram shows field lines for an electrostatic field. X and Y are two points on the same field line.\n
\n\n \n
\n Outline which of the two points has the larger electric potential.\n
\n\n [2]\n
\n\n potential greater at Y ✓\n
\n\n
\n\n «from\n \n » the potential increases in the direction opposite to field strength «so from X to Y»\n
\n\n \n \n OR\n \n \n
\n\n opposite to the direction of the field lines, «so from X to Y»\n
\n\n \n \n OR\n \n \n
\n\n «from\n \n » work done to move a positive charge from X to Y is positive «so the potential increases from X to Y» ✓\n
\n\n A significant majority guessed at X, probably because the field lines are closer together. Those that identified Y were generally successful in their explanation.\n
\n\n Show that the phase difference between the oscillations of the two corks is\n \n radians.\n
\n\n [1]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n Phase difference is\n \n ×\n \n ✓\n
\n «=\n \n » ✓\n
\n \n ALTERNATIVE 2\n \n
\n\n One wavelength/period represents «phase difference» of 2\n \n and «corks» are ½ wavelength/period apart so phase difference is\n \n /\n \n \n OWTTE\n \n \n ✓\n
\n\n A metallic surface is first irradiated with infrared radiation and photoelectrons are emitted from the surface. The infrared radiation is replaced by ultraviolet radiation of the same intensity.\n
\n\n What will be the change in the kinetic energy of the photoelectrons and the rate at which they are ejected?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n With a low difficulty index, fewer than 15 % of candidates correctly selected response A. The large majority of candidates selected response C. These candidates likely did not recognize that since intensity stays constant, there must be fewer ultraviolet photons ejected for the power per unit area to remain constant. The discrimination index was very low for this question.\n
\n\n Two ideal gases X and Y are at the same temperature. The mass of a particle of gas X is larger than the mass of a particle of gas Y. Which is correct about the average kinetic energy and the average speed of the particles in gases X and Y?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Outline why it is unlikely that the relationship between\n \n T\n \n and\n \n V\n \n is linear.\n
\n\n [1]\n
\n\n it is not possible to draw a straight line through all the error bars ✓\n
\n\n Outline why work must be done on ring B as it moves towards ring A at a constant speed.\n
\n\n [2]\n
\n\n the current induced in B gives rise to a magnetic field opposing that of A\n
\n\n \n OR\n \n
\n\n there will be a magnetic force opposing the motion ✓\n
\n\n work must be done to move B in the opposite direction to this force ✓\n
\n\n The conservation of which quantity explains Lenz’s law?\n
\n\n A. Charge\n
\n\n B. Energy\n
\n\n C. Magnetic field\n
\n\n D. Mass\n
\n\n [1]\n
\n\n B\n
\n\n A variable resistor is connected to a cell with emf\n \n ε\n \n and internal resistance\n \n r\n \n as shown. When the current in the circuit is\n \n I\n \n , the potential difference measured across the terminals of the cell is\n \n V\n \n .\n
\n\n \n
\n The resistance of the variable resistor is doubled.\n
\n\n What is true about the current and the potential difference?\n
\n\n
\n| \n | \n\n \n Current\n \n | \n\n \n Potential difference\n \n | \n
| \n A.\n | \n\n greater than\n \n | \n\n greater than\n \n V\n \n | \n
| \n B.\n | \n\n less than\n \n | \n\n greater than\n \n V\n \n | \n
| \n C.\n | \n\n greater than\n \n | \n\n equal to\n \n V\n \n | \n
| \n D.\n | \n\n less than\n \n | \n\n equal to\n \n V\n \n | \n
\n
\n\n [1]\n
\n\n A\n
\n\n The standing wave on the string creates a travelling sound wave in the surrounding air.\n
\n\n Outline\n \n two\n \n differences between a standing wave and a travelling wave.\n
\n\n [2]\n
\n\n travelling waves transfer energy\n \n \n OR\n \n \n standing waves don’t ✓\n
\n\n amplitude of oscillation varies along a standing wave\n \n \n OR\n \n \n is constant along a travelling wave ✓\n
\n\n standing waves have nodes and antinodes\n \n \n OR\n \n \n travelling waves don’t ✓\n
\n\n points in an internodal region have same phase in standing waves\n \n \n OR\n \n \n different phase in travelling waves ✓\n
\n\n This question was answered well. Students showed to be familiar with the differences between standing and travelling waves. In SL they had to identify two differences, so that proved to be more challenging.\n
\n\n Samples of two radioactive nuclides X and Y are held in a container. The number of particles of X is half the number of particles of Y. The half-life of X is twice the half-life of Y.\n
\n\n What is the initial value of\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n \n As the spaceship passes the Earth it emits a flash of light that travels in the same direction as the spaceship with speed\n \n c\n \n as measured by an observer on the spaceship. Calculate, according to the Galilean transformation, the speed of the light in the Earth’s reference frame.\n \n
\n\n [1]\n
\n\n \n 1.5\n \n \n \n c\n \n \n \n ✔\n \n
\n\n Almost no incorrect answers were seen.\n
\n\n Outline, using (b)(i), why it is not correct to use the equation\n \n to calculate the speed required for the spacecraft to reach infinity from the surface of\n \n .\n
\n\n [1]\n
\n\n «this is the escape speed for\n \n alone but» gravitational potential / field of Jupiter must be taken into account\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n Draw an arrow on the diagram to represent the direction of the acceleration of the satellite.\n
\n\n [1]\n
\n\n arrow normal to the orbit towards the Earth ✓\n
\n\n Determine the velocity of the first curling stone.\n
\n\n [2]\n
\n\n 2.04 m s\n \n −1\n \n ✓\n
\n\n At 7.9° to initial direction ✓\n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n A rectangular conducting coil rotates at a constant angular velocity in a uniform magnetic field. The rotation axis of the coil is perpendicular to the field.\n
\n\n \n
\n At one instant the plane of the coil is at an angle\n \n θ\n \n to the direction of the field.\n
\n\n The magnitude of the emf induced in the coil is\n
\n\n
\n A. never zero.\n
\n B. at a maximum when\n \n θ\n \n = 0° or 180°.\n
\n\n C. at a maximum when\n \n θ\n \n = 45° or 225°.\n
\n\n D. at a maximum when\n \n θ\n \n = 90° or 270°.\n
\n\n [1]\n
\n\n B\n
\n\n \n Show that the radius of the path is about 6 cm.\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n \n \n \n \n OR\n \n \n 0.060 « m »\n \n
\n\n \n \n NOTE: Award MP2 for full replacement or correct answer to at least 2 significant figures\n \n \n
\n\n The graph shows the variation of torque with time acting on a rotating object.\n
\n\n \n
\n What is the angular impulse acting on the object?\n
\n\n
\n A. The gradient of the line PQ\n
\n B. The average gradient of the line PQR\n
\n\n C. The area under the line PQ\n
\n\n D. The area under the line PQR\n
\n\n [1]\n
\n\n D\n
\n\n The following data for the Mars–Phobos system and the Earth–Moon system are available:\n
\n\n Mass of Earth = 5.97 × 10\n \n 24\n \n kg\n
\n\n The Earth–Moon distance is 41 times the Mars–Phobos distance.\n
\n\n The orbital period of the Moon is 86 times the orbital period of Phobos.\n
\n\n Calculate, in kg, the mass of Mars.\n
\n\n [2]\n
\n\n \n \n \n \n \n or other consistent re-arrangement ✔\n
\n\n 6.4 × 10\n \n 23\n \n «kg» ✔\n
\n\n
\n\n This question was challenging for candidates. The candidates who started down the correct path of using the given derived value from 5bi often simply forgot that the multiplication factors had to be squared and cubed as well as the variables.\n
\n\n There is an advantage and a disadvantage in using two masses that are almost equal.\n
\n\n State and explain the disadvantage with reference to your answer to (a)(ii).\n
\n\n [2]\n
\n\n the percentage error in the difference of the masses is large ✔\n
\n\n leading to a large percentage error/uncertainty in g/of the experiment ✔\n
\n\n \n Do not accept ideas related to the mass/moment of inertia of the pulley.\n \n
\n\n In part ii) many were able to appreciate that the resultant percentage error in “g” was relatively large however linking this with what caused the large uncertainty (that is, the high % error from the small difference in masses) proved more challenging.\n
\n\n State the units of\n \n A\n \n .\n
\n\n [1]\n
\n\n kV s ✓\n
\n\n Compare and contrast spontaneous and neutron-induced nuclear fission.\n
\n\n [2]\n
\n\n Spontaneous fission occurs with no external influence, neutron-induced fission requires an interaction with a neutron «of appropriate energy» ✓\n
\n\n Both result in the release of energy\n
\n \n \n OR\n \n \n
\n both have a large number of possible pairs of products ✓\n
\n Monochromatic light of wavelength\n \n \n \n is incident on two slits S\n \n 1\n \n and S\n \n 2\n \n . An interference pattern is observed on the screen.\n
\n\n \n
\n O is equidistant from S\n \n 1\n \n and S\n \n 2\n \n . A bright fringe is observed at O and a dark fringe at X.\n
\n\n There are two dark fringes between O and X. What is the path difference between the light arriving at X from the two slits?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n With a relatively high discrimination index, this question was well answered by stronger HL candidates. Some students had difficulty recognising that there would be 2.5λ rather than 1.5λ, and as a result option B was a significant distractor.\n
\n\n The road from city X to city Y is 1000 km long. The displacement is 800 km from X to Y.\n
\n\n \n
\n What is the distance travelled from Y to X and the displacement from Y to X?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n P and Q are two opposite point charges. The force\n \n F\n \n acting on P due to Q and the electric field strength\n \n E\n \n at P are shown.\n
\n\n \n
\n Which diagram shows the force on Q due to P and the electric field strength at Q?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Option A was the most frequent answer selected by both HL and SL candidates, suggesting that determining the direction of the electric field was more problematic than the direction of the force (Newton 3).\n
\n\n The graph shows the variation of electric field strength\n \n with distance\n \n from a point charge.\n
\n\n \n
\n The shaded area X is the area under the graph between two separations\n \n and\n \n from the charge.\n
\n\n What is X?\n
\n\n A. The electric field average between\n \n and\n \n
\n\n B. The electric potential difference between\n \n and\n \n
\n\n C. The work done in moving a charge from\n \n to\n \n
\n\n D. The work done in moving a charge from\n \n to\n \n
\n\n [1]\n
\n\n B\n
\n\n The temperature of the air outside of the bottle is 20 °C. The surface area of the bottle is 4.0 × 10\n \n −2\n \n m\n \n 2\n \n . Calculate the initial rate of thermal energy transfer by conduction through the bottle.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n 480 «W» ✓\n
\n\n A battery of negligible internal resistance is connected to a lamp. A second identical lamp is added in series. What is the change in potential difference across the first lamp and what is the change in the output power of the battery?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Identify the direction of the magnetic force on the wire.\n
\n\n [1]\n
\n\n into the plane «of the paper» ✓\n
\n\n Generally, a well answered question although there was some confusion on how to communicate it, with some contradictory answers indicating into or out, and also North or South at the same time.\n
\n\n A variable force with a maximum\n \n F\n \n \n max\n \n is applied to an object over a time interval\n \n T\n \n . The object has a mass\n \n m\n \n and is initially at rest.\n
\n\n \n
\n What is the speed of the object at time\n \n T\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n F\n \n \n max\n \n \n Tm\n \n
\n\n D. 2\n \n F\n \n \n max\n \n \n Tm\n \n
\n\n [1]\n
\n\n A\n
\n\n Calculate the efficiency of the cycle.\n
\n\n [1]\n
\n\n e « = 1 −\n \n \n \n \n \n = 1 −\n \n \n \n » = 0.45 ✔\n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n A charge\n \n Q\n \n is at a point between two electric charges\n \n Q\n \n \n 1\n \n and\n \n Q\n \n \n 2\n \n . The net electric force on Q is zero. Charge\n \n Q\n \n \n 1\n \n is further from\n \n Q\n \n than charge\n \n Q\n \n \n 2\n \n .\n
\n\n What is true about the signs of the charges\n \n Q\n \n \n 1\n \n and\n \n Q\n \n \n 2\n \n and their magnitudes?\n
\n\n \n
\n \n
\n [1]\n
\n\n A\n
\n\n Calculate the efficiency of the cycle.\n
\n\n [1]\n
\n\n e « = 1 −\n \n \n \n \n \n = 1 −\n \n \n \n » = 0.45 ✔\n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n For the propellor,\n \n and\n \n .\n
\n\n Calculate the moment of inertia of the propellor.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Outline why the cylinder performs simple harmonic motion when released.\n
\n\n [1]\n
\n\n \n the\n \n \n «\n \n \n restoring\n \n \n »\n \n \n force/acceleration is proportional to displacement\n \n \n ✓\n \n
\n\n \n \n
\n Allow use of symbols i.e.\n \n \n \n or\n \n \n \n
\n This was well answered with candidates gaining credit for answers in words or symbols.\n
\n\n \n The escape speed from a planet of radius\n \n R\n \n is\n \n v\n \n \n esc\n \n . A satellite orbits the planet at a distance\n \n R\n \n from the surface of the planet. What is the orbital speed of the satellite?\n \n
\n\n \n A.\n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n
\n\n [1]\n
\n\n A\n
\n\n This had a very low discrimination index with the majority of candidates choosing B, followed by C. Response A, the correct answer, was third in popularity. The candidates missed that the satellite orbits at a distance of R from the surface of a planet of radius R so the total distance to be considered was 2R.\n
\n\n A net force\n \n acts on an object of mass\n \n that is initially at rest. The object moves in a straight line. The variation of\n \n with the distance\n \n is shown.\n
\n\n \n
\n What is the speed of the object at the distance\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Outline, with reference to the decay equation above, the role of chain reactions in the operation of a nuclear power station.\n
\n\n [3]\n
\n\n The four neutrons released in the reaction may initiate further fissions ✓\n
\n\n «If sufficient U-235 is available,» the reaction is self-sustained ✓\n
\n\n Allowing for the continuous production of energy ✓\n
\n\n The number of neutrons available is controlled with control rods «to maintain the desired reaction rate» ✓\n
\n\n Outline why electrons with energy of approximately\n \n would be unsuitable for the investigation of nuclear radii.\n
\n\n [2]\n
\n\n \n the de Broglie wavelength of electrons is\n \n \n «\n \n \n much\n \n \n »\n \n \n longer than the size of a nucleus\n \n \n ✓\n \n
\n\n \n
\n \n \n hence electrons would not undergo diffraction\n
\n \n \n \n \n OR\n \n \n
\n \n \n no diffraction pattern would be observed\n \n \n ✓\n \n
\n Candidates generally scored poorly on this question. There was confusion between this experiment and another diffraction one, so often the new wavelength was compared to the spacing between atoms. Also, in line with answers to b(i) there were suggestions that the electrons did not have sufficient energy to reach the nucleus or would be deflected by too great an angle to be seen.\n
\n\n The density of an ideal gas is 1.4 kg m\n \n −3\n \n when its pressure is 0.1 MPa.\n
\n\n What is the average translational speed of the gas molecules?\n
\n\n
\n A. 0.46 m s\n \n −1\n \n
\n B. 270 m s\n \n −1\n \n
\n\n C. 460 m s\n \n −1\n \n
\n\n D. 71 km s\n \n −1\n \n
\n\n [1]\n
\n\n C\n
\n\n In the decay of polonium-210, alpha emission can be followed by the emission of a gamma photon.\n
\n\n State and explain whether the alpha particle or gamma photon will cause greater ionization in the surrounding material.\n
\n\n [2]\n
\n\n alpha particle ✓\n
\n\n is electrically charged hence more likely to interact with electrons «in the surrounding material» ✓\n
\n\n Many did not interpret the stem correctly and failed to compare the ionisation of alpha particles versus gamma rays.\n
\n\n Outline how a standing wave is produced on the string.\n
\n\n [2]\n
\n\n «travelling» wave moves along the length of the string and reflects «at fixed end»\n \n ✓\n \n
\n\n superposition/interference of incident and reflected waves\n \n ✓\n \n
\n\n the superposition of the reflections is reinforced only for certain wavelengths\n \n ✓\n \n
\n\n Draw and label on diagram B the forces acting on the sphere just after it has been released.\n
\n\n [1]\n
\n\n \n
\n buoyancy force greater than weight ✓\n
\n\n \n \n Award [1]\n \n for correct labeling\n \n AND\n \n relative size.\n \n
\n\n \n Allow any point, where the forces are drawn.\n \n
\n\n The orbital period\n \n T\n \n of a moon orbiting a planet of mass\n \n M\n \n is given by\n
\n\n \n \n \n \n \n
\n\n where\n \n R\n \n is the average distance between the centre of the planet and the centre of the moon.\n
\n\n Show that\n \n \n \n \n \n
\n\n [3]\n
\n\n \n \n ALTERNATE 1\n \n \n
\n\n «using fundamental equations»\n
\n\n use of Universal gravitational force/acceleration/orbital velocity equations ✔\n
\n\n equating to centripetal force or acceleration. ✔\n
\n\n rearranges to get\n \n \n \n \n \n ✔\n
\n\n \n \n ALTERNATE 2\n \n \n
\n\n «starting with\n \n \n \n \n \n »\n \n \n
\n\n substitution of proper equation for T from orbital motion equations ✔\n
\n\n substitution of proper equation for M\n \n \n OR\n \n \n R from orbital motion equations ✔\n
\n\n rearranges to get\n \n \n \n \n \n ✔\n
\n\n This was another “show that” derivation. Many candidates attempted to work with universal gravitation equations, either from memory or the data booklet, to perform this derivation. The variety of correct solution paths was quite impressive, and many candidates who attempted this question were able to receive some marks. Candidates should be reminded on “show that” questions that it is never allowed to work backwards from the given answer. Some candidates also made up equations (such as T = 2𝝿r) to force the derivation to work out.\n
\n\n \n The expected value of\n \n \n \n \n \n is\n \n . Comment on your result\n \n .\n
\n\n [1]\n
\n\n \n Experimental value matches this/correct, as expected value within the range\n \n \n ✓\n
\n \n \n \n \n OR\n \n \n
\n \n \n experimental value does not match/incorrect, as it is not within range\n \n \n ✓\n \n
\n Outline why component X is considered non-ohmic.\n
\n\n [1]\n
\n\n \n current is not «directly» proportional to the potential difference\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X is not constant\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X changes «with current/voltage»\n \n \n ✓\n \n
\n Most answers that didn't score simply referred to the shape of the graph without any explanation as to what this meant to the relationship between the variables.\n
\n\n A conductor is placed in a uniform magnetic field perpendicular to the plane of the paper. A force\n \n F\n \n acts on the conductor when there is a current in the conductor as shown.\n
\n\n \n
\n The conductor is rotated 30° about the axis of the magnetic field.\n
\n\n \n
\n What is the direction of the magnetic field and what is the magnitude of the force on the conductor after the rotation?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n This question requires careful reading by the candidate. Candidates needed to appreciate that the rotation relative to the magnetic field axis still produces a 90 degree angle between the conductor and the field. Option D was a very effective distractor for students.\n
\n\n A mass\n \n of a liquid of specific heat capacity\n \n flows every second through a heater of power\n \n . What is the difference in temperature between the liquid entering and leaving the heater?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Explain the direction in which the person-turntable system starts to rotate.\n
\n\n [3]\n
\n\n \n «person rotates» anticlockwise\n \n \n ✓\n \n
\n\n \n the person gains angular momentum «in the opposite direction to the new wheel motion\n \n \n »\n \n \n ✓\n \n
\n\n \n so that the total angular momentum is conserved\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n \n \n Award\n \n \n \n [1 max]\n \n \n \n for a bald statement of conservation of angular momentum\n \n \n
\n\n Show that the internal resistance of the cell is about 0.7 Ω.\n
\n\n [2]\n
\n\n current\n \n «A» ✓\n
\n\n \n r\n \n \n \n \n OR\n \n \n \n «Ω» ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , allow any other correctly substituted expression for r.\n \n
\n\n Many answers here produced a number that did not round to 0.7 but students claimed it did. The simultaneous equation approach was seen in the best candidates, getting the right answer. It is worthy of reminding about the need of showing one more decimal place when calculating a show that value type of question.\n
\n\n \n The graph also shows the displacement of two particles, P and Q, in the medium at\n \n t\n \n = 0. State and explain which particle has the larger magnitude of acceleration at\n \n t\n \n = 0.\n \n
\n\n [2]\n
\n\n \n Q ✔\n
\n acceleration is proportional to displacement «and Q has larger displacement» ✔\n \n
\n Show that the gravitational potential\n \n V\n \n \n P\n \n at the surface of P due to the mass of P is given by\n \n V\n \n \n P\n \n = −\n \n g\n \n \n P\n \n \n R\n \n \n P\n \n where\n \n R\n \n \n P\n \n is the radius of the planet.\n
\n\n [2]\n
\n\n \n V\n \n \n P\n \n =\n \n \n \n AND\n \n g\n \n \n P\n \n =\n \n (at surface) ✓\n
\n\n Suitable working and cancellation of\n \n G\n \n and\n \n M\n \n seen ✓\n
\n\n \n V\n \n \n P\n \n = −\n \n g\n \n \n P\n \n \n R\n \n \n P\n \n
\n\n \n Must see negative sign\n \n
\n\n
\n\n Calculate, in m s\n \n −1\n \n , the maximum velocity of vibration of point P when it is vibrating with a frequency of 195 Hz.\n
\n\n [2]\n
\n\n max velocity occurs at x = 0\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n Outline, by reference to nuclear binding energy, why the mass of a nucleus is less than the sum of the masses of its constituent nucleons.\n
\n\n [2]\n
\n\n according to Δ\n \n E\n \n = Δ\n \n mc\n \n \n 2\n \n / identifies mass energy equivalence ✓\n
\n\n
\n\n energy is released when nucleons come together / a nucleus is formed «so nucleus has less mass than individual nucleons»\n
\n\n \n \n OR\n \n \n
\n\n energy is required to «completely» separate the nucleons / break apart a nucleus «so individual nucleons have more mass than nucleus» ✓\n
\n\n
\n\n \n Accept protons and neutrons.\n \n
\n\n Still several answers that thought that the nucleus needed to gain energy to bind it together. Most candidates scored at least one for recognising some form of mass/energy equivalence, although few candidates managed to consistently express their ideas here.\n
\n\n Calculate the value of the centripetal force.\n
\n\n [1]\n
\n\n \n «N»\n \n ✓\n \n
\n\n Determine the resistance of the variable resistor.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n voltage across X\n \n ✓\n \n
\n\n \n voltage across R\n \n ✓\n \n
\n\n \n resistance of variable resistor\n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n overall resistance\n \n ✓\n
\n\n resistance of X\n \n ✓\n
\n\n resistance of variable resistor\n \n ✓\n
\n\n Two identical blocks, each of mass\n \n m\n \n and speed\n \n v\n \n , travel towards each other on a frictionless surface.\n
\n\n \n
\n The blocks undergo a head-on collision. What is definitely true\n \n immediately\n \n after the collision?\n
\n\n A. The momentum of each block is zero.\n
\n\n B. The total momentum is zero.\n
\n\n C. The momentum of each block is 2\n \n mv\n \n .\n
\n\n D. The total momentum is 2\n \n mv\n \n .\n
\n\n [1]\n
\n\n B\n
\n\n A child stands on a horizontal rotating platform that is moving at constant angular speed. The centripetal force on the child is provided by\n
\n\n A. the gravitational force on the child.\n
\n\n B. the friction on the child’s feet.\n
\n\n C. the tension in the child’s muscles.\n
\n\n D. the normal reaction of the platform on the child.\n
\n\n [1]\n
\n\n B\n
\n\n What is the unit of power expressed in fundamental SI units?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The quantity\n \n is known as the Compton wavelength.\n
\n\n Show that the Compton wavelength is about 2.4 pm.\n
\n\n [1]\n
\n\n 2.43 pm ✓\n
\n\n A train is moving in a straight line away from a stationary observer when the train horn emits a sound of frequency\n \n . The speed of the train is\n \n where\n \n is the speed of sound. What is the frequency of the horn as heard by the observer?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n What is true for the Bohr model for the hydrogen atom?\n
\n\n A. Angular momentum of electrons is quantized.\n
\n\n B. Electrons are described by wave functions.\n
\n\n C. Electrons never exist in fixed orbitals.\n
\n\n D. Electrons will continuously emit radiation.\n
\n\n [1]\n
\n\n A\n
\n\n The mass of the wire is 18 g. The specific heat capacity of copper is 385 J kg\n \n −1\n \n K\n \n −1\n \n . Estimate the increase in temperature of the wire.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «K» ✓\n
\n\n
\n\n \n Allow\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Award\n \n [1]\n \n for a\n \n POT\n \n error in\n \n MP1\n \n .\n \n
\n\n Calculate, using your answer to (b)(i), the time taken by the propellor to attain this rotational speed.\n
\n\n [2]\n
\n\n \n used ✓\n
\n\n 0.25 s ✓\n
\n\n The graph shows the variation with time of the resultant net force acting on an object. The object has a mass of 1kg and is initially at rest.\n
\n\n \n
\n What is the velocity of the object at a time of 200 ms?\n
\n\n A. 8 m s\n \n –1\n \n
\n\n B. 16 m s\n \n –1\n \n
\n\n C. 8 km s\n \n –1\n \n
\n\n D. 16 km s\n \n –1\n \n
\n\n [1]\n
\n\n A\n
\n\n Many candidates (incorrectly) selected response B, perhaps neglecting the changing value of force over time.\n
\n\n Some of the nuclear energy levels of oxygen-14 (\n \n 14\n \n O) and nitrogen-14 (\n \n 14\n \n N) are shown.\n
\n\n \n
\n A nucleus of\n \n 14\n \n O decays into a nucleus of\n \n 14\n \n N with the emission of a positron and a gamma ray. What is the maximum energy of the positron and the energy of the gamma ray?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n An electron has a linear momentum of 4.0 × 10\n \n −25\n \n kg m s\n \n −1\n \n . What is the order of magnitude of the kinetic energy of the electron?\n
\n\n A. 10\n \n −50\n \n J\n
\n\n B. 10\n \n −34\n \n J\n
\n\n C. 10\n \n −19\n \n J\n
\n\n D. 10\n \n 6\n \n J\n
\n\n [1]\n
\n\n C\n
\n\n A liquid is vaporized to a gas at a constant temperature.\n
\n\n Three quantities of the substance are the\n
\n\n I. total intermolecular potential energy\n
\n II. root mean square speed of the molecules\n
\n III. average distance between the molecules.\n
\n Which quantities are\n \n greater\n \n for the substance in the gas phase compared to the liquid phase?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n Determine the largest magnitude of\n \n F\n \n for which the block and the object do not move relative to each other.\n
\n\n [3]\n
\n\n \n F\n \n = 60\n \n a ✓\n \n
\n\n \n F\n \n \n f\n \n = 0.6 × 15 × 9.8 «= 88.2 N» ✓\n
\n\n \n «N» ✓\n
\n\n
\n\n \n Allow use of a =\n \n 0.6\n \n g leading to 353 N.\n \n
\n\n \n The mass of a helium atom is 6.6 × 10\n \n -27\n \n kg. Estimate the average speed of the helium atoms in the container.\n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n v =\n \n \n \n 1.4 × 10\n \n 3\n \n \n «ms\n \n –1\n \n »\n \n \n \n ✔\n \n \n \n
\n\n \n \n
\n\n At HL this was very well answered but at SL many just worked out E=3/2kT and left it as a value for KE.\n
\n\n \n A proton, an electron and an alpha particle are at rest. Which particle has the smallest magnitude of ratio of charge to mass and which particle has the largest magnitude of ratio of charge to mass?\n \n
\n\n \n
\n [1]\n
\n\n A\n
\n\n In an experiment, alpha particles of initial kinetic energy 5.9 MeV are directed at stationary nuclei of lead (\n \n ). Show that the distance of closest approach is about 4 × 10\n \n −14\n \n m.\n
\n\n [2]\n
\n\n 2e\n \n \n AND\n \n \n 82e seen\n
\n\n \n \n OR\n \n \n
\n\n 3.2 × 10\n \n −19\n \n «C»\n \n \n AND\n \n \n 1.312 × 10\n \n −17\n \n «C» seen ✓\n
\n\n \n d\n \n =\n \n = 3.998 × 10\n \n −14\n \n ≈ 4 × 10\n \n −14\n \n «m» ✓\n
\n\n \n Must see either clear substitutions or answer to at least 4 s.f. for\n \n MP2\n \n .\n \n
\n\n Just before the collision of the ball with the block,\n
\n\n
\n\n Tension upwards, weight downwards ✓\n
\n Tension is clearly longer than weight ✓\n
\n
\n\n \n Look for:\n \n
\n\n \n
\n \n Show that the tennis ball passes over the net.\n \n
\n\n [3]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n \n
\n\n \n \n u\n \n y\n \n \n \n =64sin7/7.80«ms\n \n –1\n \n »\n \n ✔\n \n
\n\n \n decrease in height = 7.80 × 0.187 +\n \n \n \n × 9.81 × 0.187\n \n 2\n \n \n / 1.63«m»\n \n ✔\n \n
\n\n final height =\n \n «2.80 – 1.63\n \n \n »\n \n = 1.1/1.2\n \n «m\n \n \n » ✔\n \n \n
\n \n
\n \n «higher than net so goes over»\n \n
\n\n \n
\n \n \n ALTERNATIVE 2\n \n \n \n
\n vertical distance to fall to net\n \n «=2.80 – 0.91\n \n \n » = 1.89«m» ✔\n \n
\n\n \n time to fall this distance found using «\n \n \n \n \n \n »\n \n
\n\n \n \n \n \n \n \n \n = 0.21\n \n «s\n \n \n » ✔\n \n \n \n
\n\n \n \n \n 0.21«s» > 0.187«s» ✔\n \n \n \n \n
\n \n
\n \n «reaches the net before it has fallen far enough so goes over»\n \n
\n\n There were a number of approaches students could take to answer this and examiners saw examples of them all. One approach taken was to calculate the time taken to fall the distance to the top of the net and to compare this with the time calculated in bi) for the ball to reach the net. This approach, which is shown in the mark scheme, required solving a quadratic in t which is beyond the mathematical requirements of the syllabus. This mathematical technique was only required if using this approach and not required if, for example, calculating heights.\n
\n\n A common mistake was to forget that the ball has a vertical acceleration. Examiners were able to award credit/ECF for correct parts of an otherwise flawed method.\n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n The electromagnetic spectrum radiated by a black body at temperature\n \n T\n \n shows a peak at wavelength\n \n \n p\n \n .\n
\n\n What is the variation of\n \n \n p\n \n with\n \n T\n \n ?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n A large proportion of the candidates, especially at SL, picked the incorrect alternative D, probably triggered by the shape of the graph being similar to the spectral distribution of black-body radiation. The question required an application of Wien's law and the inverse proportionality of the peak wavelength with temperature.\n
\n\n A particle undergoes simple harmonic motion of period\n \n . At time\n \n the particle is at its equilibrium position.\n
\n\n What is\n \n when the particle is at its greatest distance from the equilibrium position?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Determine the efficiency of the cycle.\n
\n\n [2]\n
\n\n Net work done = «\n \n » 9.77 «kJ» ✓\n
\n\n Efficiency =«\n \n » 0.47 ✓\n
\n\n \n The lines of the minimum and maximum gradient are shown.\n \n
\n\n \n \n \n
\n \n \n Estimate the absolute uncertainty in\n \n a\n \n .\n \n \n
\n\n [2]\n
\n\n \n «s» ±0.001 «s»\n \n \n AND\n \n \n \n «s» ±0.001 «s» ✔\n
\n\n «\n \n » 0.003 «s» ✔\n
\n\n \n The diagram shows some of the electric field lines for two fixed, charged particles X and Y.\n \n
\n\n \n \n \n
\n \n \n The magnitude of the charge on X is\n \n \n \n and that on Y is\n \n \n \n \n \n . The distance between X and Y is 0.600 m. The distance between P and Y is 0.820 m.\n \n \n
\n\n \n \n At P the electric field is zero. Determine, to\n \n one\n \n significant figure, the ratio\n \n \n \n .\n \n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n \n \n \n \n ✔\n \n \n \n
\n\n
\n\n The majority of candidates had an idea of the basic technique here but it was surprisingly common to see the squared missing from the expression for field strengths.\n
\n\n Show that, when sound travels from clay to sandstone, the critical angle is approximately 40°.\n
\n\n [2]\n
\n\n \n \n c\n \n n\n \n s\n \n \n \n ✓\n
\n\n Critical angle\n \n ✓\n
\n\n In one particular event, a maximum emf of 65 mV is generated in the geophone. The geophone coil has 150 turns.\n
\n\n Calculate the rate of flux change that leads to this emf.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n \n
\n\n \n mWb s\n \n −1\n \n ✓\n
\n\n \n The student has plotted error bars for the potential difference. Outline why no error bars are shown for the current.\n \n
\n\n [1]\n
\n\n \n Δ\n \n I\n \n is too small to be shown/seen\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n Error bar of negligible size compared to error bar in\n \n V\n \n ✔\n \n
\n\n Almost all candidates realised that the uncertainty in I was too small to be shown. A common mistake was to mention that since I is the independent variable the uncertainty is negligible.\n
\n\n \n The expected value of\n \n \n \n \n \n is\n \n . Comment on your result\n \n .\n
\n\n [1]\n
\n\n \n Experimental value matches this/correct, as expected value within the range\n \n \n ✓\n
\n \n \n \n \n OR\n \n \n
\n \n \n experimental value does not match/incorrect, as it is not within range\n \n \n ✓\n \n
\n The torque is removed. The bar comes to rest in\n \n complete rotations with constant angular deceleration. Determine the time taken for the bar to come to rest.\n
\n\n [2]\n
\n\n \n \n \n \n OR\n \n \n \n ✓\n \n
\n\n \n ✓\n
\n\n
\n\n \n \n Other methods are possible.\n \n \n
\n\n \n \n Allow\n \n \n \n \n \n if\n \n used\n \n \n
\n\n \n \n Allow\n \n \n \n \n \n if\n \n used\n \n \n
\n\n \n \n Award\n \n \n \n [2]\n \n \n \n marks for a bald correct answer\n \n \n
\n\n Explain why the gas in configuration B has a greater number of microstates than in A.\n
\n\n [3]\n
\n\n Configuration A has only one microstate ✓\n
\n\n In configuration B, pairs of particles can be swapped between the halves ✓\n
\n\n Every such change gives rise to a new microstate «so there is a large number of microstates in B» ✓\n
\n\n The top of the wall is 2.4 m above the ground. Deduce whether the ball will hit the wall.\n
\n\n [3]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n ball does not hit wall\n \n \n OR\n \n \n 2.5 «m» > 2.4 «m»\n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from (b)(i) and from\n \n MP1\n \n \n
\n \n Allow g = 10 m s\n \n −2\n \n \n
\n\n For the propellor,\n \n and\n \n .\n
\n\n Calculate the moment of inertia of the propellor.\n
\n\n [1]\n
\n\n \n ✓\n
\n\n \n does support the photon nature of light.\n \n
\n\n [2]\n
\n\n \n «in the photon theory of light» the electron interacts with a single photon ✔\n
\n and absorbs all the energy\n \n \n OR\n \n \n and can leave the metal immediately ✔\n
\n \n
\n \n \n NOTE: Reference to photon-electron collision scores MP1\n \n \n
\n\n State the value of the resultant force on the aircraft when hovering.\n
\n\n [1]\n
\n\n \n zero\n \n \n ✓\n \n
\n\n This was generally answered well with the most common incorrect answer being the weight of the aircraft and package. The question uses the command term 'state' which indicates that the answer requires no working.\n
\n\n Sound of frequency 2400 Hz is emitted from a stationary source towards the oscillating plate in (b). The speed of sound is 340 m s\n \n −1\n \n .\n
\n\n \n
\n Determine the maximum frequency of the sound that is received back at the source after reflection at the plate.\n
\n\n
\n\n [2]\n
\n\n frequency at plate\n \n «\n \n Hz»\n
\n\n at source\n \n «Hz» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Award\n \n [1]\n \n mark when the effect is only applied once.\n \n
\n\n the angular impulse delivered to the disc and to the ring during the first 5.0 s.\n
\n\n [2]\n
\n\n The angular impulse is the product of torque and time ✓\n
\n\n Both factors are the same so the angular impulse is the same ✓\n
\n\n The half-life of a radioactive nuclide is 8.0 s. The initial activity of a pure sample of the nuclide is 10 000 Bq. What is the approximate activity of the sample after 4.0 s?\n
\n\n A. 2500 Bq\n
\n\n B. 5000 Bq\n
\n\n C. 7100 Bq\n
\n\n D. 7500 Bq\n
\n\n [1]\n
\n\n C\n
\n\n Roughly half of candidates (incorrectly) selected response D, without recognizing that the change in activity over time is not linear.\n
\n\n The liquid now freezes so that the vertical column is entirely of ice. Suggest how your answer to (a)(ii) will change.\n
\n\n [2]\n
\n\n the solid cannot now move relative to material above it ✓\n
\n\n so conduction only ✓\n
\n\n A sound wave travels through a gas at a speed of 270 m s\n \n −1\n \n . The graph shows the variation of the displacement\n \n s\n \n of the gas particles with distance\n \n d\n \n from the source.\n
\n\n \n
\n What is the frequency of the wave?\n
\n\n
\n A. 180 Hz\n
\n B. 360 Hz\n
\n\n C. 450 Hz\n
\n\n D. 900 Hz\n
\n\n [1]\n
\n\n A\n
\n\n Deduce the value of\n \n g\n \n and its absolute uncertainty for this experiment.\n
\n\n [2]\n
\n\n \n g\n \n = 9.996 «m s\n \n −2\n \n »\n \n \n OR\n \n \n Δ\n \n g =\n \n 4.20 «m s\n \n −2\n \n » ✔\n
\n\n \n g\n \n = (10 ± 4) «m s\n \n −2\n \n »\n
\n\n \n \n OR\n \n \n
\n\n \n g\n \n = (10.0 ± 4.2) «m s\n \n −2\n \n » ✔\n
\n\n \n Award\n \n [1]\n \n max for not proper significant digits or decimals use, such as: 9.996±4.178 or 10±4.2 or 10.0±4 or 10.0±4.18« m s\n \n −2\n \n »\n \n .\n
\n\n Many average candidates did not use the correct number of significant figures and wrote the answers inappropriately. Only the best candidates rounded out and wrote the proper answer of 10±4 ms\n \n −2\n \n . Some candidates did not propagate uncertainties and only compared the average calculated value with the known value 9.81 ms\n \n −2\n \n .\n
\n\n Calculate the percentage error in the measured value of\n \n g\n \n .\n
\n\n [3]\n
\n\n error in\n \n m\n \n \n 1\n \n +\n \n m\n \n \n 2\n \n is 1 %\n \n \n OR\n \n \n error in\n \n m\n \n \n 1\n \n −\n \n m\n \n \n 2\n \n is 40 %\n \n \n OR\n \n \n error in\n \n a\n \n is 1 % ✔\n
\n\n adds percentage errors ✔\n
\n\n so error in g is 42 %\n \n \n OR\n \n \n 40 %\n \n \n OR\n \n \n 41.8 % ✔\n
\n\n \n Allow answer 0.42 or 0.4 or 0.418.\n \n
\n\n \n Award\n \n [0]\n \n for comparing the average value with a known value, e.g. 9.81 m s-2\n \n .\n
\n\n Atwoods machine a) is a quite straightforward question that tests the ability to propagate uncertainties through calculations. Almost all candidates proved the ability to add percentages or relative calculations, however, many weaker candidates failed in the percentage uncertainty when subtracting the two masses.\n
\n\n Determine\n \n A\n \n by drawing the line of best fit.\n
\n\n [3]\n
\n\n a best-fit line drawn through the entire range of the data ✓\n
\n\n large triangle greater than half a line or two data points on the line greater than half a line apart ✓\n
\n\n correct read offs consistent with the line,\n \n eg\n \n \n ✓\n
\n\n \n Accept answer in the range 3.8–4.2\n \n
\n\n The graph shows the actual variation with displacement\n \n from M of the intensity of the light on the screen.\n \n is the intensity of light at the screen from one slit only.\n
\n\n \n
\n
\n\n The amplitude «at\n \n x\n \n = 0» will be doubled ✓\n
\n\n intensity is proportional to amplitude squared /\n \n ∝\n \n A\n \n \n 2\n \n ✓\n
\n\n \n Calculate the average power delivered to the ball during the impact.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n \n
\n\n \n \n \n \n \n ✔\n \n \n
\n\n \n \n \n \n \n »\n \n ✔\n \n \n \n
\n\n
\n\n \n \n \n \n ALTERNATIVE 2\n \n \n \n \n
\n\n \n \n \n \n \n ✔\n \n \n
\n\n \n \n \n \n »\n \n ✔\n \n \n
\n\n
\n\n This was well answered although a significant number of candidates approached it using P = Fv but forgot to divide v by 2 to calculated the average velocity. This scored one mark out of 2.\n
\n\n Calculate the maximum temperature of the gas during the cycle.\n
\n\n [3]\n
\n\n Correct read offs of pressure and volume at B ✓\n
\n\n \n ✓\n
\n\n \n «K» ✓\n
\n\n A variable resistor is connected in series to a cell with internal resistance\n \n r\n \n as shown.\n
\n\n \n
\n The resistance of the variable resistor is increased. What happens to the power dissipated in the cell and to the terminal potential difference of the cell?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n Ball 1 is dropped from rest from an initial height\n \n . At the same instant, ball 2 is launched vertically upwards at an initial velocity\n \n .\n
\n\n \n
\n At what time are both balls at the same distance above the ground?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n This question turned out to be challenging especially to SL candidates, and the number of blank answers was higher than expected. The most efficient way of solving it is by equating algebraic expressions for the height of each ball as a function of time, e.g.\n \n , followed by cancellation of the quadratic term.\n
\n\n The resistance of the loop is 2.4 Ω. Calculate the magnitude of the magnetic force on the loop as it enters the region of magnetic field.\n
\n\n [2]\n
\n\n \n \n \n OR\n \n \n \n «A» ✓\n
\n\n \n «N» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (c)(i)\n \n .\n \n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n the main source of error in\n \n T\n \n .\n
\n\n [1]\n
\n\n student’s reaction time «in starting and stopping stopwatch» / starting/stopping stopwatch ✓\n
\n\n Show that the net torque on the system about the central axis is approximately 30 N m.\n
\n\n [1]\n
\n\n \n = 50 × 0.5 + 40 × 0.2\n
\n\n \n \n OR\n \n \n
\n\n 33 «Nm» ✓\n
\n\n
\n\n \n Accept opposite rotational sign convention\n \n
\n\n \n A third-harmonic standing wave of wavelength 0.80 m is set up on a string fixed at both ends. Two points on the wave are separated by a distance of 0.60 m. What is a possible phase difference between the two points on the wave?\n \n
\n\n \n A.\n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n
\n\n [1]\n
\n\n C\n
\n\n This question had a low discrimination index with response D the most popular and an even spread between the other 3 answers. A third-harmonic standing wave of wavelength 0.8m must be on a string of length 1.2m giving 3 loops of 0.4m each. Depending on where the initial point is chosen, two points separated by 0.6m will either be in adjacent loops e.g. at 0.1m and 0.7 m with a phase difference of π or in the two end loops e.g at 0.3 m and 0.9m with a phase difference of 0. So for a standing wave there are only two possible answers, π (response C) or 0 (not included in these responses).\n
\n\n \n Suggest why de Broglie’s hypothesis is\n \n not\n \n consistent with Bohr’s conclusion that the electron’s orbit in the hydrogen atom has a well defined radius.\n \n
\n\n [2]\n
\n\n \n «de Broglie’s hypothesis states that the» electron is represented by a wave ✔\n
\n \n
\n \n therefore it cannot be localized/it is spread out/it does not have a definite position ✔\n \n
\n\n \n \n \n Award MP1 for any mention of wavelike property of an electron.\n \n \n \n
\n\n This question could have simply asked for the differences but did not puzzle the students who, when scoring, referred successfully to the differences between Bohr's postulate and de Broglie quantification of the wave like characteristics. Examiners marked this question without reference to particular physicist or what individuals suggested. As a result many scored the first mark for suggesting that electrons have wave like properties. The rest of the answers then commonly restated the stem of the question about a well-defined radius.\n
\n\n using a light source with a smaller wavelength.\n
\n\n [1]\n
\n\n gradient smaller\n \n ✓\n \n
\n\n Player B intercepts the ball when it is at its peak height. Player B holds a paddle (racket) stationary and vertical. The ball is in contact with the paddle for 0.010 s. Assume the collision is elastic.\n
\n\n \n
\n Calculate the average force exerted by the ball on the paddle. State your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n \n «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n 5.67 «N»\n \n ✓\n \n
\n\n any answer to 2 significant figures «N»\n \n ✓\n \n
\n\n Calculations using the data of the experiment show that\n \n g\n \n = 9.71622 m s\n \n −2\n \n with a percentage uncertainty of 8 %. Determine the value of\n \n g\n \n that can be obtained from this experiment. Include the absolute uncertainty in\n \n g\n \n to one significant figure.\n
\n\n [2]\n
\n\n \n g\n \n = 9.7 «m s\n \n −2\n \n » ✓\n
\n\n Δ\n \n g\n \n = 0.8 «m s\n \n −2\n \n » ✓\n
\n\n State the nature and direction of the force that accelerates the 15 kg object.\n
\n\n [1]\n
\n\n static friction force «between blocks»\n
\n\n \n \n AND\n \n \n
\n\n directed to the right ✓\n
\n\n The mass of the cylinder is\n \n and the cross-sectional area of the cylinder is\n \n . The density of water is\n \n . Show that the angular frequency of oscillation of the cylinder is about\n \n .\n
\n\n [2]\n
\n\n \n Evidence of equating\n \n «to obtain\n \n » ✓\n \n
\n\n
\n\n \n \n \n \n OR\n \n \n \n ✓\n \n
\n\n
\n\n \n \n Answer to at least\n \n s.f.\n \n \n
\n\n Again, very well answered.\n
\n\n Three statements about Boltzmann’s constant\n \n k\n \n \n B\n \n are:\n
\n\n I.\n \n k\n \n \n B\n \n has a unit of J K\n \n −1\n \n
\n\n II.\n \n k\n \n \n B\n \n \n
\n\n III.\n \n k\n \n \n B\n \n \n
\n\n Which statements are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n A\n
\n\n Why are high voltages and low currents used when electricity is transmitted over long distances?\n
\n\n A. Cables can be closer to the ground.\n
\n\n B. Electrons have a greater drift speed.\n
\n\n C. Energy losses are reduced.\n
\n\n D. Resistance of the power lines is reduced.\n
\n\n [1]\n
\n\n C\n
\n\n Outline one reason why this model of a dancer is unrealistic.\n
\n\n [1]\n
\n\n one example specified\n \n eg\n \n friction, air resistance, mass distribution not modelled ✓\n
\n\n
\n\n \n \n Award [1]\n \n for any reasonable physical parameter that is not consistent with the model\n \n
\n\n Show that the energy released is about 18 MeV.\n
\n\n [2]\n
\n\n «𝜇» = 2.0141 + 3.0160 − (4.0026 + 1.008665) «= 0.0188 u»\n
\n\n \n \n OR\n \n \n
\n\n \n In\n \n MeV: 1876.13415 + 2809.404 − (3728.4219 + 939.5714475) ✓\n
\n\n = 0.0188 × 931.5\n \n \n OR\n \n \n = 17.512 «MeV» ✓\n
\n\n \n Must see either clear substitutions or answer to at least 3 s.f. for\n \n MP2\n \n .\n \n
\n\n \n An ideal gas is in a closed container. Which changes to its volume and temperature when taken together must cause a decrease in the gas pressure?\n \n
\n\n \n
\n [1]\n
\n\n D\n
\n\n Three statements about the products of nuclear fission are:\n
\n\n I. some of them are chemically toxic\n
\n II. they have a wide range of half-lives\n
\n III. they release additional energy when removed from the reactor\n
\n Which statements are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n The graph shows the variation with distance\n \n r\n \n of the electric potential\n \n V\n \n from a charge\n \n Q\n \n .\n
\n\n \n
\n What is the electric field strength at distance s?\n
\n\n A. The area under the graph between s and infinity\n
\n\n B. The area under the graph between 0 and s\n
\n\n C. The gradient of the tangent at s\n
\n\n D. The negative of the gradient of the tangent at s\n
\n\n [1]\n
\n\n D\n
\n\n Calculate the work done during the increase in pressure.\n
\n\n [1]\n
\n\n \n \n «\n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Calculate the speed of the combined masses immediately after the collision.\n
\n\n [1]\n
\n\n 0.40 «m s\n \n −1\n \n » ✔\n
\n\n Outline, by reference to Newton’s third law, how the upward lift force on the aircraft is achieved.\n
\n\n [2]\n
\n\n \n Blades exert a downward force on the air\n \n \n ✓\n \n
\n\n \n
\n air exerts an equal and opposite force on the blades\n \n \n «\n \n \n by Newton’s third law\n \n \n »\n
\n \n \n \n \n OR\n \n \n
\n \n \n air exerts a reaction force on the blades\n \n \n «\n \n \n by Newton’s third law\n \n \n »\n \n \n ✓\n \n
\n \n \n
\n Downward direction required for\n \n \n \n MP1\n \n \n \n \n .\n \n
\n A rectangular coil rotates at a constant angular velocity. At the instant shown, the plane of the coil is at right angles to the line\n \n . A uniform magnetic field acts in the direction\n \n .\n
\n\n \n
\n What rotation of the coil about a specified axis will produce the graph of electromotive force (emf)\n \n against time\n \n ?\n
\n\n A. Through\n \n about\n \n
\n\n B. Through\n \n about\n \n
\n\n C. Through\n \n about\n \n
\n\n D. Through\n \n about\n \n
\n\n [1]\n
\n\n C\n
\n\n Protons can also be accelerated by the same potential difference\n \n U\n \n . Compare, without calculation, the de Broglie wavelength of the protons to that of the electrons.\n
\n\n [2]\n
\n\n The protons have the same energy but greater mass hence a greater momentum than the electrons ✓\n
\n\n From\n \n , the protons will have a shorter wavelength ✓\n
\n\n Two blocks, X and Y, are placed in contact with each other. Data for the blocks are provided.\n
\n\n \n
\n X has a mass\n \n \n \n . What is the mass of Y?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n This question was very well answered by candidates, reinforced by the high difficulty index for both HL and SL groups. This is another question that requires the rearrangement of an equation to determine a relationship between variables; interestingly candidates showed greater success on this question than others of this type. This may be due to the fact that there was not an easy distractor included in the response options, requiring candidates to work through equation substitution and rearrangement to reach a final answer.\n
\n\n The measurements of\n \n were collected five times. Explain how repeated measurements of\n \n reduced the random error in the final experimental value of\n \n .\n
\n\n [2]\n
\n\n \n mention of mean/average value «of\n \n \n \n \n \n »\n \n \n ✓\n \n
\n\n \n this reduces uncertainty in\n \n \n \n \n \n / result\n
\n \n \n \n \n OR\n \n \n
\n \n \n more accurate/precise\n \n \n ✓\n \n
\n
\n\n \n \n Reference to “random errors average out” scores MP1\n \n \n
\n\n \n \n Accept “closer to true value”, “more reliable value” OWTTE for MP2\n \n \n
\n\n
\n\n Most candidates stated that the mean of 5 values of\n \n T\n \n was used to obtain an answer closer to the true value if there were no systematic errors. Some just repeated the question.\n
\n\n A toy balloon floats at the end of a string. A wind blows horizontally to the right. The balloon is in translational equilibrium.\n
\n\n \n
\n What is the free-body diagram of the forces acting on the balloon?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n Three identical resistors of resistance R are connected as shown to a battery with a potential difference of\n \n and an internal resistance of\n \n . A voltmeter is connected across one of the resistors.\n
\n\n \n
\n What is the reading on the voltmeter?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n The slits are separated by a distance of 0.18 mm and the distance to the screen is 2.2 m. Determine, in m, the wavelength of light.\n
\n\n [2]\n
\n\n Use of\n \n s\n \n =\n \n =\n \n \n \n OR\n \n \n \n s\n \n =\n \n =\n \n ✓\n
\n\n \n = «\n \n =» 4.6 × 10\n \n −7\n \n «m» ✓\n
\n\n There is an advantage and a disadvantage in using two masses that are almost equal.\n
\n\n State and explain the advantage with reference to the magnitude of the acceleration that is obtained.\n
\n\n [2]\n
\n\n the acceleration would be small/the time of fall would be large ✔\n
\n\n easier to measure /a longer time of fall reduces the % error in the time of fall and «hence acceleration» ✔\n
\n\n \n Do not accept ideas related to the mass/moment of inertia of the pulley\n \n .\n
\n\n Q 1 b) was quite well answered. Only the weakest candidates presented difficulty in understanding simple mechanics.\n
\n\n Determine the mass of Mars.\n
\n\n [3]\n
\n\n Converts\n \n T\n \n to 27.6 ks\n \n and\n \n converts to m from Mm ✓\n
\n\n \n «s\n \n 2\n \n m\n \n −3\n \n » ✓\n
\n\n «\n \n »\n \n «kg» ✓\n
\n\n
\n\n \n MP1 can be implicit\n \n
\n\n Compare and contrast spontaneous and neutron-induced nuclear fission.\n
\n\n [2]\n
\n\n Spontaneous fission occurs with no external influence, neutron-induced fission requires an interaction with a neutron «of appropriate energy» ✓\n
\n\n Both result in the release of energy\n
\n \n \n OR\n \n \n
\n both have a large number of possible pairs of products ✓\n
\n A large stone is dropped from a tall building. What is correct about the speed of the stone after 1 s?\n
\n\n A. It is decreasing at increasing rate.\n
\n\n B. It is decreasing at decreasing rate.\n
\n\n C. It is increasing at increasing rate.\n
\n\n D. It is increasing at decreasing rate.\n
\n\n [1]\n
\n\n D\n
\n\n Estimate the specific latent heat of vaporization of water. State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n «\n \n mL = P\n \n t» so «\n \n » = 2.3 x 10\n \n 6\n \n «J kg\n \n -1\n \n »\n \n ✓\n \n
\n\n J kg\n \n −1\n \n \n ✓\n \n
\n\n A simple pendulum oscillates with frequency\n \n . The length of the pendulum is halved. What is the new frequency of the pendulum?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Two resistors of equal resistance R are connected with two cells of emf\n \n ε\n \n and 2\n \n ε\n \n . Both cells have negligible internal resistance.\n
\n\n \n
\n What is the current in the resistor labelled X?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n A sphere is suspended from the end of a string and rotates in a horizontal circle. Which freebody diagram, to the correct scale, shows the forces acting on the sphere?\n
\n\n \n
\n \n
\n [1]\n
\n\n D\n
\n\n Outline why the graph between P and O is negative.\n
\n\n [2]\n
\n\n The gravitational field is attractive so that energy is required «to move away from P» ✓\n
\n\n the gravitational potential is defined as 0 at\n \n , (the potential must be negative) ✓\n
\n\n the work function of the surface, in eV.\n
\n\n [2]\n
\n\n Use of\n \n E\n \n \n max\n \n =\n \n \n E\n \n \n max\n \n ✓\n
\n\n \n «\n \n −\n \n E\n \n \n max\n \n =\n \n − 1.81» = 0.85625\n \n 0.86 «eV» ✓\n
\n\n
\n\n Explain, by reference to Faraday’s law of induction, how an electromotive force (emf) is induced in the coil.\n
\n\n [3]\n
\n\n \n there is a magnetic flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n in the coil / coil cuts magnetic field\n \n \n ✓\n \n
\n\n \n this flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n changes as the angle varies/coil rotates\n \n \n ✓\n \n
\n\n \n «\n \n \n Faraday’s law\n \n \n »\n \n \n connects induced emf with rate of change of flux\n \n \n «\n \n \n linkage\n \n \n »\n \n \n with time\n \n \n ✓\n \n
\n\n \n \n
\n Do not award MP2 or 3 for answers that don’t discuss flux.\n \n \n
\n This question was well answered with the majority discussing changes in flux rather than wires cutting field lines, which was good to see.\n
\n\n Planets X and Y move in circular orbits around the same star.\n
\n\n The orbital period of planet Y is twice the orbital period of planet X. The orbital radius of planet X is\n \n \n \n .\n
\n\n What is the orbital radius of planet Y?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n A book is at rest on a table. One of the forces acting on the book is its weight.\n
\n\n What is the other force that completes the force pair according to Newton’s third law of motion?\n
\n\n A. The pull of the book on Earth\n
\n\n B. The pull of Earth on the book\n
\n\n C. The push of the table on the book\n
\n\n D. The push of the book on the table\n
\n\n [1]\n
\n\n A\n
\n\n The majority of candidates incorrectly selected option C for this question, resulting in a low difficulty index overall. This question highlights a typical misconception relating to Newton's 3rd law, and emphasises the importance of conceptual physics teaching.\n
\n\n Outline how an emf is generated in the coil.\n
\n\n [2]\n
\n\n The magnetic field moves relative to the coil ✓\n
\n\n As field lines cut the coil, forces act on (initially stationary) electrons in the wire (and these move producing an emf) ✓\n
\n\n A black body is on the Moon’s surface at point A. Show that the maximum temperature that this body can reach is 400 K. Assume that the Earth and the Moon are the same distance from the Sun.\n
\n\n [2]\n
\n\n \n T\n \n =\n \n \n \n \n \n ✔\n
\n\n 390 «K» ✔\n
\n\n \n Must see 1360 (from data booklet) used for MP1.\n \n
\n\n \n Must see at least 2 s.f\n \n .\n
\n\n Many candidates struggled with this question. A significant portion attempted to apply Wein’s Law and simply stated that a particular wavelength was the peak and then used that to determine the temperature. Some did use the solar constant from the data booklet and were able to calculate the correct temperature. As part of their preparation for the exam candidates should thoroughly review the data booklet and be aware of what constants are given there. As with all “show that” questions candidates should be reminded to include an unrounded answer.\n
\n\n Show that the wavelength of an electron in the beam is about\n \n .\n
\n\n [1]\n
\n\n \n \n \n \n OR\n \n \n \n ✓\n \n
\n\n \n \n
\n Answer to at least\n \n s.f. (i.e. 3.0)\n \n \n
\n An easy calculation with only one energy conversion to consider and a 'show' answer to help.\n
\n\n The graph below shows the variation with time of the magnetic flux through a coil.\n
\n\n \n
\n Which of the following gives three times for which the magnitude of the induced emf is a maximum?\n
\n\n A. 0,\n \n \n \n ,\n \n \n \n
\n\n B. 0,\n \n \n \n ,\n \n T\n \n
\n\n C. 0,\n \n \n \n ,\n \n T\n \n
\n\n D.\n \n \n \n ,\n \n \n \n ,\n \n \n \n
\n\n [1]\n
\n\n B\n
\n\n This question was extremely well done, with the highest difficulty index seen on this paper.\n
\n\n Determine the minimum area of the solar heating panel required to increase the temperature of all the water in the tank to 30°C during a time of 1.0 hour.\n
\n\n [3]\n
\n\n energy required = 250 × 4200 × (30 − 15) ✓\n
\n\n energy available = 0.30 × 680 ×\n \n t\n \n ×\n \n A\n \n ✓\n
\n\n \n A\n \n = «\n \n » 21 «m\n \n 2\n \n »\n \n \n OR\n \n \n 22 «m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Accept the correct use of 0.30 in either\n \n MP1\n \n or\n \n MP2\n \n .\n \n
\n\n Most candidates had a good attempt at this but there were often slight slips. Some missed the efficiency of the process. Some included the albedo of the roof tiles. Some thought that the temperature rise needed to have 273 added to convert to kelvin. However, sometimes scoring through ECF (error carried forward), the average mark was around 2 marks.\n
\n\n The work done to move a particle of charge 0.25 μC from one point in an electric field to another is 4.5 μJ. Calculate the magnitude of the potential difference between the two points.\n
\n\n [1]\n
\n\n «\n \n » 18 «V» ✓\n
\n\n \n Calculate, in eV, the work function of the metal surface.\n \n
\n\n [3]\n
\n\n \n \n ✔\n \n
\n\n \n \n ✔\n \n
\n\n \n \n \n ✔\n \n \n
\n\n \n \n \n \n NOTE: Allow reading from the graph of\n \n leading to an answer of 1.2 «eV».\n \n \n \n \n
\n\n The decay constant,\n \n , of a radioactive sample can be defined as\n
\n\n A. the number of disintegrations in the radioactive sample.\n
\n\n B. the number of disintegrations per unit time in the radioactive sample.\n
\n\n C. the probability that a nucleus decays in the radioactive sample.\n
\n\n D. the probability that a nucleus decays per unit time in the radioactive sample.\n
\n\n [1]\n
\n\n D\n
\n\n This question was well answered by HL candidates.\n
\n\n Outline why radiation B gives different results.\n
\n\n [1]\n
\n\n Identifies P work function lower than Q work function\n \n ✓\n \n
\n\n Determine the recoil velocity of the cannon.\n
\n\n [3]\n
\n\n Momentum must be conserved in initial direction of shell (20° above horizontal) ✓\n
\n\n Recoil velocity is 4.2 m s\n \n −1\n \n at 20° below horizontal ✓\n
\n\n 3.95 m s\n \n −1\n \n ✓\n
\n\n Calculate the absolute uncertainty in\n \n for Δ\n \n p\n \n = 30 kPa. State an appropriate number of significant figures for your answer.\n
\n\n [3]\n
\n\n 15 % seen anywhere ✓\n
\n\n «Δ(\n \n F\n \n \n 3\n \n ) =» 39.4 × 10\n \n 5\n \n × 0.15 = 5.9 × 10\n \n 5\n \n ✓\n
\n\n ±6 × 10\n \n 5\n \n ✓\n
\n\n \n \n
\n MP1\n \n is for the propagation of 5 %. It can be shown differently, e.g. 3 × 5% Allow students to use 40 × 10\n \n 5\n \n (from the graph).\n \n
\n \n Award\n \n MP3\n \n for\n \n any\n \n uncertainty rounded to 1 significant digit\n \n
\n\n \n \n Award [3]\n \n for a\n \n BCA\n \n .\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n \n
\n\n Determine\n \n . State your answer to an appropriate number of significant figures.\n
\n\n [3]\n
\n\n \n «\n \n \n lift force/change of momentum in one second\n \n \n »\n \n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n \n \n AND\n \n \n \n \n answer expressed to\n \n sf only\n \n \n ✓\n \n
\n\n \n \n
\n Allow\n \n \n \n from\n \n \n \n .\n
\n This was answered well with many getting full marks. A small number gave the wrong number of significant figures and some attempted to answer using kinematics equations or kinetic energy.\n
\n\n Which is correct for a black-body radiator?\n
\n\n
\n A. The power it emits from a unit surface area depends on the temperature only.\n
\n B. It has an albedo of 1.\n
\n\n C. It emits monochromatic radiation whose wavelength depends on the temperature only.\n
\n\n D. It emits radiation of equal intensity at all wavelengths.\n
\n\n [1]\n
\n\n A\n
\n\n \n Calculate the ratio\n \n \n \n .\n \n
\n\n [1]\n
\n\n «\n \n \n \n \n »\n \n \n \n ✔\n \n
\n\n This was well answered with the most common mistake being to use the volume of a single atom rather than the total volume of the atoms.\n
\n\n Calculate the thermal energy (heat) taken out of the gas from B to C.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n ✓\n
\n\n \n «\n \n × 3.33 × 10\n \n −2\n \n × (3.00 × 10\n \n 4\n \n − 4.60 × 10\n \n 3\n \n )» = 1268.7 ≈ 1270 «J» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n .\n \n
\n\n \n Accept negative values.\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n \n \n OR\n \n \n \n T\n \n c\n \n \n = 4.6 × 10\n \n 3\n \n × 3.33 × 10\n \n −2\n \n × 1.66 = 92.2 ✓\n
\n\n \n «J» ✓\n
\n\n
\n\n \n Award\n \n MP1\n \n if T\n \n c\n \n = 92 taken from\n \n (e)\n \n \n
\n\n Identify with ticks [✓] in the table, the forces that can act on electrons and the forces that can act on quarks.\n
\n\n \n
\n [2]\n
\n\n Weak nuclear: 2 ticks ✓\n
\n Strong nuclear: quarks only ✓\n
\n An object moves in a circle of constant radius. Values of the centripetal force\n \n are measured for different values of angular velocity\n \n . A graph is plotted with\n \n on the\n \n -axis. Which quantity plotted on the\n \n -axis will produce a straight-line graph?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n Outline why the pattern observed on the screen is an evidence for matter waves.\n
\n\n [2]\n
\n\n The pattern is formed when the electrons scattered from adjacent planes in the graphite crystal undergo interference / diffract ✓\n
\n\n Interference / diffraction is a property of waves only ✓\n
\n\n A layer of ice on the surface of a lake separates cold air from relatively warmer unfrozen water.\n
\n\n \n
\n The temperature of the air and the temperature of the water can both be assumed constant. The thickness of the ice gradually increases. What effect does the change in ice thickness have on the temperature gradient across the ice and the rate of thermal energy transfer by conduction through the ice?\n
\n\n
\n| \n | \n\n \n Temperature gradient across the ice\n \n | \n\n \n Rate of thermal energy transfer through the ice\n \n | \n
| \n A.\n | \n\n increases\n | \n\n increases\n | \n
| \n B.\n | \n\n increases\n | \n\n decreases\n | \n
| \n C.\n | \n\n decreases\n | \n\n increases\n | \n
| \n D.\n | \n\n decreases\n | \n\n decreases\n | \n
\n [1]\n
\n\n D\n
\n\n Calculate the thermal energy transferred from the sample during the first\n \n minutes.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n
\n\n Discuss, for this process, the changes that occur in the internal energy of the gas.\n
\n\n [2]\n
\n\n internal energy is constant ✓\n
\n\n
\n internal energy depends on kinetic energy/temperature «only»\n
\n \n \n OR\n \n \n
\n\n since temperature/kinetic energy is constant ✓\n
\n\n
\n\n \n Do not award\n \n MP2\n \n for stating that “temperature is constant” unless linked to the correct conclusion, as that is mentioned in the stem.\n \n
\n\n \n Award\n \n MP2\n \n for stating that kinetic energy remains constant.\n \n
\n\n A balloon rises at a steady vertical velocity of\n \n . An object is dropped from the balloon at a height of\n \n above the ground. Air resistance is negligible. What is the time taken for the object to hit the ground?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Even though over half the candidates are choosing the correct response it has a low discrimination index. Many are choosing D indicating that they forgot to take the velocity upward as negative.\n
\n\n Outline why component X is considered non-ohmic.\n
\n\n [1]\n
\n\n \n current is not «directly» proportional to the potential difference\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X is not constant\n
\n \n \n \n \n OR\n \n \n
\n \n \n resistance of X changes «with current/voltage»\n \n \n ✓\n \n
\n Which law is equivalent to the law of conservation of energy?\n
\n\n
\n A. Coulomb’s law\n
\n B. Ohm’s Law\n
\n\n C. Newton’s first law\n
\n\n D. Lenz’s law\n
\n\n [1]\n
\n\n D\n
\n\n \n Calculate, in m s\n \n –1\n \n , the speed for this wave.\n \n
\n\n [1]\n
\n\n \n v =\n \n \n «\n \n » 250 «m s\n \n –1\n \n »✔\n \n
\n\n Calculate, for the surface of\n \n , the gravitational field strength\n \n g\n \n \n Io\n \n due to the mass of\n \n . State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n N kg\n \n −1\n \n \n \n OR\n \n \n m s\n \n −2\n \n \n ✓\n \n
\n\n Four particles, two of charge +Q and two of charge −Q, are positioned on the\n \n -axis as shown. A particle P with a positive charge is placed on the\n \n -axis. What is the direction of the net electrostatic force on this particle?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n Star X has a luminosity\n \n L\n \n and an apparent brightness\n \n b\n \n . Star X is at a distance\n \n \n \n from Earth.\n
\n\n Star Y has the same apparent brightness as X but is four times more luminous.\n
\n\n What is the distance of Star Y from Earth?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n State how energy is transferred from the inside of the metal pipe to the outside of the metal pipe.\n
\n\n [1]\n
\n\n conduction/conducting/conductor «through metal» ✓\n
\n\n Many candidates recognized that heat transfer by conduction was the correct response. This was a \"state\" question, so candidates were not required to go beyond this.\n
\n\n The ball leaves the ground at an angle of 22°. The horizontal distance from the initial position of the edge of the ball to the wall is 11 m. Calculate the time taken for the ball to reach the wall.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n \n
\n\n The Hertzsprung–Russell diagram shows two stars,\n \n and\n \n .\n
\n\n \n
\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C. 4\n
\n\n D. 16\n
\n\n [1]\n
\n\n A\n
\n\n \n Show that the pressure at B is about 130 kPa.\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n = 127 kPa\n \n ✔\n \n
\n\n The graph shows the variation with time\n \n t\n \n of the velocity of an object.\n
\n\n \n
\n What is the variation with time\n \n t\n \n of the acceleration of the object?\n
\n
\n
\n \n
\n [1]\n
\n\n A\n
\n\n A beam of X-rays of wavelength 100.00 pm is scattered from a block of carbon. Radiation is observed at right angles to the incident beam.\n
\n\n What is the Compton shift for the observed radiation?\n
\n\n
\n A. 0.1024 pm\n
\n B. 2.4322 pm\n
\n\n C. 2.4322 nm\n
\n\n D. 0.1024 nm\n
\n\n [1]\n
\n\n B\n
\n\n State and explain the effect of the angular impulse on the body of the aeroplane.\n
\n\n [2]\n
\n\n As the motor is internal, angular momentum is conserved (ignoring the torques due to resistive forces) ✓\n
\n\n The body of the plane will (try to) rotate in the opposite direction to the propellor ✓\n
\n\n Draw an arrow on the diagram to represent the direction of the acceleration of the satellite.\n
\n\n [1]\n
\n\n arrow normal to the orbit towards the Earth ✓\n
\n\n \n Identify the fundamental units of\n \n \n .\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n Accept\n \n \n \n
\n\n \n \n
\n\n Although the question was specifically about the fundamental units, several candidates lost the mark by answering Pa m.\n
\n\n When 40 kJ of energy is transferred to a quantity of a liquid substance, its temperature increases by 20 K. When 600 kJ of energy is transferred to the same quantity of the liquid at its boiling temperature, it vaporizes completely at constant temperature. What is\n
\n\n \n
\n\n for this substance?\n
\n\n A. 15 K\n \n −1\n \n
\n\n B. 15 K\n
\n\n C. 300 K\n \n −1\n \n
\n\n D. 300 K\n
\n\n [1]\n
\n\n D\n
\n\n \n Calculate the change in internal energy of the gas for the process A→B.\n \n
\n\n [2]\n
\n\n «use of\n \n \n \n \n and\n \n \n \n to give»\n \n
\n\n \n \n \n ✔\n
\n\n «\n \n \n \n \n »\n \n
\n\n \n =«–»375«J» ✔\n \n
\n\n \n \n Another method is possible: eg realisation that ΔU for BC has same magnitude, so ΔU = 3/2 PΔV.\n \n \n
\n\n Not very many candidates seem to know the generalised formula ΔU =1.5(P2V2 -P1V1) however many correct answers were seen.\n
\n\n State and explain, using your diagram, why a force acts on B due to A in the plane of the paper.\n
\n\n [3]\n
\n\n B lies in magnetic field of A OWTTE ✓\n
\n\n Explained use of appropriate rule together with drawn indication of rule operating in this case ✓\n
\n\n To show that force on B is to left and in plane of paper ✓\n
\n \n \n OR\n
\n \n \n Magnetic field lines of B merge with those of A to give combined field line pattern ✓\n
\n Sketch of combined pattern to show null point somewhere on line between wires. ✓\n
\n\n Wires will move to reduce stored energy and this is achieved by moving together so force on B is to left ✓\n
\n\n \n The diagram shows a resistor network. The potential difference between X and Y is 8.0 V.\n \n
\n\n \n \n \n
\n \n \n What is the current in the 5Ω resistor?\n \n \n
\n\n \n \n A. 1.0A\n
\n \n \n
\n \n \n B. 1.6A\n
\n \n \n
\n \n \n C. 2.0A\n
\n \n \n
\n \n \n D. 3.0A\n \n \n
\n\n [1]\n
\n\n A\n
\n\n The group obtains the following repeated readings for\n \n d\n \n for\n \n one\n \n value of\n \n W\n \n .\n
\n\n \n
\n The group divides into two subgroups, A and B, to analyse the data.\n
\n\n Group A quotes the mean value of\n \n d\n \n as 2.93 cm.\n
\n\n Group B quotes the mean value of\n \n d\n \n as 2.8 cm.\n
\n\n Discuss the values that the groups have quoted.\n
\n\n [2]\n
\n\n 3 sf is inappropriate for\n \n A\n \n ✓\n
\n\n rejects trial 3 as outlier for\n \n B\n \n ✓\n
\n\n State\n \n one\n \n source of the radioactive waste products from nuclear fission reactions.\n
\n\n [1]\n
\n\n Fission fragments from the fuel rods\n
\n\n \n OR\n \n activated materials in (e.g.) fuel rod casings\n
\n\n \n OR\n \n nuclei formed by neutron activation from U-235\n
\n\n \n OR\n \n stated products, e.g. Pu, U-236 etc. ✓\n
\n\n State the direction of the resultant electric field at P.\n
\n\n [1]\n
\n\n directed vertically up «on plane of the page» ✓\n
\n\n
\n\n \n Allow an arrow pointing up on the diagram.\n \n
\n\n An electric motor raises an object of weight\n \n through a vertical distance of\n \n in\n \n . The current in the electric motor is\n \n at a potential difference of\n \n . What is the efficiency of the electric motor?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Three possible features of an atomic model are\n
\n\n I. orbital radius\n
\n\n II. quantized energy\n
\n\n III. quantized angular momentum.\n
\n\n Which of these are features of the Bohr model for hydrogen?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II, and III\n
\n\n [1]\n
\n\n D\n
\n\n Calculate the theoretical equilibrium temperature of the mixture.\n
\n\n [3]\n
\n\n \n
\n\n \n
\n\n One heat capacity term correctly substituted ✓\n
\n\n latent heat correctly substituted\n \n ✓\n
\n\n \n «°C» ✓\n
\n\n Calculate the pressure of the gas at B.\n
\n\n [2]\n
\n\n use of\n \n pV\n \n = constant ✓\n
\n\n \n P\n \n \n B\n \n = 43 «Kpa» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n Fuel rods in a nuclear fission reactor contain uranium isotopes U-235 and U-238. Which process taking place in the reactor contributes most significantly to the formation of radioactive waste products?\n
\n\n
\n A. alpha decay of U-235\n
\n B. alpha decay of U-238\n
\n\n C. neutron-induced fission of U-235\n
\n\n D. neutron-induced transmutation of U-238 to plutonium-239\n
\n\n [1]\n
\n\n C\n
\n\n \n Sea waves move towards a beach at a constant speed of 2.0 m s\n \n –1\n \n . They arrive at the beach with a frequency of 0.10 Hz. A girl on a surfboard is moving in the sea at right angles to the wave fronts. She observes that the surfboard crosses the wave fronts with a frequency of 0.40 Hz.\n \n
\n\n \n \n \n
\n \n \n What is the speed of the surfboard and what is the direction of motion of the surfboard relative to the beach?\n \n \n
\n\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n Explain why the rate calculated in part (a) is decreasing.\n
\n\n [2]\n
\n\n The temperature gradient decreases as the water cools down ✓\n
\n\n The rate of energy transfer is proportional to the temperature gradient ✓\n
\n\n Element X has a nucleon number\n \n and a nuclear density\n \n . Element Y has a nucleon number of\n \n . What is an estimate of the nuclear density of element Y?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Three correct statements about the behaviour of electrons are:\n
\n\n I. An electron beam is used to investigate the structure of crystals.\n
\n II. An electron beam produces a pattern of fringes when sent through two narrow parallel slits.\n
\n III. Electromagnetic radiation ejects electrons from the surface of a metal.\n
\n Which statements are explained using the wave-like properties of electrons?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n A\n
\n\n State the value of the resultant force on the aircraft when hovering.\n
\n\n [1]\n
\n\n \n zero\n \n \n ✓\n \n
\n\n This was generally answered well with the most common incorrect answer being the weight of the aircraft and package. The question uses the command term 'state' which indicates that the answer requires no working.\n
\n\n A car accelerates uniformly from rest to a velocity\n \n \n \n during time\n \n . It then continues at constant velocity\n \n \n \n from\n \n to time\n \n .\n
\n\n What is the total distance covered by the car in\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n
\n C.\n \n
\n
\n D.\n \n
\n [1]\n
\n\n D\n
\n\n The ball leaves the ground at an angle of 22°. The horizontal distance from the initial position of the edge of the ball to the wall is 11 m. Calculate the time taken for the ball to reach the wall.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n \n
\n\n Between the first and second positions of maximum loudness, the tube is raised through 0.37 m. The speed of sound in the air in the tube is 320 m s\n \n −1\n \n . Determine the frequency of the sound emitted by the loudspeaker.\n
\n\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n Monochromatic light of wavelength 633 nm is normally incident on a diffraction grating. The diffraction maxima incident on a screen are detected and their angle\n \n θ\n \n to the central beam is determined. The graph shows the variation of sin\n \n θ\n \n with the order\n \n n\n \n of the maximum. The central order corresponds to\n \n n\n \n = 0.\n
\n\n \n
\n Determine a mean value for the number of slits per millimetre of the grating.\n
\n\n [4]\n
\n\n identifies gradient with\n \n \n \n OR\n \n \n use of\n \n \n ✓\n \n
\n\n gradient = 0.08\n \n \n OR\n \n \n correct replacement in equation with coordinates of a point\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from\n \n MP3\n \n \n
\n The molar mass of water is 18 g mol\n \n −1\n \n . Estimate the average speed of the water molecules in the vapor produced. Assume the vapor behaves as an ideal gas.\n
\n\n [2]\n
\n\n \n E\n \n \n k\n \n = «\n \n » =\n \n «J»\n \n ✓\n \n
\n\n \n v =\n \n «\n \n \n \n »\n \n =\n \n 720 «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n \n Calculate the average force exerted by the racquet on the ball.\n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n \n \n \n \n \n \n =\n \n \n \n 148«\n \n \n \n »≈150«\n \n \n \n \n \n » ✔\n \n
\n\n
\n\n At both HL and SL many candidates scored both marks for correctly answering this. A straightforward start to the paper. For those not gaining both marks it was possible to gain some credit for calculating either the change in momentum or the acceleration. At SL some used 64 ms-1 as a value for a and continued to use this value over the next few parts to the question.\n
\n\n Outline, with reference to the decay equation above, the role of chain reactions in the operation of a nuclear power station.\n
\n\n [3]\n
\n\n The four neutrons released in the reaction may initiate further fissions ✓\n
\n\n «If sufficient U-235 is available,» the reaction is self-sustained ✓\n
\n\n Allowing for the continuous production of energy ✓\n
\n\n The number of neutrons available is controlled with control rods «to maintain the desired reaction rate» ✓\n
\n\n Outline what is meant by one astronomical unit (1 AU)\n
\n\n [1]\n
\n\n «mean» Distance from centre of Sun to centre of Earth ✓\n
\n\n \n \n OR\n \n \n
\n\n Suitable ratio in terms of parsec and arcsecond ✓\n
\n\n The radius of a nucleus of\n \n is 7.1 × 10\n \n −15\n \n m. Explain why there will be no deviations from Rutherford scattering in the experiment in (b)(i).\n
\n\n [2]\n
\n\n The closest approach is «significantly» larger than the radius of the nucleus / far away from the nucleus/\n \n \n OWTTE\n \n \n . ✓\n
\n\n «Therefore» the strong nuclear force will not act on the alpha particle.✓\n
\n\n In a photoelectric experiment a stopping voltage\n \n \n \n required to prevent photoelectrons from flowing across the photoelectric cell is measured for light of two frequencies\n \n and\n \n . The results obtained are shown.\n \n
\n The ratio\n \n is an estimate of\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The escape speed from the surface of earth is\n \n v\n \n \n esc\n \n . The radius of earth is\n \n R\n \n . A satellite of mass m is in orbit at a height\n \n above the surface of the Earth. What is the energy required to move the satellite to infinity?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n A mass of 0.25 kg hangs from a spring of spring constant 4.0 N m\n \n −1\n \n .\n
\n\n What is the natural frequency of oscillation for this system?\n
\n\n
\n A. 0.50 Hz\n
\n B. 0.64 Hz\n
\n\n C. 1.6 Hz\n
\n\n D. 2.0 Hz\n
\n\n [1]\n
\n\n B\n
\n\n The moment of inertia of the rod about the axis is 0.180 kg m\n \n 2\n \n . Show that the moment of inertia of the rod–particle system is about 0.25 kg m\n \n 2\n \n .\n
\n\n [1]\n
\n\n 0.180 + 0.200 × 0.60\n \n 2\n \n «= 0.252 kg m\n \n 2\n \n » ✓\n
\n\n \n Calculate the temperature at A if the temperature at B is\n \n −\n \n 40°C.\n \n
\n\n [1]\n
\n\n \n \n T\n \n \n A\n \n = 816\n \n «\n \n \n K\n \n \n »\n \n \n \n OR\n \n \n 543«\n \n °C\n \n »\n \n \n \n ✔\n \n \n
\n\n The temperature at A was found correctly by most candidates.\n
\n\n \n During its evolution, the Sun is likely to be a red giant of surface temperature 3000 K and luminosity 10\n \n 4\n \n L\n \n \n \n ☉\n \n . Later it is likely to be a white dwarf of surface temperature 10 000 K and luminosity 10-4 L\n \n \n \n ☉\n \n . Calculate the\n \n \n \n .\n \n
\n\n [2]\n
\n\n \n
\n Calculating the ratio of the radius of a white dwarf to a red giant star was done quite well by most candidates. However quite a few candidates made POT errors or forgot to take the final square root.\n
\n\n Two spheres have the same positive charge. A point M is midway between the two spheres.\n
\n\n \n
\n Along the line joining the spheres, what is true about the electrical field and the electric potential at M?\n
\n\n
\n| \n | \n\n \n Electric field\n \n | \n\n \n Electric potential\n \n | \n
| \n A.\n | \n\n zero\n | \n\n minimum positive value\n | \n
| \n B.\n | \n\n maximum\n | \n\n minimum positive value\n | \n
| \n C.\n | \n\n zero\n | \n\n maximum positive value\n | \n
| \n D.\n | \n\n maximum\n | \n\n maximum positive value\n | \n
\n [1]\n
\n\n A\n
\n\n A ball is thrown vertically downwards with an initial speed of 4.0 m s\n \n −1\n \n . The ball hits the ground with a speed of 16 m s\n \n −1\n \n . Air resistance is negligible. What is the time of fall and what is the distance travelled by the ball?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n The Sankey diagram shows the energy transfers in a nuclear power station.\n
\n\n \n
\n Electrical power output of the power station is 1000 MW.\n
\n\n What is the thermal power loss in the heat exchanger?\n
\n\n
\n\n A. 500 MW\n
\n\n B. 1000 MW\n
\n\n C. 1500 MW\n
\n\n D. 2500 MW\n
\n\n [1]\n
\n\n B\n
\n\n Between the first and second positions of maximum loudness, the tube is raised through 0.37 m. The speed of sound in the air in the tube is 320 m s\n \n −1\n \n . Determine the frequency of the sound emitted by the loudspeaker.\n
\n\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n Outline how an approximate adiabatic change can be achieved.\n
\n\n [2]\n
\n\n \n adiabatic means no transfer of heat in or out of the system\n \n \n ✓\n \n
\n\n \n should be fast\n \n \n ✓\n \n
\n\n \n «can be slow if» the system is insulated\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n \n Calculate, in hours, the time at which the activity of the sample has decreased to one-third of the initial activity.\n \n
\n\n [2]\n
\n\n \n \n \n \n \n \n ✔\n
\n \n
\n \n \n t\n \n = 20«hr» ✔\n \n
\n\n This was very well answered with the majority of candidates scoring full marks. This is a good indication that candidates weren’t short of time in this paper.\n
\n\n Show that the internal resistance of the cell is about 0.7 Ω.\n
\n\n [2]\n
\n\n 29.4 (50.0 +\n \n r\n \n ) = 139 (10.0 +\n \n r\n \n ) ✓\n
\n\n
\n attempt to solve for\n \n r\n \n , e.g. 29.4 × 50.0 − 139 × 10.0 =\n \n r\n \n (139 − 29.4)\n
\n \n \n OR\n \n \n
\n\n 0.73 «Ω» ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow working backwards from 0.7 Ω.\n \n
\n\n Many answers here produced a number that did not round to 0.7 but students claimed it did. The simultaneous equation approach was seen in the best candidates, getting the right answer. It is worthy of reminding about the need of showing one more decimal place when calculating a show that value type of question.\n
\n\n \n undergoes an alpha decay, followed by a beta-minus decay. What is the number of protons and neutrons in the resulting nuclide?\n
\n\n \n
\n [1]\n
\n\n C\n
\n\n This question was generally well answered by candidates, however a significant number selected option A (incorrectly) perhaps due to confusion between nuclear mass and the number of neutrons. This question had a relatively high discrimination index.\n
\n\n Explain why star B has a greater surface area than star A.\n
\n\n [2]\n
\n\n stars have same/similar\n \n L\n \n \n \n AND\n \n \n star B has lower\n \n T\n \n ✓\n
\n\n correct reference to luminosity formula (\n \n L\n \n α\n \n AT\n \n \n 4\n \n ) ✓\n
\n\n
\n\n \n \n MP1\n \n Allow reverse argument i.e., star A has higher T\n \n
\n\n When a high-energy\n \n -particle collides with a beryllium-9 (\n \n ) nucleus, a nucleus of carbon\n \n may be produced. What are the products of this reaction?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n State\n \n one\n \n assumption of the kinetic model of an ideal gas.\n
\n\n [1]\n
\n\n particles can be considered points «without dimensions»\n \n ✓\n \n
\n\n no intermolecular forces/no forces between particles «except during collisions»\n \n ✓\n \n
\n\n the volume of a particle is negligible compared to volume of gas\n \n ✓\n \n
\n\n collisions between particles are elastic\n \n ✓\n \n
\n\n time between particle collisions are greater than time of collision\n \n ✓\n \n
\n\n no intermolecular PE/no PE between particles\n \n ✓\n \n
\n\n
\n\n \n Accept reference to atoms/molecules for “particle”\n \n
\n\n State how energy is transferred from the inside of the metal pipe to the outside of the metal pipe.\n
\n\n [1]\n
\n\n conduction/conducting/conductor «through metal» ✓\n
\n\n Many candidates recognized that heat transfer by conduction was the correct response. This was a \"state\" question, so candidates were not required to go beyond this.\n
\n\n An object is suspended from a spring balance. When the object is in air the spring balance reads 900 N. When the object is completely submerged in water the spring balance reads 400 N.\n
\n\n The density of water is 1000 kg m\n \n −3\n \n .\n
\n\n What is the volume of the object?\n
\n\n
\n A. 0.04 m\n \n 3\n \n
\n B. 0.05 m\n \n 3\n \n
\n\n C. 0.09 m\n \n 3\n \n
\n\n D. 0.5 m\n \n 3\n \n
\n\n [1]\n
\n\n B\n
\n\n Use the graph to show that the nuclear radius of silicon-30 is about 4 fm.\n
\n\n [3]\n
\n\n read off between 17 and 19 «deg» ✔\n
\n\n correct use of\n \n d\n \n =\n \n \n \n \n \n = 7.8 × 10\n \n −15\n \n «m» ✔\n
\n\n so radius =\n \n \n \n «fm» = 3.9 «fm» ✔\n
\n\n \n Award ecf for wrong angle in MP1.\n \n
\n\n \n Answer for MP3 must show at least 2\n \n \n sf.\n \n
\n\n This question was left blank by many candidates and many of those who attempted it chose an angle that when used with the correct equation gave an answer close to the given answer of 4 fm. Very few selected the correct angle, calculated the correct diameter, and divided by two to get the correct radius.\n
\n\n Outline why repeated measurements of\n \n would not reduce any systematic error in\n \n .\n
\n\n [1]\n
\n\n \n systematic errors «usually» constant/always present/ not influenced by repetition\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Usually very well answered acknowledging that systematic errors are constant and present throughout all measurements.\n
\n\n Two bodies collide on a horizontal frictionless surface. Body X, of mass 2.0 kg, moves with an initial speed of 0.80 m s\n \n \n −1\n \n \n and body Y is initially stationary. After the collision, body X moves at an angle of 90° to the initial direction of motion with a speed of 0.60 m s\n \n \n −1\n \n \n .\n
\n\n \n
\n What is the magnitude of the momentum of body Y after the collision?\n
\n\n
\n A. 0.40 kg m s\n \n \n −1\n \n \n
\n B. 1.0 kg m s\n \n \n −1\n \n \n
\n\n C. 2.0 kg m s\n \n \n −1\n \n \n
\n\n D. 2.8 kg m s\n \n \n −1\n \n \n
\n\n [1]\n
\n\n C\n
\n\n The graph shows how the position of an object varies with time in the interval from 0 to 3 s.\n
\n\n \n
\n At which point does the instantaneous speed of the object equal its average speed over the interval from 0 to 3 s?\n
\n\n [1]\n
\n\n C\n
\n\n Two charges, +Q and −Q, are placed as shown.\n
\n\n What is the magnitude of the electric field strength, in descending order, at points X, Y and Z.\n
\n\n \n
\n
\n\n A. YXZ\n
\n\n B. ZXY\n
\n\n C. ZYX\n
\n\n D. YZX\n
\n\n [1]\n
\n\n C\n
\n\n This question was well answered by candidates, with a high difficulty index.\n
\n\n Determine\n \n .\n
\n\n [2]\n
\n\n Work using\n \n g\n \n ∝\n \n ✓\n
\n\n \n = 0.75 ✓\n
\n\n Strontium-90 decays to Zirconium-90 via two successive beta emissions. Discuss whether all the energy released when strontium-90 decays to Zirconium-90 can be transferred to a thermal form.\n
\n\n [2]\n
\n\n (No)\n
\n (anti-)neutrinos are released in (both) decays ✓\n
\n Carrying away energy because they interact poorly with matter ✓\n
\n\n
\n\n \n Ignore arguments relating to energy transferred to nucleus as this appears eventually as thermal energy.\n \n
\n\n A beta-minus particle and an alpha particle have the same initial kinetic energy.\n
\n\n Outline why the beta-minus particle can travel further in air than the alpha particle.\n
\n\n [2]\n
\n\n Alphas have double charge «and so are better ionisers »✓\n
\n\n alphas have more mass and therefore slower «for same energy» ✓\n
\n\n so longer time/more likely to interact with the «atomic» electrons/atoms «and therefore better ionisers» ✓\n
\n\n \n Accept reverse argument in terms of betas travelling faster.\n \n
\n\n \n Calculate the binding energy per nucleon for uranium-238.\n \n
\n\n [3]\n
\n\n \n 234 × 7.6\n \n \n OR\n \n \n 4 × 7.07 ✔\n \n
\n\n \n BE\n \n \n U\n \n =\n \n \n « 234\n \n ×\n \n 7.6\n \n + 4 × 7.07 – 4.27 =\n \n »\n \n « MeV » ✔\n \n \n
\n\n \n \n \n \n « MeV » ✔\n \n \n \n
\n\n \n \n \n \n \n NOTE: Allow ECF from MP2\n
\n Award\n \n [3]\n \n for bald correct answer\n
\n Allow conversion to J, final answer is 1.2\n \n ×\n \n 10\n \n –12\n \n \n \n \n \n \n
\n A gas storage tank of fixed volume\n \n V\n \n contains\n \n N\n \n molecules of an ideal gas at temperature\n \n T\n \n . The pressure at kelvin temperature\n \n T\n \n is 20 MPa.\n \n \n \n \n \n molecules are removed and the temperature changed to 2\n \n T\n \n . What is the new pressure of the gas?\n
\n\n A. 10 MPa\n
\n\n B. 15 MPa\n
\n\n C. 30 MPa\n
\n\n D. 40 MPa\n
\n\n [1]\n
\n\n C\n
\n\n proton number.\n
\n\n [1]\n
\n\n 2 ✓\n
\n\n Another black body is on the Moon’s surface at point B.\n
\n\n Outline, without calculation, why the aximum temperature of the black body at point B is less than at point A.\n
\n\n [2]\n
\n\n energy/Power/Intensity lower at B ✔\n
\n\n connection made between energy/power/intensity and temperature of blackbody ✔\n
\n\n This is question is another example of candidates not thinking beyond the obvious in the question. Many simply said that point B is farther away, or that it is at an angle. Some used vague terms like “the sunlight is more spread out” rather than using proper physics terms. Few candidates connected the lower intensity at B with the lower temperature of the blackbody.\n
\n\n Determine the angle\n \n θ\n \n that the velocity of ball B makes with the initial direction of motion of ball A.\n
\n\n [3]\n
\n\n The use of conservation of momentum in the horizontal direction, e.g.\n \n ✓\n
\n\n \n «\n \n »\n \n «m s\n \n −1\n \n » ✓\n
\n\n \n ✓\n
\n\n Calculate the work done during the increase in pressure.\n
\n\n [1]\n
\n\n \n \n «\n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n Calculate the pressure following this process.\n
\n\n [2]\n
\n\n \n use of\n \n is constant «\n \n »\n \n \n ✓\n \n
\n\n \n \n \n \n OR\n \n \n \n «\n \n »\n \n \n ✓\n \n
\n\n
\n\n \n \n Award\n \n \n \n [2]\n \n \n \n marks for a bald correct answer\n \n \n
\n\n Which statement is correct about Compton scattering of a photon by an electron?\n
\n\n
\n A. The energy of the photon decreases.\n
\n B. The wavelength of the photon decreases.\n
\n\n C. The momentum of the photon is unchanged.\n
\n\n D. The combined momentum of the particles increases.\n
\n\n [1]\n
\n\n A\n
\n\n The work done during the isothermal expansion A → B is 540 J. Calculate the thermal energy that leaves the gas during one cycle.\n
\n\n [2]\n
\n\n heat into gas «is along AB» and equals\n
\n\n \n Q\n \n in\n \n \n «= Δ\n \n U\n \n +\n \n W\n \n = 0 + 540» = 540 «J» ✔\n
\n\n heat out is (1−\n \n e\n \n )\n \n Q\n \n in =\n \n \n (1−0.45) × 540 = 297 «J» ≈ 3.0 × 10\n \n 2\n \n «J» ✔\n
\n\n \n Award\n \n [2]\n \n for bald correct answer.\n \n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n Outline the cause of the electron emission for radiation A.\n
\n\n [1]\n
\n\n photon transfers «all» energy to electron\n \n ✓\n \n
\n\n State and explain the magnitude of the force on a length of 0.50 m of wire Q due to the current in P.\n
\n\n [2]\n
\n\n From Newton’s third law, the force on a length of Q is equal but opposite to the force on the same length of P ✓\n
\n\n \n ✓\n
\n\n Calculate, in MeV, the energy released in this decay.\n
\n\n [2]\n
\n\n (\n \n m\n \n \n polonium\n \n −\n \n m\n \n \n lead\n \n −\n \n m\n \n α\n \n \n )\n \n c\n \n \n 2\n \n \n \n OR\n \n \n (209.93676 − 205.92945 − 4.00151)\n
\n\n \n \n OR\n \n \n
\n\n mass difference = 5.8 × 10\n \n −3\n \n ✓\n
\n\n
\n\n conversion to MeV using 931.5 to give 5.4 «MeV» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n .\n \n
\n\n \n Award\n \n [1]\n \n for 8.6 x 10\n \n −13\n \n J.\n \n
\n\n Generally, well answered. There were quite a few who fell into the trap of multiplying by an unnecessary c\n \n 2\n \n as they were not sure of the significance of the unit of u.\n
\n\n The polonium nucleus was stationary before the decay.\n
\n\n Show, by reference to the momentum of the particles, that the kinetic energy of the alpha particle is much greater than the kinetic energy of the lead nucleus.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n energy ratio expressed in terms of momentum, e.g.\n \n ✓\n
\n\n \n hence\n \n ✓\n
\n\n
\n\n \n «so\n \n has a much greater KE»\n
\n\n \n \n OR\n \n \n
\n\n \n «much» greater than\n \n «so\n \n has a much greater KE» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n alpha particle and lead particle have equal and opposite momenta ✓\n
\n\n so their velocities are inversely proportional to mass ✓\n
\n\n but KE ∝\n \n v\n \n \n 2\n \n «so\n \n has a much greater KE» ✓\n
\n\n Those who answered using the mass often did not get MP3 whereas those who converted to the number of particles or moles before the first calculation did, although that could be considered an unnecessary complication.\n
\n\n What are the changes in speed, frequency and wavelength of light as it travels from a material of low refractive index to a material of high refractive index?\n
\n\n \n
\n [1]\n
\n\n D\n
\n\n This question was well answered by the majority of candidates.\n
\n\n A radioactive nuclide X decays into a nuclide Y. The graph shows the variation with time of the activity\n \n A\n \n of X. X and Y have the same nucleon number.\n
\n\n \n
\n What is true about nuclide X?\n
\n\n A. alpha (α) emitter with a half-life of\n \n t\n \n
\n\n B. alpha (α) emitter with a half-life of 2\n \n t\n \n
\n\n C. beta-minus (β\n \n −\n \n ) emitter with a half-life of\n \n t\n \n
\n\n D. beta-minus (β\n \n −\n \n ) emitter with a half-life of 2\n \n t\n \n
\n\n [1]\n
\n\n D\n
\n\n \n Light of frequency 500 THz is incident on a single slit and forms a diffraction pattern. The first diffraction minimum forms at an angle of 2.4 x 10\n \n –3\n \n rad to the central maximum. The frequency of the light is now changed to 750 THz. What is the angle between the first diffraction minimum and the central maximum?\n \n
\n\n \n A. 1.6 × 10\n \n –3\n \n rad\n
\n \n
\n \n B. 1.8 × 10\n \n –3\n \n rad\n
\n \n
\n \n C. 2.4 × 10\n \n –3\n \n rad\n
\n \n
\n \n D. 3.6 × 10\n \n –3\n \n rad\n \n
\n\n [1]\n
\n\n A\n
\n\n State the nucleon number of the He isotope that\n \n decays into.\n
\n\n [1]\n
\n\n 3 ✓\n
\n\n
\n\n \n Do\n \n not\n \n accept\n \n by itself.\n \n
\n\n When heating a metal rod at one end, thermal energy is transferred along the rod.\n
\n\n \n
\n Which statement explains this transfer?\n
\n\n
\n A. Free electrons transfer kinetic energy to the ions in the metal\n
\n B. Intermolecular potential energy increases throughout the metal\n
\n\n C. Intermolecular potential energy is transferred to kinetic energy\n
\n\n D. Ions in the metal radiate energy in all directions\n
\n\n [1]\n
\n\n A\n
\n\n Alternative A is not necessarily the only possible explanation of the energy transfer, but it is certainly the best one of the four. Metals are usually good thermal conductors for the same reason that they are excellent electrical conductors - thanks to the presence of free electrons.\n
\n\n There are 85 turns of wire in the loop. Calculate the maximum induced emf in the loop.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n maximum flux at «\n \n »\n \n «Wb» ✓\n
\n\n emf = «\n \n »\n \n «V» ✓\n
\n\n \n \n
\n ALTERNATIVE 2\n \n \n
\n emf induced in one turn =\n \n BvL\n \n =\n \n «V» ✓\n
\n\n emf\n \n «V» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n \n Identify, on the HR diagram, the position of the Sun. Label the position S.\n \n
\n\n [1]\n
\n\n \n the letter S should be in the region of the shaded area\n \n \n \n ✔\n \n \n
\n\n \n \n \n
\n Locating the Sun’s position on the HR diagram was correctly done by most candidates, although a few were unsure of the surface temperature of the Sun.\n
\n\n A long straight vertical conductor carries a current\n \n I\n \n upwards. An electron moves with horizontal speed\n \n v\n \n to the right.\n
\n\n \n
\n What is the direction of the magnetic force on the electron?\n
\n\n A. Downwards\n
\n\n B. Upwards\n
\n\n C. Into the page\n
\n\n D. Out of the page\n
\n\n [1]\n
\n\n A\n
\n\n Calculate\n \n for a speed of 0.80\n \n c\n \n .\n
\n\n [1]\n
\n\n \n ✓\n
\n\n Which is correct for the tangential acceleration of a simple pendulum at small amplitudes?\n
\n\n A. It is inversely proportional to displacement.\n
\n\n B. It is proportional to displacement.\n
\n\n C. It is opposite to displacement.\n
\n\n D. It is proportional and opposite to displacement\n
\n\n [1]\n
\n\n D\n
\n\n \n Photons of discrete energy are emitted during gamma decay. This is evidence for\n
\n \n
\n \n A. atomic energy levels.\n
\n \n
\n \n B. nuclear energy levels.\n
\n \n
\n \n C. pair annihilation.\n
\n \n
\n \n D. quantum tunneling.\n \n
\n\n [1]\n
\n\n B\n
\n\n Outline why this force does no work on Phobos.\n
\n\n [1]\n
\n\n the force/field and the velocity/displacement are at 90° to each other\n \n \n OR\n \n \n
\n\n there is no change in GPE of the moon/Phobos ✔\n
\n\n Some candidates connected the idea that the gravitational force is perpendicular to the velocity (and hence the displacement) for the mark. It was also allowed to discuss that there is no change in gravitational potential energy, so therefore no work was being done. It was not acceptable to simply state that the net displacement over one full orbit is zero. Unfortunately, some candidates suggested that there is no net force on the moon so there is no work done, or that the moon is so much smaller so no work could be done on it.\n
\n\n The missing section of insulation is 0.56 m long and the external radius of the pipe is 0.067 m. The emissivity of the pipe surface is 0.40. Determine the energy lost every second from the pipe surface. Ignore any absorption of radiation by the pipe surface.\n
\n\n [3]\n
\n\n use of\n \n where\n \n T\n \n = 357 K ✓\n
\n\n use of\n \n « = 0.236 m\n \n 2\n \n » ✓\n
\n\n \n P\n \n = 87 «W» ✓\n
\n\n
\n\n \n Allow 85 – 89 W for\n \n MP3\n \n .\n \n
\n\n \n Allow ECF for\n \n MP3\n \n .\n \n
\n\n Candidates at both levels were able to recognize that this was a blackbody radiation question. One common mistake candidates made was not calculating the area of a cylinder properly. It is important to remind candidates that they are expected to know how to calculate areas and volumes for basic geometric shapes. Other common errors included the use of T in Celsius and neglecting to raise T ^4. Examiners awarded a large number of ECF marks for candidates who clearly showed work but made these fundamental errors.\n
\n\n Two wave generators, placed at position P and position Q, produce water waves with a wavelength of\n \n . Each generator, operating alone, will produce a wave oscillating with an amplitude of\n \n at position R. PR is\n \n and RQ is\n \n .\n
\n\n \n
\n Both wave generators now operate together in phase. What is the amplitude of the resulting wave at R?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D. zero\n
\n\n [1]\n
\n\n D\n
\n\n Draw, on the axes, a graph to show the variation with\n \n t\n \n of the displacement of particle Q.\n
\n\n [2]\n
\n\n oscillation in antiphase ✓\n
\n\n smaller amplitude than P ✓\n
\n\n
\n \n
\n Although there were good answers which scored full marks, there were a significant number of wrong answers where the amplitude was the same or not consistent throughout, or the wave drawn was not in antiphase of the original sketch.\n
\n\n State the de Broglie hypothesis.\n
\n\n [2]\n
\n\n a moving particle has wave properties ✓\n
\n\n de Broglie wavelength = Planck constant÷momentum (must define p if quoted as equation) ✓\n
\n\n \n In order to find the uncertainty for\n \n \n \n \n \n , a maximum gradient line would be drawn. On the graph, sketch the maximum gradient line for the data.\n \n
\n\n [1]\n
\n\n \n straight line, gradient\n \n g\n \n \n \n \n reater\n \n \n \n than line of best fit, and within the error bars\n \n \n ✓\n \n
\n\n \n \n \n
\n Almost all candidates were able to draw the correct maximum gradient line.\n
\n\n Boiling water is heated in a 2 kW electric kettle. The initial mass of water is 0.4 kg. Assume the specific latent heat of vaporization of water is 2 MJ kg\n \n –1\n \n .\n
\n\n What is the time taken for all the water to vaporize?\n
\n\n A. 250 s\n
\n\n B. 400 s\n
\n\n C. 2500 s\n
\n\n D. 4000 s\n
\n\n [1]\n
\n\n B\n
\n\n This question was well answered by candidates.\n
\n\n Discuss the ratios in (a) and (c).\n
\n\n [2]\n
\n\n the answers are the same ✓\n
\n\n count rates cannot vary from frame to frame /\n \n \n OWTTE\n \n \n ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from\n \n (c)\n \n .\n \n
\n\n \n \n Award [2]\n \n for “count rates cannot vary” if student made a mistake\n \n OR\n \n no answer in\n \n (c)\n \n and well discussed here.\n \n
\n\n Outline why electrons are never emitted for radiation C.\n
\n\n [1]\n
\n\n photon energy is less than both work functions\n
\n \n \n OR\n \n \n
\n photon energy is insufficient «to remove an electron»\n \n ✓\n \n
\n \n
\n Answer must be in terms of photon energy.\n \n
\n Calculate, for the cylinder, at the instant just before the block hits the ground the kinetic energy.\n
\n\n [2]\n
\n\n \n ω\n \n =<\n \n \n \n Δ\n \n t =\n \n \n \n \n \n Δt =\n \n \n \n \n \n \n = > 8.99 «rads\n \n −1\n \n » ✔\n
\n\n \n E\n \n \n k\n \n = «\n \n \n \n \n Iω\n \n \n 2\n \n \n =\n \n \n \n \n \n MR\n \n \n 2\n \n \n ω\n \n 2\n \n \n =\n \n \n \n \n \n × 12 × 0.20\n \n 2\n \n × 8.99\n \n 2\n \n = » 9.7 «J»\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n Angular speed, angular momentum and the kinetic energy of the cylinder at the instant given were successfully calculated by only the better-prepared candidates. Students were mostly able to recognize the correct expressions to use but struggled to find the angular speed in many instances. Error carried forward was very common throughout this question for students who incorrectly determined the angular velocity but understood and correctly applied the momentum and energy equations. In ii), quite a high number of candidates misread the question and calculated the energy of the whole system.\n
\n\n \n In the reference frame of the train a ball travels with speed 0.50\n \n c\n \n from the back to the front of the train, as the train passes the platform. Calculate the time taken for the ball to reach the front of the train in the reference frame of the train.\n \n
\n\n [1]\n
\n\n \n \n
\n \n
\n Because there were three frames of reference in this question many candidates struggled to find the simple value for the time of the ball’s travel down the train in the train’s frame of reference.\n
\n\n Determine the minimum area of the solar heating panel required to increase the temperature of all the water in the tank to 30°C during a time of 1.0 hour.\n
\n\n [3]\n
\n\n energy required = 250 × 4200 × (30 − 15) ✓\n
\n\n energy available = 0.30 × 680 ×\n \n t\n \n ×\n \n A\n \n ✓\n
\n\n \n A\n \n = «\n \n » 21 «m\n \n 2\n \n »\n \n \n OR\n \n \n 22 «m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Accept the correct use of 0.30 in either\n \n MP1\n \n or\n \n MP2\n \n .\n \n
\n\n Most candidates had a good attempt at this but there were often slight slips. Some missed the efficiency of the process. Some included the albedo of the roof tiles. Some thought that the temperature rise needed to have 273 added to convert to kelvin. However, sometimes scoring through ECF (error carried forward), the average mark was around 2 marks.\n
\n\n The highest and lowest temperatures of the gas during the cycle are 602 K and 92 K.\n
\n\n The efficiency of this engine is about 0.6. Outline how these data are consistent with the second law of thermodynamics.\n
\n\n [2]\n
\n\n \n e\n \n \n c\n \n = 1 −\n \n = 0.847 ✓\n
\n\n this engine has\n \n e\n \n <\n \n e\n \n \n c\n \n as it should ✓\n
\n\n
\n\n \n \n Award [0]\n \n if no calculation shown.\n \n
\n\n Explain why the received intensity varies between maximum and minimum values.\n
\n\n [3]\n
\n\n movement of B means that path distance is different « between BM and AM »\n
\n \n \n OR\n \n \n
\n movement of B creates a path difference «between BM and AM» ✓\n
\n interference\n
\n \n \n OR\n \n \n
\n superposition «of waves» ✓\n
\n maximum when waves arrive in phase / path difference = n x lambda\n
\n \n \n OR\n \n \n
\n minimum when waves arrive «180° or\n \n » out of phase / path difference = (n+½) x lambda ✓\n
\n This was an \"explain\" questions, so examiners were looking for a clear discussion of the movement of speaker B creating a changing path difference between B and the microphone and A and the microphone. This path difference would lead to interference, and the examiners were looking for a connection between specific phase differences or path differences for maxima or minima. Some candidates were able to discuss basic concepts of interference (e.g. \"there is constructive and destructive interference\"), but failed to make clear connections between the physical situation and the given graph. A very common mistake candidates made was to think the question was about intensity and to therefore describe the decrease in peak height of the maxima on the graph. Another common mistake was to approach this as a Doppler question and to attempt to answer it based on the frequency difference of B.\n
\n\n An astronaut is orbiting Earth in a spaceship. Why does the astronaut experience weightlessness?\n
\n\n A. The astronaut is outside the gravitational field of Earth.\n
\n\n B. The acceleration of the astronaut is the same as the acceleration of the spaceship.\n
\n\n C. The spaceship is travelling at a high speed tangentially to the orbit.\n
\n\n D. The gravitational field is zero at that point.\n
\n\n [1]\n
\n\n B\n
\n\n State the units of\n \n A\n \n .\n
\n\n [1]\n
\n\n kV s ✓\n
\n\n Show that during an adiabatic expansion of an ideal monatomic gas the temperature\n \n \n \n \n \n and volume\n \n \n \n \n \n are given by\n
\n\n \n \n \n \n \n = constant\n
\n\n [2]\n
\n\n substitution of\n \n \n \n \n in\n \n \n \n \n ✔\n
\n\n manipulation to get result ✔\n
\n\n The algebraic manipulation required for this question was well mastered by only the better-prepared candidates. Many candidates tried to find the required formula via randomly selected equations from the data booklet.\n
\n\n Sketch, on the axes, a graph to show the variation with time of the magnetic flux linkage\n \n in the loop.\n
\n\n \n
\n [1]\n
\n\n \n
\n shape as above ✓\n
\n\n Describe\n \n two\n \n ways in which standing waves differ from travelling waves.\n
\n\n [2]\n
\n\n energy is not propagated by standing waves\n \n ✓\n \n
\n\n amplitude constant for travelling waves\n \n \n OR\n \n \n amplitude varies with position for standing waves\n \n \n OR\n \n \n standing waves have nodes/antinodes\n \n ✓\n \n
\n\n phase varies with position for travelling waves\n \n \n OR\n \n \n phase constant inter-node for standing waves\n \n ✓\n \n
\n\n travelling waves can have any wavelength\n \n \n OR\n \n \n standing waves have discrete wavelengths\n \n ✓\n \n
\n\n \n \n
\n OWTTE\n \n \n
\n An insulated tube is filled with a large number\n \n n\n \n of lead spheres, each of mass\n \n m\n \n . The tube is inverted\n \n s\n \n times so that the spheres completely fall through an average distance\n \n L\n \n each time. The temperature of the spheres is measured before and after the inversions and the resultant change in temperature is\n \n ΔT\n \n .\n
\n\n What is the specific heat capacity of lead?\n
\n\n \n
\n
\n\n A.\n \n \n \n \n \n
\n\n \n B.\n \n \n \n \n \n \n
\n\n \n \n C.\n \n \n \n \n \n
\n\n \n \n D.\n \n \n \n \n \n
\n\n
\n\n [1]\n
\n\n B\n
\n\n \n Show that the value of\n \n \n \n \n \n is about 0.03.\n \n
\n\n [2]\n
\n\n \n gradient\n \n «\n \n »\n \n
\n \n \n \n \n OR\n \n \n
\n \n \n use of equation with coordinates of a point\n \n \n ✓\n \n
\n \n
\n \n \n \n ✓\n \n
\n
\n\n \n \n MP1 allow gradients in range\n \n to\n \n
\n \n \n
\n \n \n MP2 allow a range\n \n to\n \n for\n \n \n \n \n \n
\n\n
\n\n Very well answered either by obtaining the gradient or replacing with the coordinates of a point.\n
\n\n Estimate, using the graph, the maximum height of the bottle.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Attempt to count squares ✓\n
\n\n Area of one square found ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4 m) ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n Uses area equation for either triangle ✓\n
\n\n Correct read offs for estimate of area of triangle ✓\n
\n\n 7.2 «m» (accept 6.4 – 7.4) ✓\n
\n\n Two forces, F and G, act on a system.\n
\n\n \n
\n F is reversed in direction and G is halved.\n
\n\n Which vector correctly represents the new resultant force?\n
\n
\n
\n \n
\n [1]\n
\n\n D\n
\n\n A single loop of wire of resistance 10 Ω has its plane perpendicular to a changing magnetic field.\n
\n\n The graph shows the variation with time of the magnetic flux linked through the loop of wire.\n
\n\n \n
\n What is the maximum current in the loop of wire?\n
\n\n
\n A. 1.0 A\n
\n B. 2.0 A\n
\n\n C. 4.0 A\n
\n\n D. 20 A\n
\n\n [1]\n
\n\n B\n
\n\n A student models the relationship between the pressure\n \n p\n \n of a gas and its temperature\n \n T\n \n as\n \n p\n \n =\n \n \n \n +\n \n \n \n T.\n
\n\n The units of\n \n p\n \n are pascal and the units of\n \n T\n \n are kelvin. What are the fundamental SI units of\n \n \n \n \n \n and\n \n \n \n \n \n ?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Calculate the energy released when one mole of strontium-90 decays to 2% of its original activity forming the stable daughter product.\n
\n\n [3]\n
\n\n Idea that the Yttrium half life is much less than Strontium so can assume all Yttrium energy is included. ✓\n
\n\n \n seen ✓\n
\n\n \n
\n\n Answer\n \n GJ ✓\n
\n\n Draw on the axes the variation of gravitational potential between O and M.\n
\n\n [1]\n
\n\n Line always negative, of suitable shape and end point below −8 and above −20 unless awarding\n \n \n ECF\n \n \n from\n \n \n b(iv)\n \n \n ✓\n
\n\n \n
\n State the de Broglie hypothesis.\n
\n\n [2]\n
\n\n a moving particle has wave properties ✓\n
\n\n de Broglie wavelength = Planck constant÷momentum (must define p if quoted as equation) ✓\n
\n\n Suggest what happens to the vertical component of momentum of the cannon when the shell is fired.\n
\n\n [1]\n
\n\n Must be transferred into the ground beneath the cannon\n \n OR\n \n into the suspension system ✓\n
\n\n Explain why the output potential difference to the external circuit and the output emf of the photovoltaic cell are different.\n
\n\n
\n\n [2]\n
\n\n there is a potential difference across the internal resistance\n
\n \n \n OR\n \n \n
\n there is energy/power dissipated in the internal resistance\n \n ✓\n \n
\n when there is current «in the cell»/as charge flows «through the cell»\n \n ✓\n \n
\n\n \n
\n Allow full credit for answer based on\n \n \n
\n The temperature of the air outside of the bottle is 20 °C. The surface area of the bottle is 4.0 × 10\n \n −2\n \n m\n \n 2\n \n . Calculate the initial rate of thermal energy transfer by conduction through the bottle.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n 480 «W» ✓\n
\n\n Show that\n \n .\n
\n\n [1]\n
\n\n The vertical momentum is zero hence\n \n ✓\n
\n\n «leading to the expected result» ✓\n
\n\n \n Show that the number of helium atoms in the container is about 4 × 10\n \n 20\n \n .\n \n
\n\n [2]\n
\n\n \n \n \n \n \n
\n\n \n \n OR\n \n \n
\n\n \n \n \n \n \n ✔\n \n \n
\n\n \n \n N\n \n = 3.7\n \n ×\n \n 10\n \n 20\n \n ✔\n \n
\n\n Again at HL this was very well answered with the most common approach being to calculate the number of moles and then multiply by N\n \n A\n \n to calculate the number of atoms. At SL many candidates calculated n but stopped there. Also at SL there was some evidence of candidates working backwards and magically producing a value for ‘n’ that gave a result very close to that required after multiplying by N\n \n A\n \n .\n
\n\n Energy is transferred to water in a flask at a rate\n \n P\n \n . The water reaches boiling point and then\n \n P\n \n is increased. What are the changes to the temperature of the water and to the rate of vaporization of the water after the change?\n
\n\n \n
\n
\n\n [1]\n
\n\n D\n
\n\n A projectile is launched with a velocity\n \n at an angle\n \n to the horizontal. It reaches a maximum height\n \n . What is the time taken to reach the maximum height?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n This question is very easily answered by elimination. The time to reach max height is the same as for a projectile launched vertically with initial speed\n \n , and no other alternative than D contains the term\n \n .\n
\n\n Discuss, for this process, the changes that occur in the internal energy of the gas.\n
\n\n [2]\n
\n\n internal energy is constant ✓\n
\n\n
\n internal energy depends on kinetic energy/temperature «only»\n
\n \n \n OR\n \n \n
\n\n since temperature/kinetic energy is constant ✓\n
\n\n
\n\n \n Do not award\n \n MP2\n \n for stating that “temperature is constant” unless linked to the correct conclusion, as that is mentioned in the stem.\n \n
\n\n \n Award\n \n MP2\n \n for stating that kinetic energy remains constant.\n \n
\n\n \n explain why the entropy of the gas decreases.\n \n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n «from b(i)»\n \n is negative\n \n ✔\n \n \n
\n\n \n \n \n \n AND\n \n \n \n is negative\n \n ✔\n \n \n
\n\n
\n\n \n ALTERNATIVE 2\n \n
\n\n \n T\n \n and/or\n \n V\n \n decreases ✔\n
\n\n less disorder/more order «so\n \n S\n \n decreases» ✔\n
\n\n
\n\n \n ALTERNATIVE 3\n \n
\n\n \n T\n \n decreases ✔\n
\n\n \n ✔\n
\n\n \n \n
\n\n \n NOTE: Answer given, look for a valid reason that S decreases.\n \n
\n\n Sketch, on the axes, a graph to show the variation with time of the magnetic flux linkage\n \n in the loop.\n
\n\n \n
\n [1]\n
\n\n \n
\n shape as above ✓\n
\n\n An object is pushed from rest by a constant net force of 100 N. When the object has travelled 2.0 m the object has reached a velocity of 10 m s\n \n −1\n \n .\n
\n\n What is the mass of the object?\n
\n\n A. 2 kg\n
\n\n B. 4 kg\n
\n\n C. 40 kg\n
\n\n D. 200 kg\n
\n\n [1]\n
\n\n B\n
\n\n The orbital radius of Titan around Saturn is\n \n and the period of revolution is\n \n .\n
\n\n Show that\n \n where\n \n is the mass of Saturn.\n
\n\n [2]\n
\n\n correct equating of gravitational force / acceleration to centripetal force / acceleration ✓\n
\n\n correct rearrangement to reach the expression given ✓\n
\n\n
\n\n \n Allow use of\n \n for\n \n MP1\n \n .\n \n
\n\n A pure sample of iodine-131 decays into xenon with a half-life of 8 days.\n
\n\n What is\n \n after 24 days?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n The majority of candidates correctly selected option B. This question had the highest discrimination index on the HL paper.\n
\n\n Explain why there is no effect on the table of results when the intensity of source B is doubled.\n
\n\n [1]\n
\n\n changing/doubling intensity «changes/doubles number of photons arriving but» does not change energy of photon\n \n ✓\n \n
\n\n \n The orbital radius of the Earth around the Sun is 1.5 times that of Venus. What is the intensity of solar radiation at the orbital radius of Venus?\n
\n \n
\n \n A. 0.6 kW m\n \n -2\n \n
\n \n
\n \n B. 0.9 kW m\n \n -2\n \n
\n \n
\n \n C. 2 kW m\n \n -2\n \n
\n \n
\n \n D. 3 kW m\n \n -2\n \n \n
\n\n [1]\n
\n\n D\n
\n\n This had a low discrimination index at both SL and HL and although the correct answer was the most popular, all options gained high support. Candidates should be reminded that they have a data booklet and become familiar with its contents before the exam.\n
\n\n Calculate the ratio\n \n \n \n \n \n where\n \n V\n \n C\n \n \n is the volume of the gas at C and\n \n V\n \n B\n \n \n is the volume at B.\n
\n\n [2]\n
\n\n \n \n \n \n \n ✔\n
\n\n \n \n \n \n \n ✔\n
\n\n \n Award\n \n [2]\n \n for bald correct answer.\n \n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n A transverse water wave travels to the right. The diagram shows the shape of the surface of the water at time\n \n t\n \n = 0. P and Q show two corks floating on the surface.\n
\n\n \n
\n
\n\n «A wave where the» displacement of particles/oscillations of particles/movement of particles/vibrations of particles is perpendicular/normal to the direction of energy transfer/wave travel/wave velocity/wave movement/wave propagation ✓\n
\n\n
\n\n \n Allow medium, material, water, molecules, or atoms for particles.\n \n
\n\n Explain the pattern seen on the screen.\n
\n\n [3]\n
\n\n Mention of interference / superposition ✓\n
\n\n Bright fringe occurs when light from the slits arrives in phase ✓\n
\n\n Dark fringe occurs when light from the slits arrives 180°/\n \n out of phase ✓\n
\n\n \n Explain why the kinetic energy of the proton is constant.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n
\n work done by force is change in kinetic energy ✔\n
\n work done is zero/force perpendicular to velocity ✔\n
\n \n
\n \n \n NOTE: Award\n \n [2]\n \n for a reference to work done is zero hence E\n \n k\n \n remains constant\n \n
\n \n
\n
\n\n \n \n \n ALTERNATIVE 2\n \n \n
\n proton moves at constant speed ✔\n
\n kinetic energy depends on speed ✔\n
\n \n
\n \n \n NOTE: Accept mention of speed or velocity indistinctly in MP2\n \n
\n \n
\n
\n\n Outline why it is unlikely that the relationship between\n \n T\n \n and\n \n V\n \n is linear.\n
\n\n [1]\n
\n\n it is not possible to draw a straight line through all the error bars ✓\n
\n\n A photon has a wavelength\n \n . What are the energy and momentum of the photon?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Explain the variation in intensity.\n
\n\n [3]\n
\n\n «incident and reflected» waves superpose/interfere/combine ✓\n
\n\n «that leads to» standing waves formed\n \n \n OR\n \n \n nodes and antinodes present ✓\n
\n\n at antinodes / maxima there is maximum intensity / constructive interference / «displacement» addition / louder sound ✓\n
\n\n at nodes / minima there is minimum intensity / destructive interference / «displacement» cancellation / quieter sound ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n \n Allow a sketch of a standing wave for\n \n MP2\n \n \n
\n\n \n Allow a correct reference to path or phase differences to identify constructive / destructive interference\n \n
\n\n ai) On most occasions it looked like students knew more than they could successfully communicate. Lots of answers talked about interference between the 2 waves, or standing waves being produced but did not go on to add detail. Candidates should take note of how many marks the question part is worth and attempt a structure of the answer that accounts for that. At SL there were problems recognizing a standard question requiring the typical explanation of how a standing wave is established.\n
\n\n 3aii) By far the most common answer was 2800 Hz, not doubling the value given to get the correct wavelength. That might suggest that some students misinterpreted adjacent minima as two troughs, therefore missing to use the information to correctly determine the wavelength as 0.24 m.\n
\n\n b) A question that turned out to be a good high level discriminator. Most candidates went for an answer that generally had everything at a lower intensity and didn't pick up on the relative amount of superposition. Those that did answer it very well, with very clear explanations, succeeded in recognizing that the nodes would be louder and the anti-nodes would be quieter than before.\n
\n\n When the spheres move outward, the angular speed decreases from 20 rad s\n \n −1\n \n to 12 rad s\n \n −1\n \n . Calculate the percentage change in rotational kinetic energy that occurs when the spheres move outward.\n
\n\n [2]\n
\n\n \n «E\n \n \n k\n \n =»\n \n \n Lω\n \n \n 1\n \n \n =\n \n Lω\n \n 2\n \n \n ✓\n
\n\n \n \n OR\n \n \n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n «\n \n L\n \n is constant so»\n \n E\n \n \n k\n \n is proportional to\n \n ω\n \n ✓\n
\n\n 40 % «energy loss» ✓\n
\n\n
\n\n \n \n MP1\n \n is for understanding that angular momentum is constant so change in rotational kinetic energy is proportional to change in angular velocity\n \n
\n\n \n \n Award [0]\n \n if E = 0.5 I ω\n \n 2\n \n is used with the same I value for both values of E\n \n
\n\n \n Award\n \n [2]\n \n for\n \n BCA\n \n \n
\n\n Show that the speed of the load when it hits the floor is about 2.1 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n proper use of kinematic equation ✓\n
\n\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Must see either the substituted values\n \n OR\n \n a value for v to at least three s.f. for\n \n MP2\n \n .\n \n
\n\n This was a \"show that\" questions, so examiners were looking for a clear equation leading to a clear substitution of values leading to an answer that had more significant digits than the given answer. Most candidates successfully selected the correct equation and showed a proper substitution. Some candidates started with an energy approach that needed modification as it clearly led to an incorrect solution. These responses did not receive full marks.\n
\n\n Calculate the maximum current in the chamber due to the electrons when there is no smoke in the chamber.\n
\n\n [3]\n
\n\n Each alpha gives rise to\n \n ion pairs ✓\n
\n\n So\n \n ion pairs per second ✓\n
\n\n current\n \n «A» ✓\n
\n\n \n Estimate, using the graph, the radius of a carbon-12 nucleus.\n \n
\n\n [2]\n
\n\n \n «\n \n \n \n »\n \n \n \n \n \n «m»\n \n \n ✔\n
\n \n
\n \n \n \n \n «m» ✔\n \n
\n\n Many candidates answered this well but calculated the diameter rather than the radius.\n
\n\n Two copper wires of equal lengths but different diameters are used to connect a cell to a load. Wire 1 has a diameter\n \n M\n \n , wire 2 has a diameter 2\n \n M\n \n . The electron drift velocities in wires 1 and 2 are\n \n and\n \n .\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n A moderately difficult question, with incorrect alternative A selected by a significant fraction of the candidates. Alternative A represents the reciprocal of the correct answer, suggesting an algebraic problem with manipulating fractions. The question implies equal current in both wires and equal carrier density. From drift speed equation, a 4× greater cross-sectional area of wire 2 results in a 4× smaller drift speed of charge carriers.\n
\n\n \n Suppose the star could contract to half its original radius without any loss of mass. Discuss the effect, if any, this has on the total energy of the planet.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n
\n \n
\n \n «at the position of the planet» the potential depends only on the mass of the star /does not depend on the radius of the star ✔\n
\n \n
\n \n the potential will not change and so the energy will not change ✔\n
\n \n
\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n
\n \n r / distance between the centres of the objects / orbital radius remains unchanged ✔\n
\n \n
\n \n since\n \n \n \n , energy will not change\n \n ✔\n \n \n
\n\n
\n\n A large number of candidates thought that the total energy of the planet would change, mostly double.\n
\n\n draw a free-body diagram for the ball.\n
\n\n \n
\n [2]\n
\n\n Tension upwards, weight downwards ✓\n
\n Tension is clearly longer than weight ✓\n
\n
\n\n \n Look for:\n \n
\n\n \n
\n Suggest why AC is the adiabatic part of the cycle.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «considering expansions from A» an adiabatic process will reduce/change temperature ✓\n
\n\n and so curve AC must be the steeper ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n temperature drop occurs for BC ✓\n
\n\n therefore CA must increase temperature «via adiabatic process». ✓\n
\n\n The energy released in the reaction is about 180 MeV. Estimate, in J, the energy released when 1 kg of\n \n undergoes fission.\n
\n\n [3]\n
\n\n Mass of uranium nucleus\n \n ✓\n
\n\n \n ✓\n
\n\n \n «J» ✓\n
\n\n \n The frequency of the oscillator is reduced to 120 Hz. On the diagram, draw the standing wave that will be formed on the string.\n \n
\n\n \n
\n [1]\n
\n\n \n first harmonic mode drawn ✔\n \n
\n\n \n \n \n
\n \n \n NOTE: Allow if only one curve drawn, either solid or dashed.\n \n \n
\n\n Mass\n \n is attached to one end of a string. The string is passed through a hollow tube and mass\n \n is attached to the other end. Friction between the tube and string is negligible.\n
\n\n \n
\n Mass\n \n travels at constant speed\n \n in a horizontal circle of radius\n \n . What is mass\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n The tube is raised until the loudness of the sound reaches a maximum for a\n \n second time\n \n .\n
\n\n Draw, on the following diagram, the position of the nodes in the tube when the second maximum is heard.\n
\n\n \n
\n [1]\n
\n\n nodes shown at water surface\n \n \n AND\n \n \n \n way up tube (by eye)\n \n ✓\n \n
\n\n \n
\n Accept drawing of displacement diagram for correct harmonic without nodes specifically identified.\n \n
\n \n Award\n \n [0]\n \n if waveform is shown below the water surface\n \n
\n\n \n Calculate, in Hz, the frequency for this wave.\n \n
\n\n [2]\n
\n\n \n \n λ\n \n = 0.30 «m» ✔\n
\n \n = «\n \n » 830 «Hz» ✔\n \n
\n \n NOTE:\n \n \n \n Allow ECF from (a)(i)\n
\n Allow ECF from wrong wavelength for MP2\n \n \n
\n \n Monochromatic light travelling upwards in glass is incident on a boundary with air. The path of the refracted light is shown.\n \n
\n\n \n \n \n
\n \n \n A layer of liquid is then placed on the glass without changing the angle of incidence on the glass. The refractive index of the glass is greater than the refractive index of the liquid and the refractive index of the liquid is greater than that of air.\n \n \n
\n\n \n \n What is the path of the refracted light when the liquid is placed on the glass?\n \n \n
\n\n \n \n \n \n \n
\n [1]\n
\n\n D\n
\n\n A low discrimination index with most candidates choosing C. They have deduced, correctly, that the ray moves away from the normal on entering the denser medium but have apparently forgotten that the stem of the question has shown them that it reaches the glass-air boundary at an angle greater than the critical angle.\n
\n\n \n two\n \n difficulties of energy production by nuclear fusion.\n
\n\n [2]\n
\n\n Requires high temp/pressure ✓\n
\n Must overcome Coulomb/intermolecular repulsion ✓\n
\n Difficult to contain / control «at high temp/pressure» ✓\n
\n Difficult to produce excess energy/often energy input greater than output /\n \n \n OWTTE\n \n \n ✓\n
\n Difficult to capture energy from fusion reactions ✓\n
\n Difficult to maintain/sustain a constant reaction rate ✓\n
\n The side of the rod can be unlagged or ideally lagged. Explain the difference in energy transfer for these two cases.\n
\n\n [3]\n
\n\n When ideally lagged, no energy transfer can occur through the sides of the bar. ✓\n
\n\n All the power input/ energy input per second at one end will emerge at the other end. ✓\n
\n\n When unlagged, energy transfer occurs from the sides of the bar and the power /energy input per second at input > the energy output per second at the other end. ✓\n
\n\n
\n\n \n Max 1 if answer does not refer to rate of energy transfer in MP2 and MP3.\n \n
\n\n The speed of the tram is measured by detecting a beam of microwaves of wavelength 2.8 cm reflected from the rear of the tram as it moves away from the station. Predict the change in wavelength of the microwaves at the stationary microwave detector in the station.\n
\n\n [2]\n
\n\n Use of\n \n ✓\n
\n\n 1.2 nm ✓\n
\n\n A student quotes three equations related to atomic and nuclear physics:\n
\n\n I.\n \n
\n\n II.\n \n
\n\n III.\n \n
\n\n Which equations refer to the Bohr model for hydrogen?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n The flywheel was rotating at 150 rev per minute before the application of the angular impulse. Determine the change in angular rotational energy of the flywheel during the application of the flywheel.\n
\n\n [3]\n
\n\n Correct conversions to a consistent set of\n \n units ✓\n
\n\n \n or correct substitution seen ✓\n
\n\n 113 kJ ✓\n
\n\n Light of intensity 500 W m\n \n −2\n \n is incident on concrete and on snow. 300 W m\n \n −2\n \n is reflected from the\n
\n concrete and 400 W m\n \n −2\n \n is reflected from the snow.\n
\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D. 2\n
\n\n [1]\n
\n\n B\n
\n\n Outline how this standing wave pattern of melted spots is formed.\n
\n\n [2]\n
\n\n standing waves form «in the oven» by superposition / constructive interference ✓\n
\n\n energy transfer is greatest at the antinodes «of the standing wave pattern» ✓\n
\n\n \n Estimate, in Bq, the initial activity of the sample.\n \n
\n\n [2]\n
\n\n \n number of nuclei is\n \n \n \n ✔\n
\n \n
\n \n \n \n \n \n «\n \n \n \n »\n \n \n \n \n \n \n «Bq» ✔\n \n
\n\n Many scored the first mark for calculating the number of nuclei but neglected to convert λ to s\n \n -1\n \n .\n
\n\n Outline why work must be done on ring B as it moves towards ring A at a constant speed.\n
\n\n [2]\n
\n\n the current induced in B gives rise to a magnetic field opposing that of A\n
\n\n \n OR\n \n
\n\n there will be a magnetic force opposing the motion ✓\n
\n\n work must be done to move B in the opposite direction to this force ✓\n
\n\n \n X is a radioactive nuclide that decays to a stable nuclide. The activity of X falls to\n \n th of its original value in 32 s.\n
\n What is the half-life of X?\n \n
\n \n A. 2 s\n
\n \n
\n \n B. 4 s\n
\n \n
\n \n C. 8 s\n
\n \n
\n \n D. 16 s\n \n
\n\n [1]\n
\n\n C\n
\n\n Calculate, in nm,\n \n .\n
\n\n [3]\n
\n\n \n s\n \n =\n \n \n \n OR\n \n \n = 0.0188 «m» ✓\n
\n\n use of\n \n ✓\n
\n\n 450 «nm» ✓\n
\n\n \n Two forces act along a straight line on an object that is initially at rest. One force is constant; the second force is in the opposite direction and proportional to the velocity of the object.\n \n
\n\n \n \n \n
\n \n \n What is correct about the motion of the object?\n
\n \n \n
\n
\n\n \n \n A. The acceleration increases from zero to a maximum.\n
\n \n \n
\n \n \n B. The acceleration increases from zero to a maximum and then decreases.\n
\n \n \n
\n \n \n C. The velocity increases from zero to a maximum.\n
\n \n \n
\n \n \n D. The velocity increases from zero to a maximum and then decreases.\n \n \n
\n\n [1]\n
\n\n C\n
\n\n The frequency of the wave is 0.50 Hz. Calculate the speed of the wave.\n
\n\n [1]\n
\n\n \n v\n \n = «0.50 × 16 =» 8.0 «m s\n \n −1\n \n » ✓\n
\n\n \n Calculate the speed of the ball as it leaves the racket.\n \n
\n\n [2]\n
\n\n \n links 0.84 to Δ\n \n p\n \n ✔\n \n
\n\n \n \n «\n \n » 14.5 «m s\n \n –1\n \n »✔\n
\n \n
\n \n \n NOTE: Award\n \n [2]\n \n for bald correct answer\n \n \n
\n\n A body of height 40 cm and uniform cross-sectional area floats in water. 10 cm of the height of the body remains above the water line.\n
\n\n \n
\n The density of water is\n \n . What is the density of the body?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n D\n
\n\n Label, on the diagram with the letter P, the point on the\n \n ct\n \n ′ axis whose\n \n ct\n \n ′ coordinate is 1.00 ly.\n
\n\n [2]\n
\n\n identifies point with coordinates\n \n = 0,\n \n ct\n \n = 0.60 on vertical axis ✓\n
\n\n draws line parallel to the\n \n prime axis until it intersects the prime\n \n ct\n \n axis ✓\n
\n\n \n
\n
\n\n \n \n Award [2]\n \n for correct position of P without working shown.\n \n
\n\n Describe the changes in gravitational potential energy of the oscillating system from\n \n t\n \n = 0 as it oscillates through one cycle of its motion.\n
\n\n [1]\n
\n\n maximum GPE at extremes, minimum in centre ✔\n
\n\n This straightforward question had surprisingly poorly answers. Candidate answers tended to be overly vague, such as “as the bob went higher the GPE increased and as it fell the GPE decreased.” Candidates needed to specify when GPE would be at maximum and minimum values. Some candidates mistakenly assumed that at t=0 the pendulum bob was at maximum height despite being told otherwise in the question stem.\n
\n\n Two conductors\n \n S\n \n and\n \n T\n \n have the\n \n V\n \n /\n \n I\n \n characteristic graphs shown below.\n
\n\n \n
\n When the conductors are placed in the circuit below, the reading of the ammeter is 6.0 A.\n
\n\n \n
\n What is the emf of the cell?\n
\n\n A. 4.0 V\n
\n\n B. 5.0 V\n
\n\n C. 8.0 V\n
\n\n D. 13 V\n
\n\n [1]\n
\n\n A\n
\n\n The radius of the pulley is 2.5 cm. Calculate the angular speed of rotation of the pulley as the load hits the floor. State your answer to an appropriate number of significant figures.\n
\n\n [2]\n
\n\n use of\n \n to give 84 «rad s\n \n −1\n \n »\n
\n\n \n \n OR\n \n \n
\n\n \n to give 84 «rad s\n \n −1\n \n » ✓\n
\n\n
\n\n quoted to 2sf only✓\n
\n\n
\n\n This SL only question was generally well done. Despite some power of 10 errors, many candidates correctly reported final answer to 2 sf.\n
\n\n Calculate the thermal energy transferred from the sample during the first\n \n minutes.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n
\n\n \n Calculate the time for\n \n one\n \n complete revolution.\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n \n \n « s » ✔\n \n
\n\n \n \n NOTE: Award\n \n [2]\n \n for bald correct answer\n \n \n
\n\n During the nuclear fission of nucleus X into nucleus Y and nucleus Z, energy is released. The binding energies per nucleon of X, Y and Z are\n \n ,\n \n and\n \n respectively. What is true about the binding energy per nucleon of X, Y and Z?\n
\n\n
\n A.\n \n >\n \n and\n \n >\n \n
\n B.\n \n =\n \n and\n \n =\n \n
\n\n C.\n \n >\n \n and\n \n >\n \n
\n\n D.\n \n =\n \n +\n \n
\n\n [1]\n
\n\n A\n
\n\n Show that the magnitude of the resultant electric field at P is 3 MN C\n \n −1\n \n
\n\n [2]\n
\n\n «electric field at P from one charge is\n \n »\n \n
\n\n \n \n OR\n \n \n
\n\n \n «NC\n \n −1\n \n » ✓\n
\n\n
\n « net field is »\n \n «NC\n \n −1\n \n » ✓\n
\n \n Show that the work done on the gas for the isothermal process C→A is approximately 440 J.\n \n
\n\n [2]\n
\n\n \n evidence of work done equals area between AC and the Volume axis ✓\n
\n \n
\n \n reasonable method to estimate area giving a value 425 to 450 J ✓\n \n
\n\n \n \n \n Answer 440 J is given, check for valid working.\n
\n \n \n \n
\n \n \n \n Examples of acceptable methods for MP2:\n
\n \n \n \n
\n \n \n \n - estimates 17 to18 small squares x 25 J per square = 425 to 450 J.\n
\n - 250 J for area below BC plus a triangle of dimensions 5 × 3, 3 × 5, or 4 × 4 small square edges giving 250 J + 187.5 J or 250 J + 200 J.\n
\n \n \n \n
\n \n \n \n Accurate integration value is 438 J - if method seen award\n \n [2]\n \n .\n \n \n \n
\n\n At SL, Correct answers were rare and very few candidates used the fact the work done was area under the curve, and even fewer could estimate this area. At HL, the question was better answered. Candidates used a range of methods to estimate the area including counting the squares, approximating the area using geometrical shapes and on a few occasions using integral calculus.\n
\n\n \n Suggest, by reference to the graph, why it is unlikely that the relationship between\n \n T\n \n and\n \n v\n \n is linear.\n \n
\n\n [1]\n
\n\n \n a straight line cannot be drawn through all error bars\n
\n \n \n OR\n \n \n
\n the graph/line of best fit is /curved/not straight/parabolic etc.\n
\n \n \n OR\n \n \n
\n graph has increasing/variable gradient ✔\n \n
\n \n \n NOTE: Do not allow “a line cannot be drawn through all error bars” without specifying “straight”.\n \n \n
\n\n What is the relation between the value of the unified atomic mass unit in grams and the value of Avogadro’s constant in mol\n \n −1\n \n ?\n
\n\n A. Their ratio is 1.\n
\n\n B. Their product is 1.\n
\n\n C. Their sum is 1.\n
\n\n D. Their difference is 0.\n
\n\n [1]\n
\n\n B\n
\n\n Outline, by reference to nuclear binding energy, why the mass of a nucleus is less than the sum of the masses of its constituent nucleons.\n
\n\n [2]\n
\n\n according to Δ\n \n E\n \n = Δ\n \n mc\n \n \n 2\n \n / identifies mass energy equivalence ✓\n
\n\n
\n\n energy is released when nucleons come together / a nucleus is formed «so nucleus has less mass than individual nucleons»\n
\n\n \n \n OR\n \n \n
\n\n energy is required to «completely» separate the nucleons / break apart a nucleus «so individual nucleons have more mass than nucleus» ✓\n
\n\n
\n\n \n Accept protons and neutrons.\n \n
\n\n Still several answers that thought that the nucleus needed to gain energy to bind it together. Most candidates scored at least one for recognising some form of mass/energy equivalence, although few candidates managed to consistently express their ideas here.\n
\n\n Explain, by reference to Faraday’s law of electromagnetic induction, why there is an electromotive force (emf) induced in the loop as it leaves the region of magnetic field.\n
\n\n [2]\n
\n\n The induced emf is equal/proportional/related to the «rate of» change of «magnetic» flux/flux linkage ✓\n
\n\n Flux is changing because the area pierced/enclosed by magnetic field lines changes «decreases»\n
\n\n \n \n OR\n \n \n
\n\n Flux is changing because the loop is leaving/moving out of the «magnetic» field. ✓\n
\n\n \n Need to see a connection between the EMF and change in flux for\n \n MP1\n \n .\n \n
\n\n \n Need to see a connection between the area changing or leaving the field and the change in flux for\n \n MP2\n \n \n
\n\n Estimate the escape speed of the spacecraft from the planet–star system.\n
\n\n [2]\n
\n\n use of\n \n v\n \n \n esc\n \n =\n \n \n ✓\n \n
\n\n \n v =\n \n 9.91 × 10\n \n 4\n \n «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n
\n\n
\n\n Two charged parallel plates have electric potentials of 10 V and 20 V.\n
\n\n \n
\n A particle with charge +2.0 μC is moved from the 10 V plate to the 20 V plate. What is the change in the electric potential energy of the particle?\n
\n\n
\n A. −20 μJ\n
\n B. −10 μJ\n
\n\n C. 10 μJ\n
\n\n D. 20 μJ\n
\n\n [1]\n
\n\n D\n
\n\n The measurements of\n \n were collected five times. Explain how repeated measurements of\n \n reduced the random error in the final experimental value of\n \n .\n
\n\n [2]\n
\n\n \n mention of mean/average value «of\n \n \n \n \n \n »\n \n \n ✓\n \n
\n\n \n this reduces uncertainty in\n \n \n \n \n \n / result\n
\n \n \n \n \n OR\n \n \n
\n \n \n more accurate/precise\n \n \n ✓\n \n
\n
\n\n \n \n Reference to “random errors average out” scores MP1\n \n \n
\n\n \n \n Accept “closer to true value”, “more reliable value” OWTTE for MP2\n \n \n
\n\n
\n\n Most candidates stated that the mean of 5 values of\n \n T\n \n was used to obtain an answer closer to the true value if there were no systematic errors. Some just repeated the question.\n
\n\n An engineer needs to move a space probe of mass 3600 kg from Ganymede to Callisto. Calculate the energy required to move the probe from the orbital radius of Ganymede to the orbital radius of Callisto. Ignore the mass of the moons in your calculation.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n « multiplies by 3600 kg to get » 1.9 × 10\n \n 11\n \n «J»\n \n ✓\n \n
\n\n \n
\n Award\n \n [2]\n \n marks if factor of ½ used, taking into account orbital kinetic energies, leading to a final answer of 9.4 x 10\n \n 10\n \n «J».\n \n
\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n \n Award\n \n [2] marks\n \n for a bald correct answer.\n \n
\n\n A 4.0 cm length of a conducting wire carries a current of 2.5 A. The length is parallel to another long straight wire that carries a current of 10 A. The distance between the wires is 1.0 cm. The currents are in opposite directions.\n
\n\n What is the magnitude of the force and the direction of the force acting on the 4.0 cm length?\n
\n\n \n
\n
\n| \n | \n\n \n Magnitude of force / μN\n \n | \n\n \n Direction of force\n \n | \n
| \n A.\n | \n\n 1.3\n | \n\n Towards other wire\n | \n
| \n B.\n | \n\n 20\n | \n\n Towards other wire\n | \n
| \n C.\n | \n\n 1.3\n | \n\n Away from other wire\n | \n
| \n D.\n | \n\n 20\n | \n\n Away from other wire\n | \n
\n
\n\n [1]\n
\n\n D\n
\n\n A plate performs simple harmonic oscillations with a frequency of 39 Hz and an amplitude of 8.0 cm.\n
\n\n Show that the maximum speed of the oscillating plate is about 20 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n use of\n \n ✓\n
\n\n maximum speed is\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n There are eight wheels on each tram with a brake system for each wheel. A pair of brake pads clamp firmly onto an annulus made of steel.\n
\n\n The train comes to rest from speed\n \n v\n \n . Ignore the energy transferred to the brake pads and the change in the gravitational potential energy of the tram during the braking.\n
\n\n Calculate the temperature change in each steel annulus as the tram comes to rest.\n
\n\n Data for this question\n
\n\n The inner radius of the annulus is 0.40 m and the outer radius is 0.50 m.\n
\n\n The thickness of the annulus is 25 mm.\n
\n\n The density of the steel is 7860 kg m\n \n −3\n \n
\n\n The specific heat capacity of the steel is 420 J kg\n \n −1\n \n K\n \n −1\n \n
\n\n [4]\n
\n\n Work leading to volume = 7.1 x 10\n \n −3\n \n m\n \n 3\n \n ✓\n
\n\n Work leading to mass of steel = 55 .8 kg ✓\n
\n\n Kinetic Energy transferred per annulus =\n \n
\n\n = 110 kJ ✓\n
\n\n \n K ✓\n
\n\n Outline how this waste is treated after it has been removed from the fission reactor.\n
\n\n [4]\n
\n\n Waste (fuel rod) is placed in cooling ponds for a number of years ✓\n
\n\n After most active products have decayed the uranium is separated to be recycled/reprocessed ✓\n
\n\n The remaining highly active waste is vitrified / made into a solid form ✓\n
\n\n And stored (deep) underground ✓\n
\n\n Calculate the gradient of the graph.\n
\n\n [2]\n
\n\n large enough triangle Δ\n \n m\n \n ≥ 50 g✓\n
\n\n answer in range 0.210 − 0.240 «kg m\n \n −1\n \n » ✓\n
\n\n
\n\n \n Accept answers in g m\n \n −2\n \n .\n \n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n A typical interatomic distance in the graphite crystal is of the order of\n \n m. Estimate the minimum value of\n \n U\n \n for the pattern in (a) to be formed on the screen.\n
\n\n [4]\n
\n\n The de Broglie wavelength of the electrons should be comparable to or shorter than the interatomic distance /\n \n m ✓\n
\n\n Momentum of electrons\n \n «\n \n N s» ✓\n
\n\n Kinetic energy of electrons = «\n \n »\n \n «J» ✓\n
\n\n \n U\n \n = «\n \n »40 «V» ✓\n
\n\n State what is meant by an isolated system.\n
\n\n [1]\n
\n\n Neither mass nor energy is exchanged with the surroundings ✓\n
\n\n A list of four physical quantities is\n
\n\n How many scalar quantities are in this list?\n
\n\n A. 1\n
\n\n B. 2\n
\n\n C. 3\n
\n\n D. 4\n
\n\n [1]\n
\n\n C\n
\n\n Explain why intensity maxima are observed at X and Y.\n
\n\n [2]\n
\n\n two waves superpose/mention of superposition/mention of «constructive» interference ✔\n
\n\n they arrive in phase/there is a path length difference of an integer number of wavelengths ✔\n
\n\n Many candidates were able to discuss the interference that is taking place in this question, but few were able to fully describe the path length difference. That said, the quality of responses on this type of question seems to have improved over the last few examination sessions with very few candidates simply discussing the crests and troughs of waves.\n
\n\n \n \n Outline, with reference to the curve, why it is unsafe to drive a train across the bridge at 30 m s\n \n -1\n \n for this amount of damping.\n \n \n
\n\n [2]\n
\n\n \n 30 m s\n \n –1\n \n corresponds to\n \n f\n \n = 1.2 Hz ✔\n
\n \n
\n \n the amplitude of vibration is a maximum for this speed\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n corresponds to the resonant frequency ✔\n \n
\n\n The answers to this question were generally well presented and a correct argument was presented by almost all candidates. Resonance was often correctly referred to.\n
\n\n Photons of a certain frequency incident on a metal surface cause the emission of electrons from the surface. The intensity of the light is constant and the frequency of photons is increased. What is the effect, if any, on the number of emitted electrons and the energy of emitted electrons?\n
\n\n \n
\n [1]\n
\n\n B\n
\n\n A low discrimination index with the majority of candidates choosing option D when B is correct. Students tend to link the intensity of light to the number of photons but forget that it is the energy (per unit time per unit area) of the light so if the photon energy increases (frequency increases) then the number of photons must decrease.\n
\n\n Three quantities used to describe a light wave are\n
\n\n I. frequency\n
\n II. wavelength\n
\n III. speed.\n
\n Which quantities increase when the light wave passes from water to air?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n C\n
\n\n Show that the time taken for the ball to reach the surface of the table is about 0.2 s.\n
\n\n [1]\n
\n\n \n t\n \n = «\n \n =» 0.22 «s»\n
\n \n \n OR\n \n \n
\n \n t\n \n =\n \n \n ✓\n \n
\n\n \n Answer to 2 or more significant figures or formula with variables replaced by correct values.\n \n
\n\n Calculate, in terms of\n \n g\n \n , the maximum acceleration of P.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n the kinetic energy of particles in an ideal gas.\n
\n\n [1]\n
\n\n it is the temperature at which all the (random) motion stops\n
\n\n \n \n OR\n \n \n
\n\n at which all the motion can be extrapolated to stop\n
\n\n \n \n OR\n \n \n
\n\n at which the kinetic energy of all particles is zero ✓\n
\n\n An ideal gas is maintained at a temperature of 100 K. The variation of the pressure\n \n P\n \n and\n \n of the gas is shown.\n
\n\n \n
\n What is the quantity of the gas?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n This question tested candidate understanding of the relationship between the slope of a graph and the ideal gas law. SL candidates found this question more difficult than their HL counterparts, but in both groups of students, option C was the most frequent (and correct) answer.\n
\n\n Predict from the equation whether the value of\n \n found experimentally will be larger, the same or smaller than the value of\n \n calculated directly.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n \n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n centripetal force is larger «than\n \n » /\n \n is smaller «than centripetal»\n \n \n ✓\n \n
\n\n \n «so» experimental\n \n \n \n \n \n is smaller «than calculated value»\n \n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n \n \n (refers to graph)\n \n
\n \n
\n \n reference to «friction force is» a systematic error «and does not affect gradient»\n \n \n ✓\n \n
\n\n \n «so»\n \n \n \n \n \n is the same\n \n \n ✓\n \n
\n\n
\n\n \n \n MP2 awarded only with correct justification.\n
\n Candidates can gain zero, MP1 alone or full marks.\n \n \n
\n \n \n OWTTE\n \n \n
\n\n Most successful candidates chose to consider a single point then concluding that the calculated\n \n mr\n \n would be smaller than the real value as\n \n W\n \n < centripetal force, or even went into analysing the dependence of the frictional force with\n \n W\n \n . Many were able to deduce this. Some candidates thought that a graph would still have the same gradient (if friction was constant) and mentioned systematic error, so\n \n mr\n \n was not changed which was also accepted.\n
\n\n State\n \n two\n \n assumptions of your calculation in part (b).\n
\n\n [2]\n
\n\n No other forces than\n \n F\n \n provide the torque ✓\n
\n\n The thread unwinds without slipping ✓\n
\n\n The thread is weightless ✓\n
\n\n \n F\n \n is always tangent to the flywheel ✓\n
\n\n Outline\n \n two\n \n differences between the momentum of the box and the momentum of the load at the same instant.\n
\n\n [2]\n
\n\n direction of motion is different /\n \n \n OWTTE\n \n \n ✓\n
\n\n \n mv\n \n / magnitude of momentum is different «even though\n \n v\n \n the same» ✓\n
\n\n Many students recognized the vector nature of momentum implied in the question, although some focused on the forces acting on each object rather than discussing the momentum.\n
\n\n Show that the gravitational potential due to the planet and the star at the surface of the planet is about −5 × 10\n \n 9\n \n J kg\n \n −1\n \n .\n
\n\n [3]\n
\n\n \n V\n \n \n planet\n \n = «−»\n \n «−» 5.9 × 10\n \n 7\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n V\n \n \n star\n \n = «−»\n \n «−» 4.9 × 10\n \n 9\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n V\n \n \n planet\n \n +\n \n V\n \n \n star\n \n = «−» 4.9 «09» × 10\n \n 9\n \n «J kg\n \n −1\n \n »\n \n ✓\n \n
\n\n \n
\n \n \n Must see substitutions and not just equations.\n \n
\n Three forces act on a block which is sliding down a slope at constant speed.\n \n is the weight,\n \n is the reaction force at the surface of the block and\n \n is the friction force acting on the block.\n
\n\n \n
\n In this situation\n
\n\n A. there must be an unbalanced force down the plane.\n
\n\n B.\n \n .\n
\n\n C.\n \n .\n
\n\n D. the resultant force on the block is zero.\n
\n\n [1]\n
\n\n D\n
\n\n The tram travels at\n \n v\n \n throughout the journey. Two trams are available so that one is returning to the lower station on another line while the other is travelling to the village. The journeys take the same time.\n
\n\n It takes 1.5 minutes to unload and 1.5 minutes to load each tram. Ignore the time taken to accelerate the tram at the beginning and end of the journey.\n
\n\n Estimate the maximum number of passengers that can be carried up to the village in one hour.\n
\n\n [4]\n
\n\n Time for run =\n \n s/v\n \n = 3000 ÷ 13.2 = 227 s ✓\n
\n\n 3 minutes loading = 180 s\n
\n\n So one trip = 407 s ✓\n
\n\n And there are 3600/407 trips per hour = 8.84 ✓\n
\n\n So 8\n \n complete\n \n trips with 75 = 600 passengers ✓\n
\n\n The graph shows for model A the variation with\n \n of elastic potential energy\n \n E\n \n \n p\n \n stored in the spring.\n
\n\n \n
\n Describe the graph for model B.\n
\n\n [2]\n
\n\n same curve\n \n \n OR\n \n \n shape for small amplitudes «to about 0.05 m» ✓\n
\n\n for large amplitudes «outside of 0.05 m»\n \n E\n \n \n p\n \n smaller for model B / values are lower than original / spread will be wider ✓\n \n \n OWTTE\n \n \n
\n\n
\n\n \n Accept answers drawn on graph – e.g.\n \n
\n\n \n \n \n
\n Candidates were generally successful in describing one of the two aspects of the graph of B compared to A, but few were able to describe both. It should be noted that this is a two mark question, so candidates should have considered the fact that there are two distinct statements to be made about the graphs. Examiners did accept clearly drawn graphs as well for full marks.\n
\n\n The net is stretched across the middle of the table. The table has a length of 2.74 m and the net has a height of 15.0 cm.\n
\n\n Show that the ball will go over the net.\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n «0.114 s» ✓\n
\n\n \n m ✓\n
\n\n so (0.24 − 0.065) = 0.175 > 0.15\n \n \n OR\n \n \n 0.065 < (0.24 − 0.15) «so it goes over the net»\n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n «0.24 − 0.15 = 0.09 =\n \n so»\n \n t\n \n = 0.134 s\n \n ✓\n \n
\n\n 0.134 × 12 = 1.6 m\n \n ✓\n \n
\n\n 1.6 > 1.37 «so ball passed the net already»\n \n ✓\n \n
\n\n
\n\n \n Allow use of g = 9.8.\n \n
\n\n Calculate the maximum speed of the electrons in the beam.\n
\n\n [2]\n
\n\n use of ½\n \n mv\n \n \n 2\n \n =\n \n eV ✓\n \n
\n\n 1.33 × 10\n \n 7\n \n m s\n \n −1\n \n ✓\n
\n\n The graph shows the variation with distance\n \n of the displacement of the particles in a wave. The frequency of the wave is 600 Hz.\n
\n\n
\n \n
\n What is the speed of the wave?\n
\n\n
\n A. 0.012 m s\n \n −1\n \n
\n B. 0.024 m s\n \n −1\n \n
\n\n C. 1.2 m s\n \n −1\n \n
\n\n D. 2.4 m s\n \n −1\n \n
\n\n [1]\n
\n\n D\n
\n\n Outline the origin of the force that acts on Phobos.\n
\n\n [1]\n
\n\n gravitational attraction/force/field «of the planet/Mars» ✔\n
\n\n \n Do not accept “gravity”\n \n .\n
\n\n This was generally well answered, although some candidates simply used the vague term “gravity” rather than specifying that it is a gravitational force or a gravitational field. Candidates need to be reminded about using proper physics terms and not more general, “every day” terms on the exam.\n
\n\n The work done to move a particle of charge 0.25 μC from one point in an electric field to another is 4.5 μJ. Calculate the magnitude of the potential difference between the two points.\n
\n\n [1]\n
\n\n «\n \n » 18 «V» ✓\n
\n\n Show that the collision is inelastic.\n
\n\n [3]\n
\n\n initial energy 24 mJ and final energy 12 mJ ✔\n
\n\n energy is lost/unequal /change in energy is 12 mJ ✔\n
\n\n inelastic collisions occur when energy is lost ✔\n
\n
\n
\n Candidates fell into some broad categories on this question. This was a “show that” question, so there was an expectation of a mathematical argument. Many were able to successfully show that the initial and final kinetic energies were different and connect this to the concept of inelastic collisions. Some candidates tried to connect conservation of momentum unsuccessfully, and some simply wrote an extended response about the nature of inelastic collisions and noted that the bobs stuck together without any calculations. This approach was awarded zero marks.\n
\n\n \n When a wire with an electric current\n \n I\n \n is placed in a magnetic field of strength\n \n B\n \n it experiences a magnetic force\n \n F\n \n . What is the direction of\n \n F\n \n ?\n \n
\n\n \n A. In a direction determined by\n \n I\n \n only\n
\n \n
\n \n B. In a direction determined by\n \n B\n \n only\n
\n \n
\n \n C. In the plane containing\n \n I\n \n and\n \n B\n \n
\n \n
\n \n D. At 90° to the plane containing\n \n I\n \n and\n \n B\n \n \n
\n\n [1]\n
\n\n D\n
\n\n State the fundamental SI units for permeability of free space,\n \n .\n
\n\n [1]\n
\n\n kg m s\n \n −2\n \n A\n \n −2\n \n ✓\n
\n\n Explain why the received intensity varies between maximum and minimum values.\n
\n\n [3]\n
\n\n movement of B means that path distance is different « between BM and AM »\n
\n \n \n OR\n \n \n
\n movement of B creates a path difference «between BM and AM» ✓\n
\n interference\n
\n \n \n OR\n \n \n
\n superposition «of waves» ✓\n
\n maximum when waves arrive in phase / path difference = n x lambda\n
\n \n \n OR\n \n \n
\n minimum when waves arrive «180° or\n \n » out of phase / path difference = (n+½) x lambda ✓\n
\n This was an \"explain\" questions, so examiners were looking for a clear discussion of the movement of speaker B creating a changing path difference between B and the microphone and A and the microphone. This path difference would lead to interference, and the examiners were looking for a connection between specific phase differences or path differences for maxima or minima. Some candidates were able to discuss basic concepts of interference (e.g. \"there is constructive and destructive interference\"), but failed to make clear connections between the physical situation and the given graph. A very common mistake candidates made was to think the question was about intensity and to therefore describe the decrease in peak height of the maxima on the graph. Another common mistake was to approach this as a Doppler question and to attempt to answer it based on the frequency difference of B.\n
\n\n Outline why the angular speed\n \n ω\n \n decreases when the spheres move outward.\n
\n\n [2]\n
\n\n moment of inertia increases ✓\n
\n\n Angular momentum is conserved ✓\n
\n\n \n
\n Allow algebraic expressions e.g. ω =\n \n so ω decreases for\n \n MP2\n \n \n
\n Determine the magnitude and direction of the resultant magnetic field at Q.\n
\n\n [2]\n
\n\n «using components or Pythagoras to get»\n \n B\n \n = 21 «mT» ✓\n
\n\n directed «horizontally» to the right ✓\n
\n\n
\n\n \n If no unit seen, assume\n \n mT.\n
\n\n A sample of glass is irradiated with neutrons so that all the magnesium atoms become magnesium-27. The sample contains 9.50 × 10\n \n 15\n \n magnesium atoms.\n
\n\n The decay constant of magnesium-27 is 1.22 × 10\n \n −3\n \n s\n \n −1\n \n .\n
\n\n Determine the number of aluminium atoms that form in 10.0 minutes after the irradiation ends.\n
\n\n [3]\n
\n\n \n N\n \n \n 10\n \n = 9.50 × 10\n \n 15\n \n ×\n \n e\n \n \n −0.00122×60\n \n seen ✓\n
\n\n \n N\n \n \n 10\n \n = 4.57 × 10\n \n 15\n \n ✓\n
\n\n So number of aluminium-27 nuclei = (9.50 – 4.57) × 10\n \n 15\n \n = 4.9(3) × 10\n \n 15\n \n ✓\n
\n\n The frequency of the generator is doubled with no other changes being made. Draw, on the axes, the variation with time of the voltage output of the generator.\n
\n\n [2]\n
\n\n \n peak emf doubles\n \n \n ✓\n \n
\n\n \n \n \n \n halves\n \n \n ✓\n \n
\n\n \n \n
\n Must show at least 1 cycle.\n \n \n
\n Well answered, with the majority of candidates scoring at least 1 mark.\n
\n\n A ball of mass 1.5 kg strikes a force sensor and bounces. The ball experiences a change in velocity of 10 m s\n \n −1\n \n . The graph shows the variation with time\n \n t\n \n of the force\n \n F\n \n recorded by the sensor.\n
\n\n
\n\n \n
\n What is Δ\n \n T\n \n ?\n
\n\n
\n A. 0.15 s\n
\n B. 0.30 s\n
\n\n C. 0.60 s\n
\n\n D. 3.0 s\n
\n\n [1]\n
\n\n B\n
\n\n This question was very poorly answered, with over 50% of the candidates choosing incorrect alternative A. In fact, the question tests understanding of a relatively simple idea that the area under a force-time graph represents the change in momentum of the particle. Students need practice in evaluating areas of simple shapes and applying geometry in the context of physics graphs.\n
\n\n The molar mass of water is 18 g mol\n \n −1\n \n . Estimate the average speed of the water molecules in the vapor produced. Assume the vapor behaves as an ideal gas.\n
\n\n [2]\n
\n\n \n E\n \n \n k\n \n = «\n \n » =\n \n «J»\n \n ✓\n \n
\n\n \n v =\n \n «\n \n \n \n »\n \n =\n \n 720 «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n Star X has the same surface temperature as the Sun and a luminosity of\n \n
\n\n What is\n \n ?\n
\n\n
\n A. 10\n
\n B. 10\n \n 2\n \n
\n\n C. 10\n \n 3\n \n
\n\n D. 10\n \n 4\n \n
\n\n [1]\n
\n\n B\n
\n\n \n The frequency of the oscillator is reduced to 120 Hz. On the diagram, draw the standing wave that will be formed on the string.\n \n
\n\n \n
\n [1]\n
\n\n \n first harmonic mode drawn ✔\n \n
\n\n \n \n \n
\n \n \n NOTE: Allow if only one curve drawn, either solid or dashed.\n \n \n
\n\n The temperatures are now reversed so that X is at 45 °C and Z is at 90 °C. Show that the rate of energy transfer is unchanged.\n
\n\n [2]\n
\n\n repeats calculation to show that\n \n θ\n \n = 75 °C ✓\n
\n\n temperature difference across YZ is still 15 K which gives the same rate of energy transfer (but in opposite direction) ✓\n
\n\n Calculate, for the surface of\n \n , the gravitational field strength\n \n g\n \n \n Io\n \n due to the mass of\n \n . State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n N kg\n \n −1\n \n \n \n OR\n \n \n m s\n \n −2\n \n \n ✓\n \n
\n\n State the main element that is undergoing nuclear fusion in star C.\n
\n\n [1]\n
\n\n Hydrogen ✓\n
\n\n Three statements about Newton’s law of gravitation are:\n
\n\n I. It can be used to predict the motion of a satellite.\n
\n II. It explains why gravity exists.\n
\n III. It is used to derive the expression for gravitational potential energy.\n
\n Which combination of statements is correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n Comments suggested that 'gravitational potential' is more suitable for an HL question. However, candidates should have realised that statement II is incorrect so option B is the only possibility and this proved the most popular answer. The wording will be altered to 'gravitational potential energy' for publication.\n
\n\n The frequency of the wave is 0.50 Hz. Calculate the speed of the wave.\n
\n\n [1]\n
\n\n \n v\n \n = «0.50 × 16 =» 8.0 «m s\n \n −1\n \n » ✓\n
\n\n The maximum intensity of sunlight incident on the photovoltaic cell at the place on the Earth’s surface is 680 W m\n \n −2\n \n .\n
\n\n A measure of the efficiency of a photovoltaic cell is the ratio\n
\n\n \n
\n\n Determine the efficiency of this photovoltaic cell when the intensity incident upon it is at a maximum.\n
\n\n [3]\n
\n\n power arriving at cell = 680 x 0.35 x 0.45 = «107 W»\n \n ✓\n \n
\n\n power in external circuit = 14.5 x 0.9 = «13.1 W»\n \n ✓\n \n
\n\n efficiency = 0.12\n \n \n OR\n \n \n 12 %\n \n ✓\n \n
\n\n \n
\n Award\n \n [3] marks\n \n for a bald correct answer\n \n
\n \n Allow\n \n ECF\n \n for\n \n MP3\n \n \n
\n\n Show that the temperature of the gas at C is approximately 350 °C.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n use of\n \n = constant «so\n \n » ✓\n
\n\n \n T\n \n \n C\n \n = 624 «K»\n \n \n OR\n \n \n \n T\n \n \n C\n \n = 351 «°C» ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n use of\n \n to get either\n \n p\n \n \n c\n \n =\n \n \n \n OR\n \n \n \n p\n \n \n c\n \n = 268 «kPa» ✓\n
\n\n «\n \n T\n \n \n C\n \n = 268 × 300/129 = so »\n
\n\n \n T\n \n \n C\n \n = 624 «K»\n \n \n OR\n \n \n \n T\n \n \n C\n \n = 351 «°C» ✓\n
\n\n A book of mass\n \n m\n \n lies on top of a table of mass\n \n M\n \n that rolls freely along the ground. The coefficient of friction between the book and the table is\n \n \n \n . A person is pushing the rolling table.\n
\n\n What is the maximum acceleration of the table so that the book does not slide backwards relative to the table?\n
\n\n \n
\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Over half the candidates incorrectly chose option D. The book is only able to accelerate because of the friction force between the table and the book which depends on μ and the normal reaction force (mg) so independent of M, immediately eliminating options C and D.\n
\n\n A pure sample of radioactive nuclide\n \n decays into a stable nuclide\n \n .\n
\n\n What is\n \n after two half-lives?\n
\n\n
\n A. 1\n
\n B. 2\n
\n\n C. 3\n
\n\n D. 4\n
\n\n [1]\n
\n\n C\n
\n\n Determine the moment of inertia of the system about the central axis.\n
\n\n [2]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n 33 =\n \n × 4 ✓\n
\n\n
\n\n \n = 8.25 «kg m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (a)\n \n and\n \n (b)\n \n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n \n
\n\n \n An electron is fixed in position in a uniform electric field. What is the position for which the electrical potential energy of the electron is greatest?\n \n
\n\n \n \n \n
\n [1]\n
\n\n D\n
\n\n Calculate the angular impulse applied to the flywheel.\n
\n\n [2]\n
\n\n Attempt to find area of triangle ✓\n
\n\n \n «kg m\n \n 2\n \n s\n \n −1\n \n » ✓\n
\n\n Show that the volume at C is 3.33 × 10\n \n −2\n \n m\n \n 3\n \n .\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Use of adiabatic formula «\n \n »\n \n ✓\n
\n\n \n × 2.00 × 10\n \n −3\n \n «= 3.333 × 10\n \n −2\n \n m\n \n 3\n \n » ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , working or answer to at least 4 SF must be seen.\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n p\n \n \n A\n \n \n V\n \n \n A\n \n =\n \n p\n \n \n B\n \n \n V\n \n \n B\n \n ✓\n
\n\n \n ✓\n
\n\n
\n\n \n \n ALTERNATIVE 3\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n n\n \n = 0.2 mol ✓\n
\n\n \n V\n \n \n C\n \n = (0.2 × 8.31 × 602) / 4 × 10\n \n 4\n \n ✓\n
\n\n Use the graph to show that the nuclear radius of silicon-30 is about 4 fm.\n
\n\n [3]\n
\n\n read off between 17 and 19 «deg» ✔\n
\n\n correct use of\n \n d\n \n =\n \n \n \n \n \n = 7.8 × 10\n \n −15\n \n «m» ✔\n
\n\n so radius =\n \n \n \n «fm» = 3.9 «fm» ✔\n
\n\n \n Award ecf for wrong angle in MP1.\n \n
\n\n \n Answer for MP3 must show at least 2\n \n \n sf.\n \n
\n\n This question was left blank by many candidates and many of those who attempted it chose an angle that when used with the correct equation gave an answer close to the given answer of 4 fm. Very few selected the correct angle, calculated the correct diameter, and divided by two to get the correct radius.\n
\n\n Calculate the torque acting on the bar while it is accelerating.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n The students vary\n \n V\n \n and measure the time\n \n T\n \n for the ball to move\n \n once\n \n from one plate to the other. The table shows some of the data.\n
\n\n \n
\n
\n\n 0.02 «kV» ✓\n
\n\n \n In the reference frame of the train a ball travels with speed 0.50\n \n c\n \n from the back to the front of the train, as the train passes the platform. Calculate the time taken for the ball to reach the front of the train in the reference frame of the platform.\n \n
\n\n [3]\n
\n\n \n \n \n ALTERNATIVE 1:\n \n \n \n \n
\n \n
\n \n \n \n
\n \n \n \n \n ALTERNATIVE 2:\n \n \n \n \n
\n\n \n \n \n \n v\n \n of ball is 0.846\n \n c\n \n for platform ✔\n
\n \n \n \n
\n \n \n \n length of train is 68m for platform ✔\n \n \n \n
\n\n \n \n \n \n \n \n \n
\n \n \n \n \n \n ALTERNATIVE 3:\n \n \n \n \n \n
\n\n \n
\n Almost no candidates could use a Lorentz transformation to find the time of the ball’s travel in the frame of reference of the platform. Most just applied some form of t=γt’. Elapsed time and instantaneous time in different frames were easily confused. Candidates rarely mention which reference frame is used when making calculations, however this is crucial in relativity.\n
\n\n Show that the intensity of the solar radiation at the location of Titan is 16 W m\n \n −2\n \n
\n\n [1]\n
\n\n incident intensity\n \n \n \n OR\n \n \n \n «W m\n \n −2\n \n » ✓\n
\n\n
\n\n \n Allow the use of 1400 for the solar constant.\n \n
\n\n Explain why a centripetal force is needed for the planet to be in a circular orbit.\n
\n\n [2]\n
\n\n «circular motion» involves a changing velocity\n \n ✓\n \n
\n\n «Tangential velocity» is «always» perpendicular to centripetal force/acceleration\n \n ✓\n \n
\n\n there must be a force/acceleration towards centre/star\n \n ✓\n \n
\n\n without a centripetal force the planet will move in a straight line\n \n ✓\n \n
\n\n The graph shows the variation with distance of a horizontal force acting on an object. The object, initially at rest, moves horizontally through a distance of\n \n .\n
\n\n \n
\n A constant frictional force of\n \n opposes the motion. What is the final kinetic energy of the object after it has moved\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Calculate the average translational speed of air molecules.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «m s\n \n −1\n \n » ✓\n
\n\n Outline why the pattern observed on the screen is an evidence for matter waves.\n
\n\n [2]\n
\n\n The pattern is formed when the electrons scattered from adjacent planes in the graphite crystal undergo interference / diffract ✓\n
\n\n Interference / diffraction is a property of waves only ✓\n
\n\n Determine the magnetic force acting on the 15 Ω wire due to the current in the 30 Ω wire.\n
\n\n [4]\n
\n\n Use of combination of resistors OR\n \n ✓\n
\n\n To show that current in 30 Ω wire is 5.0 A ✓\n
\n\n \n ✓\n
\n\n \n N ✓\n
\n\n Determine the kinetic energy of the ball immediately after the bounce.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n KE =\n \n \n mv\n \n \n 2\n \n +\n \n mgh\n \n =\n \n 0.0027 ×10.5\n \n 2\n \n + 0.0027 × 9.8 × 0.18\n \n ✓\n \n
\n\n 0.15 «J»\n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n Use of\n \n v\n \n \n x\n \n = 10.5\n \n \n AND\n \n \n \n v\n \n \n y\n \n \n =\n \n 1.88 to get\n \n v\n \n = «\n \n » = 10.67 «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n KE =\n \n × 0.0027 × 10.67\n \n 2\n \n = 0.15 «J»\n \n ✓\n \n
\n\n A satellite is orbiting Earth in a circular path at constant speed. Three statements about the resultant force on the satellite are:\n
\n\n I. It is equal to the gravitational force of attraction on the satellite.\n
\n II. It is equal to the mass of the satellite multiplied by its acceleration.\n
\n III. It is equal to the centripetal force on the satellite.\n
\n Which combination of statements is correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n This was a good discriminator at HL although many candidates chose option B (D correct). Option B was just the most popular choice at SL. Candidates appear not to realise that although this is circular motion\n \n F = ma\n \n still applies.\n
\n\n Outline how the concept of absolute zero of temperature is interpreted in terms of:\n
\n\n
\n\n it is the temperature at which the volume\n
\n\n \n \n OR\n \n \n
\n\n the pressure extrapolates to zero (can be shown by sketch) ✓\n
\n\n An object of mass\n \n is thrown downwards from a height of\n \n . The initial speed of the object is\n \n .\n
\n The object hits the ground at a speed of\n \n . Assume\n \n . What is the best estimate of the energy transferred from the object to the air as it falls?\n
\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Monochromatic light of wavelength 633 nm is normally incident on a diffraction grating. The diffraction maxima incident on a screen are detected and their angle\n \n θ\n \n to the central beam is determined. The graph shows the variation of sin\n \n θ\n \n with the order\n \n n\n \n of the maximum. The central order corresponds to\n \n n\n \n = 0.\n
\n\n \n
\n Determine a mean value for the number of slits per millimetre of the grating.\n
\n\n [4]\n
\n\n identifies gradient with\n \n \n \n OR\n \n \n use of\n \n \n ✓\n \n
\n\n gradient = 0.08\n \n \n OR\n \n \n correct replacement in equation with coordinates of a point\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from\n \n MP3\n \n \n
\n Which property of a nuclide does\n \n not\n \n change as a result of beta decay?\n
\n\n A. Nucleon number\n
\n\n B. Neutron number\n
\n\n C. Proton number\n
\n\n D. Charge\n
\n\n [1]\n
\n\n A\n
\n\n Response A was the most common (correct) response from a minority of candidates (38 %). Incorrect responses were evenly divided among the remaining options.\n
\n\n Calculate the ratio\n \n \n \n \n \n where\n \n V\n \n C\n \n \n is the volume of the gas at C and\n \n V\n \n B\n \n \n is the volume at B.\n
\n\n [2]\n
\n\n \n \n \n \n \n ✔\n
\n\n \n \n \n \n \n ✔\n
\n\n \n Award\n \n [2]\n \n for bald correct answer.\n \n
\n\n The efficiency of the Carnot cycle was well calculated by most of the candidates, but the thermal energy that leaves the gas was well calculated only by the best candidates. Many candidates were able to establish that the heat added to the gas was 540 J - but struggled to then link this with the efficiency to determine the thermal energy leaving the gas. In iii) the better candidates used the formula given at i) to appropriately calculate the ratio but many were not able to manipulate the expressions to achieve the desired outcome. The reciprocal of 2.5 (0.4) was a common error in the final result and so was the incorrect use of the formula for isobaric expansion. The change in the entropy was well calculated by many candidates with ECF being very prominent from part biii). A complete and proper explanation in ii) was well formulated only by the better candidates. However, many were able to recognize that the Carnot engine was ideal and not real. Many answers referred to heat being lost to the environment but not to “additional losses” that make the engine less than its ideal capacity.\n
\n\n Three current-carrying wires lie in the same plane and carry currents of 6 A, 2 A and 4 A. The currents are all in the same direction.\n
\n\n The 2 A wire is 4 cm from the 4 A wire and 6 cm from the 6 A wire.\n
\n\n \n
\n What magnetic force per unit length acts on the 2 A wire?\n
\n\n
\n A. 0\n
\n B. 40 μN m\n \n −1\n \n
\n\n C. 80 μN m\n \n −1\n \n
\n\n D. 160 μN m\n \n −1\n \n
\n\n [1]\n
\n\n A\n
\n\n A quantity of an ideal gas is at a temperature\n \n T\n \n in a cylinder with a movable piston that traps a length\n \n L\n \n of the gas. The piston is moved so that the length of the trapped gas is reduced to\n \n and the pressure of the gas doubles.\n
\n\n \n
\n What is the temperature of the gas at the end of the change?\n
\n\n
\n A.\n \n
\n
\n B.\n \n
\n
\n C.\n \n
\n
\n D.\n \n
\n [1]\n
\n\n C\n
\n\n Some comments queried that the Laws of Thermodynamics are not on the syllabus. This question was set as a test of Thermal Physics, topic 3, with option A coming from Mechanics, topic 2, not Thermodynamics.\n
\n\n A standing wave is formed in a pipe open at one end and closed at the other. The length of the pipe is\n \n L\n \n and the speed of sound in the pipe is\n \n V\n \n .\n
\n\n \n
\n \n n\n \n is a positive integer.\n
\n\n What expression is correct about the frequencies of the harmonics in the pipe?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n \n Calculate, in m s\n \n –1\n \n , the speed for this wave.\n \n
\n\n [1]\n
\n\n \n v =\n \n \n «\n \n » 250 «m s\n \n –1\n \n »✔\n \n
\n\n Show that the energy of the scattered photon is about 16 keV.\n
\n\n [1]\n
\n\n \n «= 15.9 keV» ✓\n
\n\n The nucleus of the isotope hydrogen-2 has a radius\n \n R\n \n and a density\n \n \n \n .\n
\n\n What are the approximate radius and density of a nucleus of oxygen-16?\n
\n\n
\n \n
\n [1]\n
\n\n A\n
\n\n In another situation the rod rests on a horizontal frictionless surface with no pivot. Predict, without calculation, the motion of the rod–particle system after the collision.\n
\n\n [2]\n
\n\n the rod will rotate «about centre of mass» ✓\n
\n\n «centre of mass» will move along straight line\n
\n «parallel to the particle’s initial velocity» ✓\n
\n
\n\n \n For\n \n MP2\n \n , mention of translational motion is not enough.\n \n
\n\n A stone is kicked horizontally at a speed of 1.5 m s\n \n −1\n \n from the edge of a cliff on one of Jupiter’s moons. It hits the ground 2.0 s later. The height of the cliff is 4.0 m. Air resistance is negligible.\n
\n\n What is the magnitude of the displacement of the stone?\n
\n\n \n
\n A. 7.0 m\n
\n\n B. 5.0 m\n
\n\n C. 4.0 m\n
\n\n D. 3.0 m\n
\n\n [1]\n
\n\n B\n
\n\n This question was generally well answered by both HL and SL candidates and had a mid-range difficulty index (indicating an easier question). Option D was an effective distractor for candidates calculating the horizontal range rather than the displacement. Candidates are encouraged to read the questions carefully to ensure it is clear what each question is asking for.\n
\n\n Object X collides with object Y. Y is initially stationary. The tracks of the colliding particles after the collision are shown.\n
\n\n Which collision is elastic?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n A sample of oxygen gas with a volume of\n \n is at\n \n . The gas is heated so that it expands at a constant pressure to a final volume of\n \n . What is the final temperature of the gas?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n State the nature and direction of the force that accelerates the 15 kg object.\n
\n\n [1]\n
\n\n static friction force «between blocks»\n
\n\n \n \n AND\n \n \n
\n\n directed to the right ✓\n
\n\n \n The gravitational potential is\n \n \n \n at a distance\n \n \n \n above the surface of a spherical planet of radius\n \n \n \n and uniform density. What is the gravitational potential a distance\n \n above the surface of the planet?\n \n
\n\n \n A.\n \n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n \n D.\n \n \n
\n\n [1]\n
\n\n D\n
\n\n Calculate the angular impulse applied to the flywheel.\n
\n\n [2]\n
\n\n Attempt to find area of triangle ✓\n
\n\n \n «kg m\n \n 2\n \n s\n \n −1\n \n » ✓\n
\n\n White dwarfs with similar volumes to each other are shown on the HR diagram.\n
\n\n Sketch, on the HR diagram, to show the possible positions of other white dwarf stars with similar volumes to those marked on the HR diagram.\n
\n\n [2]\n
\n\n Any evidence of correct identification that three dots bottom left represent white dwarfs ✓\n
\n\n line passing through all 3 white dwarfs\n \n \n OR\n \n \n line continuing from 3 white dwarfs with approximately same gradient, in either direction ✓\n
\n\n
\n\n \n Award\n \n MP2\n \n if no line drawn through the three dots but just beyond them in either direction\n \n
\n\n The metal plate is replaced by a wooden plate that reflects a lower intensity sound wave than the metal plate.\n
\n\n State and explain the differences between the sound intensities detected by the same microphone with the metal plate and the wooden plate.\n
\n\n [3]\n
\n\n relates intensity to amplitude ✓\n
\n\n antinodes / maximum intensity will be decreased / quieter ✓\n
\n\n nodes / minimum will be increased / louder ✓\n
\n\n difference in intensities will be less ✓\n
\n\n maxima and minima are at the same positions ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n A projectile is launched upwards at an angle\n \n θ\n \n to the horizontal with an initial momentum\n \n p\n \n \n 0\n \n and an initial energy\n \n E\n \n \n 0\n \n . Air resistance is negligible. What are the momentum and total energy of the projectile at the highest point of the motion?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Show, using the data, that the energy released in the decay of one magnesium-27 nucleus is about 2.62 MeV.\n
\n\n Mass of aluminium-27 atom = 26.98153 u\n
\n Mass of magnesium-27 atom = 26.98434 u\n
\n The unified atomic mass unit is 931.5 MeV c\n \n −2\n \n .\n
\n [1]\n
\n\n (26.98434 - 26.98153) × 931.5\n
\n\n \n \n OR\n \n \n
\n\n 2.6175 «MeV» seen ✓\n
\n\n The block falls a distance 0.50 m after its release before hitting the ground. Show that the block hits the ground 0.55 s after release.\n
\n\n [2]\n
\n\n \n a\n \n = 3.27 «ms\n \n −2\n \n » /\n \n a\n \n =\n \n g\n \n /3 ✔\n
\n\n \n \n \n \n \n ✔\n
\n\n = 0.55 «s»\n
\n\n \n Do not apply ECF from MP1 to MP2 if for a=g, giving answer 0.32 s\n \n .\n
\n\n The application of the uniformly accelerated motion to this context was mastered successfully by better candidates.\n
\n\n \n Calculate the ratio\n \n .\n \n
\n\n [2]\n
\n\n \n states or applies conservation of momentum ✔\n \n
\n\n \n ratio is «\n \n » 58.5\n \n ✔\n \n
\n \n
\n \n NOTE: Award\n \n [2]\n \n for bald correct answer\n \n
\n\n Calculate, for the cylinder, at the instant just before the block hits the ground the angular momentum.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n
\n \n
\n Δ\n \n L\n \n «= ΓΔ\n \n t\n \n =\n \n TR\n \n Δ\n \n t\n \n » =\n \n \n \n \n \n \n \n ✔\n
\n\n Δ\n \n L =\n \n 2.2J «Js»✔\n \n
\n \n
\n \n \n ALTERNATIVE 2\n \n \n
\n\n ω =<\n \n \n \n Δ\n \n t =\n \n \n \n \n \n Δt =\n \n \n \n \n \n \n = > 8.99 «rads\n \n −1\n \n » ✔\n
\n\n \n ΔL\n \n «=\n \n Iω\n \n »\n \n \n \n \n \n × 12 × 0.20\n \n 2\n \n × 8.99 = 2.2 «\n \n Js\n \n »\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n Angular speed, angular momentum and the kinetic energy of the cylinder at the instant given were successfully calculated by only the better-prepared candidates. Students were mostly able to recognize the correct expressions to use but struggled to find the angular speed in many instances. Error carried forward was very common throughout this question for students who incorrectly determined the angular velocity but understood and correctly applied the momentum and energy equations.\n
\n\n \n Show that the total energy of the planet is given by the equation shown.\n \n
\n\n \n \n \n \n \n
\n\n [2]\n
\n\n \n \n \n \n ✔\n \n
\n\n \n comparison with\n \n \n \n \n ✔\n \n \n
\n\n \n «to give answer»\n \n
\n\n
\n\n This was generally well answered but with candidates sometimes getting in to trouble over negative signs but otherwise producing well-presented answers.\n
\n\n A sample of a gas has volume\n \n \n \n and contains\n \n \n \n molecules, each of mass\n \n \n \n . The average translational speed of the molecules is\n \n \n \n .\n
\n\n Which expression is equivalent to the pressure of the gas?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Both wires are 7.5 m long and are 0.25 m apart. The current in both wires is 12 A. Determine the force that acts on one wire due to the other.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n In practice, air resistance affects the ball. Outline the effect that air resistance has on the vertical acceleration of the ball. Take the direction of the acceleration due to gravity to be positive.\n
\n\n [2]\n
\n\n air resistance opposes «direction of» motion\n
\n \n \n OR\n \n \n
\n air resistance opposes velocity\n \n ✓\n \n
\n on the way up «vertical» acceleration is increased\n \n \n OR\n \n \n greater than g\n \n ✓\n \n
\n\n on the way down «vertical» acceleration is decreased\n \n \n OR\n \n \n smaller than g\n \n ✓\n \n
\n\n \n
\n Allow deceleration/acceleration but meaning must be clear\n \n
\n Outline why this force does no work on the Moon.\n
\n\n [1]\n
\n\n the force/field and the velocity/displacement are at 90° to each other\n \n \n OR\n \n \n there is no change in GPE of the moon ✔\n
\n\n \n Award\n \n [0]\n \n for any mention of no net force on the satellite.\n \n
\n\n \n Do not accept acceleration is perpendicular to velocity.\n \n
\n\n Some candidates connected the idea that the gravitational force is perpendicular to the velocity (and hence the displacement) for the mark. It was also allowed to discuss that there is no change in gravitational potential energy, so therefore no work was being done. It was not acceptable to simply state that the net displacement over one full orbit is zero. Unfortunately, some candidates suggested that there is no net force on the moon so there is no work done, or that the moon is so much smaller so no work could be done on it.\n
\n\n Show that the energy of the scattered photon is about 16 keV.\n
\n\n [1]\n
\n\n \n «= 15.9 keV» ✓\n
\n\n Outline why the magnetic flux in ring B increases.\n
\n\n [1]\n
\n\n ring B cuts an increasing number of magnetic field lines ✓\n
\n\n \n OR\n \n
\n\n magnetic field from current in A increases at the position of B ✓\n
\n\n The energy levels\n \n E\n \n of an atom are shown.\n
\n\n \n
\n Which emission spectrum represents the transitions?\n
\n\n
\n \n
\n [1]\n
\n\n D\n
\n\n the angular deceleration of the rod.\n
\n\n [1]\n
\n\n \n =\n \n = 0.603 rads\n \n −2\n \n ✓\n
\n\n
\n\n \n Accept negative values.\n \n
\n\n \n X and Y are two plane coils parallel to each other that have a common axis. There is a constant direct current in Y.\n \n
\n\n \n \n \n
\n \n \n X is first moved towards Y and later is moved away from Y. What, as X moves, is the direction of the current in X relative to that in Y?\n \n \n
\n\n \n
\n [1]\n
\n\n C\n
\n\n The intensity of light at point O is\n \n . The distance OP is\n \n .\n
\n\n Sketch, on the axes, a graph to show the variation of the intensity of light with distance from point O on the screen. Your graph should cover the distance range from 0 to 2\n \n .\n
\n\n \n
\n [2]\n
\n\n smooth curve decreasing from\n \n to 0 between 0 and\n \n ✓\n
\n\n secondary maximum correctly placed\n \n \n AND\n \n \n of intensity less than 0.3\n \n ✓\n
\n\n \n E.g.\n \n \n
\n Most scored MP1. Many candidates scored full marks but it was common to see a maximum at 2x or a secondary maxima too high.\n
\n\n A travelling wave has a frequency of\n \n . The closest distance between two points on the wave that have a phase difference of\n \n is\n \n . What is the speed of the wave?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Calculate the work done during the compression.\n
\n\n [1]\n
\n\n \n «\n \n \n –\n \n \n »\n \n \n \n \n \n «\n \n »\n \n \n ✓\n \n
\n\n
\n\n A constant torque acts on a bicycle wheel. The wheel accelerates from rest to a final angular velocity of 16 rad s\n \n −1\n \n in a time of 4.0 s.\n
\n\n What is the angular displacement of the wheel during the acceleration?\n
\n\n
\n A. 16 rad\n
\n B. 32 rad\n
\n\n C. 48 rad\n
\n\n D. 64 rad\n
\n\n [1]\n
\n\n B\n
\n\n \n Use your answer to (a)(ii) to describe the paradigm shift that Einstein’s theory of special relativity produced.\n \n
\n\n [2]\n
\n\n \n \n c\n \n is the same in all frames\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n \n c\n \n is maximum velocity possible ✔\n
\n \n
\n \n velocity addition frame dependent ✔\n
\n \n
\n \n length/time/mass/fields relative measurements ✔\n
\n \n
\n \n Newtonian/Galilean mechanics valid only at low speed ✔\n \n
\n\n Most candidates correctly stated that in special relativity the velocity of light, c, is the maximum possible velocity or is invariant. Only a few added that Galilean relativity only applies at speeds much less than the speed of light.\n
\n\n \n Suggest why this cycle is not a suitable model for a working heat pump.\n \n
\n\n [2]\n
\n\n \n the temperature changes in the cycle are too large ✔\n
\n \n
\n \n the cycle takes too long «because it contains an isothermal stage» ✔\n
\n \n
\n \n energy/power output would be too small ✔\n \n
\n\n Because the question was about a heat pump rather than a heat engine very few answers were correct. Only a very small number of candidates mentioned the fact that the isothermal change would take an impracticably long time.\n
\n\n \n Show that the electric field strength due to the point charge at the position of the electron is 3.4 × 10\n \n 8\n \n N C\n \n –1\n \n .\n \n
\n\n [2]\n
\n\n \n \n ✔\n \n
\n\n \n \n \n OR\n \n \n \n \n \n ✔\n \n \n
\n\n \n NOTE:\n \n Ignore any negative sign.\n \n \n
\n\n The rest mass of the helium isotope\n \n \n \n \n \n is\n \n m\n \n .\n
\n\n Which expression gives the binding energy per nucleon for\n \n \n \n \n \n ?\n
\n\n A.\n \n \n \n \n \n
\n\n \n B.\n \n \n \n \n
\n\n \n C.\n \n \n \n \n
\n\n \n D.\n \n \n \n \n \n \n
\n\n
\n\n [1]\n
\n\n B\n
\n\n \n Calculate the magnitude of the initial acceleration of the electron.\n \n
\n\n [2]\n
\n\n \n \n \n OR\n \n \n \n \n \n ✔\n \n \n
\n\n \n \n \n \n ✔\n \n \n \n
\n\n \n \n NOTE: Ignore any negative sign.\n
\n Award\n \n [1]\n \n for a calculation leading to\n \n \n \n \n \n \n \n
\n Award\n \n [2]\n \n for bald correct answer\n \n \n
\n
\n\n Determine the speed of the spaceship relative to Earth.\n
\n\n [1]\n
\n\n 0.6 c\n
\n\n \n \n OR\n \n \n
\n\n = 1.8 × 10\n \n 8\n \n «m s\n \n −1\n \n » ✓\n
\n\n \n Define an\n \n inertial reference frame.\n \n \n
\n\n [1]\n
\n\n \n a coordinate system which is not accelerating/has constant velocity/Newtons 1st law applies ✔\n \n
\n\n \n \n OWTTE\n \n \n
\n\n \n \n Both “inertial” and “reference frame” need to be defined\n \n \n
\n\n In defining an inertial frame of reference far too many candidates started with the words ‘ a frame of reference that...... ’ instead of ‘a coordinate system that.....’\n
\n\n \n A climber of mass\n \n m\n \n slides down a vertical rope with an average acceleration\n \n a\n \n . What is the average frictional force exerted by the rope on the climber?\n
\n \n
\n \n A.\n \n mg\n \n
\n \n
\n \n B.\n \n m\n \n (\n \n g + a\n \n )\n
\n \n
\n \n C.\n \n m\n \n (\n \n g – a\n \n )\n
\n \n
\n \n D.\n \n ma\n \n \n
\n\n [1]\n
\n\n C\n
\n\n escape speed from its orbit.\n
\n\n [1]\n
\n\n «\n \n = »\n \n ✓\n
\n\n In a photoelectric effect experiment, a beam of light is incident on a metallic surface W in a vacuum.\n
\n\n \n
\n The graph shows how the current\n \n \n \n varies with the potential difference\n \n V\n \n when three different beams X, Y, and Z are incident on W at different times.\n
\n\n \n
\n I. X and Y have the same frequency.\n
\n II. Y and Z have different intensity.\n
\n III. Y and Z have the same frequency.\n
\n Which statements are correct?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n C\n
\n\n Draw lines to indicate R on the diagram.\n
\n\n [2]\n
\n\n \n
\n R located at (4,4) ✓\n
\n\n «as intersection of» vertical line through 4 ly and photon worldline at 45 degrees✓\n
\n\n
\n\n \n Allow\n \n MP2\n \n even if one of the lines is not drawn.\n \n
\n\n State\n \n one\n \n assumption of the kinetic model of an ideal gas.\n
\n\n [1]\n
\n\n particles can be considered points «without dimensions»\n \n ✓\n \n
\n\n no intermolecular forces/no forces between particles «except during collisions»\n \n ✓\n \n
\n\n the volume of a particle is negligible compared to volume of gas\n \n ✓\n \n
\n\n collisions between particles are elastic\n \n ✓\n \n
\n\n time between particle collisions are greater than time of collision\n \n ✓\n \n
\n\n no intermolecular PE/no PE between particles\n \n ✓\n \n
\n\n
\n\n \n Accept reference to atoms/molecules for “particle”\n \n
\n\n A glass block has a refractive index in air of\n \n n\n \n \n g\n \n . The glass block is placed in two different liquids: liquid X with a refractive index of\n \n n\n \n \n X\n \n and liquid Y with a refractive index of\n \n n\n \n \n Y\n \n .\n
\n\n In liquid X\n \n and in liquid Y\n \n What is\n \n ?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n In an experiment to determine the speed of sound in air, a tube that is open at the top is filled with water and a vibrating tuning fork is held over the tube as the water is released through a valve.\n
\n\n An increase in intensity in the sound is heard for the first time when the air column length is\n \n \n \n . The next increase is heard when the air column length is\n \n \n \n .\n
\n\n \n
\n Which expressions are approximately correct for the wavelength of the sound?\n
\n\n I. 4\n \n \n \n
\n\n II. 4\n \n \n \n
\n\n III.\n \n \n \n \n \n
\n\n A. I and II\n
\n\n B. I and III\n
\n\n C. II and III\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n B\n
\n\n The question was well answered by students.\n
\n\n The separation of adjacent slits is\n \n d\n \n . Show that for the second-order diffraction maximum\n \n .\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n \n
\n Do\n \n not\n \n award\n \n ECF\n \n from(a)(ii).\n \n
\n Calculate the angular impulse delivered to the flywheel during the acceleration.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «N m s» ✓\n
\n\n Calculate the angular impulse delivered to the flywheel during the acceleration.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «N m s» ✓\n
\n\n The water is heated. Explain why the quantity of air in the storage tank decreases.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «constant\n \n p\n \n and\n \n V\n \n imply»\n \n nT\n \n = const ✓\n
\n\n \n T\n \n increases hence\n \n n\n \n decreases ✓\n
\n\n
\n \n \n ALTERNATIVE 2\n \n \n
\n «constant\n \n p\n \n and\n \n n\n \n imply»\n \n V\n \n is proportional to\n \n T\n \n / air expands as it is heated ✓\n
\n\n «original» air occupies a greater volume\n \n OR\n \n some air leaves through opening ✓\n
\n\n
\n\n \n \n MP2\n \n in\n \n ALT 2\n \n must come from expansion of air, not from expansion of water.\n \n
\n\n \n Award\n \n [0]\n \n for an answer based on expansion of water.\n \n
\n\n \n Award\n \n [1]\n \n \n max\n \n for an answer based on convection currents.\n \n
\n\n It was surprising to see a large number of answers based on the expansion of water, as the stem of the question clearly states that the level of water remains constant. Most successful candidates scored by quoting\n \n pV\n \n constant so concluding with the inverse relationship of n and\n \n T\n \n , others also managed to score by explaining that the volume of air increases and therefore must go out through the opening. Answers based on convection currents were given partial credit.\n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n Pluto rotates about an axis through its centre. Its rotation is in the opposite sense to that of the Earth, i.e. from east to west.\n
\n\n Explain the advantage of an object launching from the equator of Pluto and travelling to the west.\n
\n\n [3]\n
\n\n Object at equator has the maximum linear/tangential speed possible ✓\n
\n\n It therefore has maximum kinetic energy before takeoff (and this is not required from the fuel) ✓\n
\n\n Idea that the object is already moving in direction of planet before takeoff ✓\n
\n\n Explain why the electric potential decreases from A to B.\n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n
\n \n \n work done on moving a positive test charge in any outward direction is negative\n \n \n ✓\n
\n \n \n potential difference is proportional to this work\n \n \n «\n \n \n so\n \n \n \n \n \n decreases from A to B\n \n \n »\n \n \n ✓\n \n
\n
\n\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n \n potential gradient is directed opposite to the field so inwards\n \n \n ✓\n
\n \n \n the gradient indicates the direction of increase of\n \n \n \n \n \n «\n \n \n hence\n \n \n \n \n \n increases towards the centre/decreases from A to B\n \n \n »\n \n \n ✓\n \n
\n
\n\n \n \n \n ALTERNATIVE 3\n \n \n
\n \n \n \n \n \n so as\n \n \n \n \n \n increases\n \n \n \n \n \n decreases\n \n \n ✓\n
\n \n \n \n \n \n is positive as\n \n \n \n \n \n is positive\n \n \n ✓\n \n
\n \n \n
\n\n \n \n \n ALTERNATIVE 4\n \n \n
\n \n \n the work done per unit charge in bringing a positive charge from infinity\n \n \n ✓\n
\n \n \n to point B is less than point A\n \n \n ✓\n \n
\n The majority who answered in terms of potential gained one mark. Often the answers were in terms of work done rather than work done per unit charge or missed the fact that the potential is positive.\n
\n\n The quantity of trapped gas is 53.2 mol. Calculate the thermal energy removed from the gas during process CA.\n
\n\n [2]\n
\n\n «W = 0 so» Q = ΔU ✓\n
\n\n «ΔU =\n \n × 53.2 × R × (351 – 27) so » ΔU = 2.15 × 10\n \n 5\n \n «J» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n A bicycle of mass\n \n comes to rest from speed\n \n using the back brake. The brake has a specific heat capacity of\n \n and a mass\n \n . Half of the kinetic energy is absorbed by the brake.\n
\n\n What is the change in temperature of the brake?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n \n Describe the subsequent motion of the electron.\n \n
\n\n [3]\n
\n\n \n the electron moves away from the point charge/to the right «along the line joining them» ✔\n
\n decreasing acceleration ✔\n
\n increasing speed ✔\n \n
\n \n \n NOTE: Allow ECF from MP1 if a candidate mistakenly evaluates the force as attractive so concludes that the acceleration will increase\n \n \n
\n\n State the value of the maximum distance between the stars that can be measured in any reference frame.\n
\n\n [1]\n
\n\n 4.8 «light years» ✓\n
\n\n Determine the force exerted by the spring on the sphere when the sphere is at rest.\n
\n\n [2]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n \n \n \n \n \n ✓\n
\n\n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n Accept use of\n \n leading to\n \n \n \n
\n\n Continuing from b, most candidates scored full marks.\n
\n\n The player’s foot is in contact with the ball for 55 ms. Calculate the average force that acts on the ball due to the football player.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n Allow\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow\n \n ECF\n \n for\n \n MP2\n \n if 19 sin22\n \n OR\n \n 19 cos22 used.\n \n
\n\n Determine, in days, the half-life of\n \n .\n
\n\n [2]\n
\n\n Slope =«−»\n \n «s\n \n −1\n \n » ✓\n
\n\n \n «\n \n » 3.2 «days» ✓\n
\n\n Suggest\n \n two\n \n changes to the system that will make the geophone more sensitive.\n
\n\n [4]\n
\n\n Any two suggestions from:\n
\n\n Increase number of turns in coil ✓\n
\n Because more flux cutting per cycle ✓\n
\n Increase field strength of magnet ✓\n
\n So that there are more field lines ✓\n
\n Change mass-spring system so that time period decreases ✓\n
\n So magnet will be moving faster for given amplitude of movement ✓\n
\n Sketch, on the\n \n pV\n \n diagram, the remaining two processes BC and CA that the gas undergoes.\n
\n\n [2]\n
\n\n concave curved line from B to locate C with a higher pressure than A ✓\n
\n\n vertical line joining C to A ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n i.e.,\n \n award [1]\n \n for first process locating C at a lower pressure than A, then vertical line to A.\n \n
\n\n \n Arrows on the processes are not needed.\n \n
\n\n \n Point C need not be labelled.\n \n
\n\n \n
\n Calculate, in MeV, the energy released in this decay.\n
\n\n [2]\n
\n\n (\n \n m\n \n \n polonium\n \n −\n \n m\n \n \n lead\n \n −\n \n m\n \n α\n \n \n )\n \n c\n \n \n 2\n \n \n \n OR\n \n \n (209.93676 − 205.92945 − 4.00151)\n
\n\n \n \n OR\n \n \n
\n\n mass difference = 5.8 × 10\n \n −3\n \n ✓\n
\n\n
\n\n conversion to MeV using 931.5 to give 5.4 «MeV» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n .\n \n
\n\n \n Award\n \n [2]\n \n for a\n \n BCA\n \n .\n \n
\n\n \n Award\n \n [1]\n \n for 8.6 x 10\n \n −13\n \n J.\n \n
\n\n Generally, well answered. There were quite a few who fell into the trap of multiplying by an unnecessary c\n \n 2\n \n as they were not sure of the significance of the unit of u.\n
\n\n \n state and explain whether the second law of thermodynamics is violated.\n \n
\n\n [2]\n
\n\n \n not violated ✔\n \n
\n\n \n the entropy of the surroundings must have increased\n
\n \n \n OR\n \n \n
\n the overall entropy of the system and the surroundings is the same or increased ✔\n \n
\n Calculate the internal resistance of the photovoltaic cell for the maximum intensity condition using the model for the cell.\n
\n\n
\n\n [3]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n pd dropped across cell\n \n ✓\n
\n internal resistance\n \n ✓\n
\n\n \n \n ✓\n \n
\n\n \n \n
\n ALTERNATIVE 2\n \n \n
\n \n \n so\n \n \n ✓\n \n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Alternative solutions are possible\n \n
\n \n Award\n \n [3]\n \n marks for a bald correct answer\n \n
\n\n Describe\n \n one\n \n other method by which significant amounts of energy can be transferred from the pipe to the surroundings.\n
\n\n [2]\n
\n\n convection «is likely to be a significant loss» ✓\n
\n\n
\n «due to reduction in density of air near pipe surface» hot air rises «and is replaced by cooler air from elsewhere»\n
\n \n \n OR\n \n \n
\n\n «due to» conduction «of heat or thermal energy» from pipe to air ✓\n
\n\n A few candidates recognized that convection was the third source of heat loss, although few managed to describe the mechanism of convection properly for MP2. Some candidates did not read the question carefully and instead wrote about methods to increase the rate of heat loss (such as removing more insulation or decreasing the temperature of the environment).\n
\n\n Calculate the work done during the compression.\n
\n\n [1]\n
\n\n \n «\n \n \n –\n \n \n »\n \n \n \n \n \n «\n \n »\n \n \n ✓\n \n
\n\n
\n\n State and explain the magnitude of the resultant gravitational field strength at O.\n
\n\n [2]\n
\n\n g = 0 ✓\n
\n\n As g «=\n \n which» is the gradient of the graph\n
\n\n \n \n OR\n \n \n
\n As the force of attraction/field strength of P and M are equal ✓\n
\n Which lists one scalar and two vector quantities?\n
\n\n A. Mass, momentum, potential difference\n
\n\n B. Mass, power, velocity\n
\n\n C. Power, intensity, velocity\n
\n\n D. Power, momentum, velocity\n
\n\n [1]\n
\n\n D\n
\n\n When the spheres move outward, the angular speed decreases from 20 rad s\n \n −1\n \n to 12 rad s\n \n −1\n \n . Calculate the percentage change in rotational kinetic energy that occurs when the spheres move outward.\n
\n\n [2]\n
\n\n \n «E\n \n \n k\n \n =»\n \n \n Lω\n \n \n 1\n \n \n =\n \n Lω\n \n 2\n \n \n ✓\n
\n\n \n \n OR\n \n \n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n «\n \n L\n \n is constant so»\n \n E\n \n \n k\n \n is proportional to\n \n ω\n \n ✓\n
\n\n 40 % «energy loss» ✓\n
\n\n
\n\n \n \n MP1\n \n is for understanding that angular momentum is constant so change in rotational kinetic energy is proportional to change in angular velocity\n \n
\n\n \n \n Award [0]\n \n if E = 0.5 I ω\n \n 2\n \n is used with the same I value for both values of E\n \n
\n\n \n Award\n \n [2]\n \n for\n \n BCA\n \n \n
\n\n Calculate, in m, the distance to star X.\n
\n\n [1]\n
\n\n «distance =\n \n × 3.26 × 9.46 × 10\n \n 15\n \n »\n
\n\n 1.6 × 10\n \n 18\n \n «m» ✓\n
\n\n Show that the magnitude of the resultant electric field at P is 3 MN C\n \n −1\n \n
\n\n [2]\n
\n\n «electric field at P from one charge is\n \n »\n \n
\n\n \n \n OR\n \n \n
\n\n \n «NC\n \n −1\n \n » ✓\n
\n\n
\n « net field is »\n \n «NC\n \n −1\n \n » ✓\n
\n Outline one reason why this model of a dancer is unrealistic.\n
\n\n [1]\n
\n\n one example specified\n \n eg\n \n friction, air resistance, mass distribution not modelled ✓\n
\n\n
\n\n \n \n Award [1]\n \n for any reasonable physical parameter that is not consistent with the model\n \n
\n\n \n Determine, using the first law of thermodynamics, the total thermal energy transferred to the building during the processes C→A and A→B.\n \n
\n\n [3]\n
\n\n \n for CA Δ\n \n U\n \n \n =\n \n 0 so\n \n Q = W\n \n = −440 «\n \n J\n \n » ✔\n
\n \n
\n \n for AB\n \n W\n \n = 0 so\n \n Q\n \n =\n \n Δ\n \n U =\n \n −\n \n 375 «J» ✔\n
\n \n
\n \n 815 «J» transferred to the building ✔\n \n
\n\n \n \n \n Must use the first law of thermodynamics for MP1 and MP2.\n \n \n \n
\n\n The main problem here was deciding whether each Q was positive or negative. But the question was quite well answered.\n
\n\n A standing wave is formed on a rope. The distance between the first and fifth antinode on the standing wave is 60 cm. What is the wavelength of the wave?\n
\n\n A. 12 cm\n
\n\n B. 15 cm\n
\n\n C. 24 cm\n
\n\n D. 30 cm\n
\n\n [1]\n
\n\n D\n
\n\n Option D was the most common (correct) answer, however answers A and B proved to be significant distractors. This would be a useful practice question when reviewing standing waves, nodes/antinodes and wavelengths.\n
\n\n Estimate the escape speed of the spacecraft from the planet–star system.\n
\n\n [2]\n
\n\n use of\n \n v\n \n \n esc\n \n =\n \n \n ✓\n \n
\n\n \n v =\n \n 9.91 × 10\n \n 4\n \n «m s\n \n −1\n \n »\n \n ✓\n \n
\n\n
\n\n
\n\n Calculate the mass of the oil that remains unfrozen after\n \n minutes.\n
\n\n [2]\n
\n\n \n mass of frozen oil\n \n \n \n ✓\n \n
\n\n \n unfrozen mass\n \n \n \n ✓\n \n
\n\n The top of the wall is 2.4 m above the ground. Deduce whether the ball will hit the wall.\n
\n\n [3]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n ball does not hit wall\n \n \n OR\n \n \n 2.5 «m» > 2.4 «m»\n \n ✓\n \n
\n\n \n
\n Allow\n \n ECF\n \n from (b)(i) and from\n \n MP1\n \n \n
\n \n Allow g = 10 m s\n \n −2\n \n \n
\n\n An engineer needs to move a space probe of mass 3600 kg from Ganymede to Callisto. Calculate the energy required to move the probe from the orbital radius of Ganymede to the orbital radius of Callisto. Ignore the mass of the moons in your calculation.\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n « multiplies by 3600 kg to get » 1.9 × 10\n \n 11\n \n «J»\n \n ✓\n \n
\n\n \n
\n Award\n \n [2]\n \n marks if factor of ½ used, taking into account orbital kinetic energies, leading to a final answer of 9.4 x 10\n \n 10\n \n «J».\n \n
\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n \n Award\n \n [2] marks\n \n for a bald correct answer.\n \n
\n\n \n A satellite travels around the Earth in a circular orbit. What is true about the forces acting in this situation?\n \n
\n\n \n A. The resultant force is the same direction as the satellite’s acceleration.\n
\n \n
\n \n B. The gravitational force acting on the satellite is negligible.\n
\n \n
\n \n C. There is no resultant force on the satellite relative to the Earth.\n
\n \n
\n \n D. The satellite does not exert any force on the Earth.\n \n
\n\n [1]\n
\n\n A\n
\n\n Outline how a standing wave is produced on the string.\n
\n\n [2]\n
\n\n «travelling» wave moves along the length of the string and reflects «at fixed end»\n \n ✓\n \n
\n\n superposition/interference of incident and reflected waves\n \n ✓\n \n
\n\n the superposition of the reflections is reinforced only for certain wavelengths\n \n ✓\n \n
\n\n Draw on the axes the variation of gravitational potential between O and M.\n
\n\n [1]\n
\n\n Line always negative, of suitable shape and end point below −8 and above −20 unless awarding\n \n \n ECF\n \n \n from\n \n \n b(iv)\n \n \n ✓\n
\n\n \n
\n \n During its evolution, the Sun is likely to be a red giant of surface temperature 3000 K and luminosity 10\n \n 4\n \n L\n \n \n \n ☉\n \n . Later it is likely to be a white dwarf of surface temperature 10 000 K and luminosity 10-4 L\n \n \n \n ☉\n \n . Calculate the\n \n \n \n .\n \n
\n\n [2]\n
\n\n \n
\n Calculating the ratio of the radius of a white dwarf to a red giant star was done quite well by most candidates. However quite a few candidates made POT errors or forgot to take the final square root.\n
\n\n using a light source with a smaller wavelength.\n
\n\n [1]\n
\n\n gradient smaller\n \n ✓\n \n
\n\n Outline how this standing wave pattern of melted spots is formed.\n
\n\n [2]\n
\n\n standing waves form «in the oven» by superposition / constructive interference ✓\n
\n\n energy transfer is greatest at the antinodes «of the standing wave pattern» ✓\n
\n\n Outline how this standing wave pattern of melted spots is formed.\n
\n\n [2]\n
\n\n standing waves form «in the oven» by superposition / constructive interference ✓\n
\n\n energy transfer is greatest at the antinodes «of the standing wave pattern» ✓\n
\n\n A travelling wave on the surface of a lake has wavelength\n \n . Two points along the wave oscillate with the phase difference of\n \n . What is the smallest possible distance between these two points?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n B\n
\n\n Which statement is correct about the entropy of a non-isolated system?\n
\n\n
\n A. It always increases\n
\n B. It always decreases\n
\n\n C. It can only increase if the entropy of the surroundings decreases\n
\n\n D. It can only decrease if the entropy of the surroundings increases\n
\n\n [1]\n
\n\n D\n
\n\n State what is meant by the Doppler effect.\n
\n\n [2]\n
\n\n the change in the observed frequency ✓\n
\n\n when there is relative motion between the source and the observer ✓\n
\n\n
\n\n \n Do not award\n \n MP1\n \n if they refer to wavelength.\n \n
\n\n Determine the minimum area of the solar heating panel required to increase the temperature of all the water in the tank to 30°C during a time of 1.0 hour.\n
\n\n [3]\n
\n\n energy required = 250 × 4200 × (30 − 15) ✓\n
\n\n energy available = 0.30 × 680 ×\n \n t\n \n ×\n \n A\n \n ✓\n
\n\n \n A\n \n = «\n \n » 21 «m\n \n 2\n \n »\n \n \n OR\n \n \n 22 «m\n \n 2\n \n » ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n and\n \n MP2\n \n .\n \n
\n\n \n Accept the correct use of 0.30 in either\n \n MP1\n \n or\n \n MP2\n \n .\n \n
\n\n Most candidates had a good attempt at this but there were often slight slips. Some missed the efficiency of the process. Some included the albedo of the roof tiles. Some thought that the temperature rise needed to have 273 added to convert to kelvin. However, sometimes scoring through ECF (error carried forward), the average mark was around 2 marks.\n
\n\n After passing through the circular hole the electrons strike a fluorescent screen.\n
\n\n Predict whether an apparatus such as this can demonstrate that moving electrons have wave properties.\n
\n\n [4]\n
\n\n idea that de Broglie wavelength and hole size must be similar ✓\n
\n\n Use of\n \n ✓\n
\n\n Leading to\n \n around 5 x 10\n \n −11\n \n m (which is unrealistic for a practical situation) ✓\n
\n\n It would not be possible to construct this hole\n
\n \n OR\n \n
\n hole must be smaller than an atom so impossible ✓\n
\n \n does not support the wave nature of light.\n \n
\n\n [2]\n
\n\n \n «low intensity light would» transfer energy to the electron at a low rate/slowly ✔\n
\n time would be required for the electron «to absorb the required energy» to escape/be emitted ✔\n
\n \n
\n \n \n NOTE: OWTTE\n \n \n
\n\n When monochromatic light is incident on a single slit a diffraction pattern forms on a screen. The width of the slit is decreased.\n
\n\n What are the changes in the width and in the intensity of the central maximum of the diffraction pattern?\n
\n\n
\n \n
\n [1]\n
\n\n B\n
\n\n The student then makes the ramp horizontal and applies a constant horizontal force to the box. The force is just large enough to start the box moving. The force continues to be applied after the box begins to move.\n
\n\n \n
\n Explain, with reference to the frictional force acting, why the box accelerates once it has started to move.\n
\n\n [3]\n
\n\n static coefficient of friction > dynamic/kinetic coefficient of friction / μ\n \n s\n \n > μ\n \n k\n \n ✓\n
\n\n «therefore» force of dynamic/kinetic friction will be less than the force of static friction ✓\n
\n\n
\n there will be a net / unbalanced forward force once in motion «which results in acceleration»\n
\n \n \n OR\n \n \n
\n\n reference to net F = ma ✓\n
\n\n This was an \"explain\" question, so examiners were looking for a clear line of discussion starting with a comparison of the coefficients of friction, leading to a comparison of the relative magnitudes of the forces of friction and ultimately the rise of a net force leading to an acceleration. Many candidates recognized that this was a question about the comparison between static and kinetic/dynamic friction but did not clearly specify which they were referring to in their responses. Some candidates clearly did not read the stem carefully as they referred to the mass being on an incline.\n
\n\n Calculate the energy lost during the collision.\n
\n\n [2]\n
\n\n \n × 0.200 × 12.0\n \n 2\n \n −\n \n (0.252) × 5.71\n \n 2\n \n ✓\n
\n\n 10.3 J ✓\n
\n\n
\n\n \n \n Award [1]\n \n for answer 11.5\n \n J\n \n that neglects moment of inertia of particle but do not penalize this omission in\n \n (d)(i)\n \n .\n \n
\n\n Show that the volume at C is 3.33 × 10\n \n −2\n \n m\n \n 3\n \n .\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n Use of adiabatic formula «\n \n »\n \n ✓\n
\n\n \n × 2.00 × 10\n \n −3\n \n «= 3.333 × 10\n \n −2\n \n m\n \n 3\n \n » ✓\n
\n\n
\n\n \n For\n \n MP2\n \n , working or answer to at least 4 SF must be seen.\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n p\n \n \n A\n \n \n V\n \n \n A\n \n =\n \n p\n \n \n B\n \n \n V\n \n \n B\n \n ✓\n
\n\n \n ✓\n
\n\n
\n\n \n \n ALTERNATIVE 3\n \n \n
\n\n \n V\n \n \n C\n \n =\n \n V\n \n \n B\n \n \n \n AND\n \n \n \n n\n \n = 0.2 mol ✓\n
\n\n \n V\n \n \n C\n \n = (0.2 × 8.31 × 602) / 4 × 10\n \n 4\n \n ✓\n
\n\n When removed from a nuclear reactor, used nuclear fuel rods are often stored for several years in a tank of liquid.\n
\n\n Three possible reasons for this are\n
\n\n I. to shield workers from radiation emitted from the fuel rods\n
\n II. to dissolve the unused fuel from the rods\n
\n III. to cool the rods\n
\n Which statements are correct?\n
\n\n
\n A. I and II only\n
\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I II and III\n
\n\n [1]\n
\n\n B\n
\n\n Outline why the entropy of the gas remains constant during changes BC and DA.\n
\n\n [1]\n
\n\n From\n \n , the change in entropy is zero when\n \n ✓\n
\n\n Show that the tension\n \n T\n \n in the string is\n \n \n \n
\n\n [1]\n
\n\n use of\n \n T =\n \n \n \n \n \n MR\n \n \n \n \n to find\n \n T\n \n =\n \n \n \n \n MR ×\n \n \n \n \n ✔\n
\n\n «cancelling to show final answer»\n
\n\n This simple system of a solid cylinder rotating about a fixed axle and a block hanging on the rope accelerating proved to be rather difficult for many candidates. Only the best candidates were able to solve this problem, by writing two separate equations, and then solving to establish the acceleration of the system. The use of energy conservation was not a common technique attempted by students. As this is a “show that” question, candidates were asked to show that the angular acceleration is equal to g/(3R). Quite a high number of candidates successfully used the equations of motion and a similar number used the moment of inertia of the block around the axle. In ii), well-prepared candidates used the angular acceleration of the cylinder from i) and the tension expression to arrive at the given Mg/6.\n
\n\n Configuration B has 120 microstates. Calculate the entropy difference between configurations B and A. State the answer in terms of\n \n .\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n the angular deceleration of the rod.\n
\n\n [1]\n
\n\n \n =\n \n = 0.603 rads\n \n −2\n \n ✓\n
\n\n
\n\n \n Accept negative values.\n \n
\n\n The scale diagram shows the weight\n \n W\n \n of the mass at an instant when the rod is horizontal.\n
\n\n Draw, on the scale diagram, an arrow to represent the force exerted on the mass by the rod.\n
\n\n \n
\n [2]\n
\n\n horizontal component of any length to the left ✓\n
\n\n vertical component two squares long upwards ✓\n
\n\n E.g.\n
\n\n \n
\n
\n\n \n Ignore point of application.\n \n
\n\n \n Award\n \n [1]\n \n \n max\n \n if arrowhead not present.\n \n
\n\n Most just added the horizontal component. Not many centrifugal forces, but still a few. Very few were able to score both marks, so this question proved to be challenging for the candidates.\n
\n\n Three mechanisms that affect the composition of the atmosphere of the Earth are:\n
\n\n I. Loss of forests that would otherwise store carbon dioxide – CO\n \n 2\n \n
\n II. Release of methane – CH\n \n 4\n \n by the digestive system of grazing animals\n
\n III. Increase of nitrous oxide – N\n \n 2\n \n O due to extensive use of fertilizer\n
\n Which of these statements describe a process that contributes to global warming?\n
\n\n A. I and II only\n
\n\n B. I and III only\n
\n\n C. II and III only\n
\n\n D. I, II and III\n
\n\n [1]\n
\n\n D\n
\n\n This question was well answered by candidates, although option A was a frequent distractor suggesting candidates may be less clear about the role of nitrous oxide in global warming.\n
\n\n Deduce the value of\n \n g\n \n and its absolute uncertainty for this experiment.\n
\n\n [2]\n
\n\n \n g\n \n = 9.996 «m s\n \n −2\n \n »\n \n \n OR\n \n \n Δ\n \n g =\n \n 4.20 «m s\n \n −2\n \n » ✔\n
\n\n \n g\n \n = (10 ± 4) «m s\n \n −2\n \n »\n
\n\n \n \n OR\n \n \n
\n\n \n g\n \n = (10.0 ± 4.2) «m s\n \n −2\n \n » ✔\n
\n\n \n Award\n \n [1]\n \n max for not proper significant digits or decimals use, such as: 9.996±4.178 or 10±4.2 or 10.0±4 or 10.0±4.18« m s\n \n −2\n \n »\n \n .\n
\n\n Many average candidates did not use the correct number of significant figures and wrote the answers inappropriately. Only the best candidates rounded out and wrote the proper answer of 10±4 ms\n \n −2\n \n . Some candidates did not propagate uncertainties and only compared the average calculated value with the known value 9.81 ms\n \n −2\n \n .\n
\n\n A mass at the end of a string is moving in a horizontal circle at constant speed. The string makes an angle\n \n θ\n \n to the vertical.\n
\n\n \n
\n What is the magnitude of the acceleration of the mass?\n
\n\n
\n A.\n \n g\n \n
\n B.\n \n g\n \n sin\n \n θ\n \n
\n\n C.\n \n g\n \n cos\n \n θ\n \n
\n\n D.\n \n g\n \n tan\n \n θ\n \n
\n\n [1]\n
\n\n D\n
\n\n The Compton effect can be explained using\n
\n\n
\n A. conservation of momentum\n
\n B. kinematic equations applied in two dimensions\n
\n\n C. the concept of a photon\n
\n\n D. the wave theory of light\n
\n\n [1]\n
\n\n A\n
\n\n Monochromatic electromagnetic radiation ejects photoelectrons from a metal surface. The minimum frequency for which this is possible is\n \n .\n
\n\n When radiation of frequency 2\n \n is incident on the surface, the kinetic energy of the photoelectrons is\n \n K\n \n .\n
\n\n What is the kinetic energy of the photoelectrons when the frequency of the radiation is 4\n \n ?\n
\n\n
\n A.\n \n K\n \n
\n B. 2\n \n K\n \n
\n\n C. 3\n \n K\n \n
\n\n D. 4\n \n K\n \n
\n\n [1]\n
\n\n C\n
\n\n A difficult but well discriminating question. The relationship between the KE of the photoelectrons and photon frequency is\n \n not\n \n directly proportional which eliminates alternative B (the most popular but incorrect answer). A sketch graph of KE against frequency helps to identify the correct answer, e.g. by considering the increase in KE over equal frequency intervals of length\n \n f\n \n .\n
\n\n \n When\n \n d\n \n = 0.200 mm,\n \n s\n \n = 0.9 mm and\n \n D\n \n = 280 mm, determine the percentage uncertainty in the wavelength.\n \n
\n\n [2]\n
\n\n Evidence of\n \n \n \n \n used\n \n ✔\n \n \n \n
\n \n
\n \n \n «add fractional/% uncertainties»\n
\n \n \n
\n \n \n obtains 11 % (or 0.11)\n \n \n OR\n \n \n 10 % (or 0.1) ✔\n \n \n
\n\n A very easy question about percentage uncertainty which most candidates got completely correct. Many candidates gave the uncertainty to 4 significant figures or more. The process used to obtain the final answer was often difficult to follow.\n
\n\n \n Explain, using your answer to (d)(i) and with reference to the kinetic model, why this sample of helium can be assumed to be an ideal gas.\n \n
\n\n [2]\n
\n\n \n «For an ideal gas» the size of the particles is small compared to the distance between them/size of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» the volume of the particles is negligible/the volume of the particles is small compared to the volume of the container/gas\n
\n \n
\n \n \n \n OR\n \n \n
\n \n
\n \n «For an ideal gas» particles are assumed to be point objects ✔\n
\n \n
\n \n calculation/ratio/result in (d)(i) shows that volume of helium atoms is negligible compared to/much smaller than volume of helium gas/container «hence assumption is justified» ✔\n \n
\n\n In general this was poorly answered at SL. Many other non-related gas properties given such as no / negligible intermolecular forces, low pressure, high temperature. Some candidates interpreted the ratio as meaning it is a low density gas. At HL candidates seemed more able to focus on the key part feature of the question, which was the nature of the volumes involved. Examiners were looking for an assumption of the kinetic theory related to the volume of the atoms/gas and then a link to the ratio calculated in ci). The command terms were slightly different at SL and HL, giving slightly more guidance at SL.\n
\n\n \n Identify the fundamental units of\n \n \n .\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n Accept\n \n \n \n
\n\n \n \n
\n\n Although the question was specifically about the fundamental units, several candidates lost the mark by answering Pa m.\n
\n\n Suggest, for the change A ⇒ B, whether the entropy of the gas is increasing, decreasing or constant.\n
\n\n [2]\n
\n\n Increasing ✓\n
\n\n because thermal energy/heat is being provided to the gas « and temperature is constant,\n \n ✓\n
\n\n Estimate the power input to the heating element. State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n energy required for milk entering in 1 s = mass x specific heat x 73 ✓\n
\n\n 16 kW\n \n \n OR\n \n \n 16000 W ✓\n
\n\n
\n\n \n \n MP1\n \n is for substitution into mcΔT regardless of power of ten.\n \n
\n\n \n Allow any correct unit of power (such as\n \n J s\n \n -1\n \n \n OR\n \n kJ s\n \n -1\n \n \n ) if paired with an answer to the correct power of 10 for\n \n MP2\n \n .\n \n
\n\n Most candidates recognized that this was a specific heat question and set up a proper calculation, but many struggled to match their answer to an appropriate unit. A common mistake was to leave the answer in some form of an energy unit and others did not match the power of ten of the unit to their answer (e.g. 16 W).\n
\n\n Suggest why AC is the adiabatic part of the cycle.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «considering expansions from A» an adiabatic process will reduce/change temperature ✓\n
\n\n and so curve AC must be the steeper ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n temperature drop occurs for BC ✓\n
\n\n therefore CA must increase temperature «via adiabatic process». ✓\n
\n\n Every neutron-induced fission reaction of uranium-235 releases an energy of about 200 MeV. A nuclear power station transfers an energy of about 2.4 GJ per second.\n
\n\n Determine the mass of uranium-235 that undergoes fission in one day in this power station.\n
\n\n [3]\n
\n\n Fissions per day\n \n «\n \n » ✓\n
\n\n Mass of uranium\n \n ✓\n
\n\n 2.5 «kg» ✓\n
\n\n Calculate:\n
\n\n
\n\n \n ✓\n
\n\n K m\n \n −1\n \n ✓\n
\n\n A black-body radiator emits a peak wavelength of\n \n and a maximum power of\n \n . The peak wavelength emitted by a second black-body radiator with the same surface area is\n \n . What is the total power of the second black-body radiator?\n
\n\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n A\n
\n\n The designers state that the energy transferred by the resistor every second is 15 J.\n
\n\n Calculate the current in the resistor.\n
\n\n [1]\n
\n\n \n I\n \n = «\n \n =» 1.9 «A» ✓\n
\n\n Explain why\n \n q\n \n will perform simple harmonic oscillations when it is released.\n
\n\n [2]\n
\n\n force «on\n \n q\n \n » is proportional to the displacement ✓\n
\n\n and opposite to the displacement / directed towards equilibrium ✓\n
\n\n Outline the cause of the electron emission for radiation A.\n
\n\n [1]\n
\n\n photon transfers «all» energy to electron\n \n ✓\n \n
\n\n Draw the electric field lines due to the charged plates.\n
\n\n [2]\n
\n\n equally spaced arrows «by eye» all pointing down ✓\n
\n\n edge effects also shown with arrows ✓\n
\n\n \n An electron enters a uniform electric field of strength\n \n E\n \n with a velocity\n \n v\n \n . The direction of\n \n v\n \n is not parallel to\n \n E\n \n . What is the path of the electron after entering the field?\n \n
\n\n \n A. Circular\n
\n \n
\n \n B. Parabolic\n
\n \n
\n \n C. Parallel to\n \n E\n \n
\n \n
\n \n D. Parallel to\n \n v\n \n \n
\n\n [1]\n
\n\n B\n
\n\n Outline\n \n two\n \n differences between the momentum of the box and the momentum of the load at the same instant.\n
\n\n [2]\n
\n\n direction of motion is different /\n \n \n OWTTE\n \n \n ✓\n
\n\n \n mv\n \n / magnitude of momentum is different «even though\n \n v\n \n the same» ✓\n
\n\n Many students recognized the vector nature of momentum implied in the question, although some focused on the forces acting on each object rather than discussing the momentum.\n
\n\n Show that the\n \n is about 80.\n
\n\n [2]\n
\n\n \n \n \n AND\n \n \n \n \n \n seen\n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n For\n \n MP1\n \n , potentials can be seen individually or as a ratio.\n \n
\n Determine the force on Q at the instant it is released.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n «N» ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n marks for a bald correct answer.\n \n
\n\n \n Allow symbolic k in substitutions for\n \n MP1\n \n .\n \n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from incorrect or not squared distance.\n \n
\n\n Determine the maximum kinetic energy\n \n of the cylinder.\n
\n\n [2]\n
\n\n \n «\n \n \n \n is a maximum when\n \n hence\n \n \n »\n \n \n \n ✓\n \n
\n\n
\n \n \n ✓\n \n
\n A straightforward calculation with the most common mistake being missing the squared on the omega.\n
\n\n Calculate the number of gas particles in the cylinder.\n
\n\n [2]\n
\n\n Correct conversion of T «T = 310 K» seen ✓\n
\n\n « use of =\n \n to get » 2.3 × 10\n \n 23\n \n ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n i.e., T in Celsius (Result is 2.7 x 10\n \n 24\n \n )\n \n
\n\n \n Allow use of n, R and N\n \n A\n \n \n
\n\n a) This was well answered with the majority converting to K. Quite a few found the number of moles but did not then convert to molecules.\n
\n\n bi) Well answered. It was pleasing to see how many recognised the need to state that the mass/number of molecules stayed the same as well as stating that the volume increased. At SL this recognition was less common so only 1 mark was often awarded.\n
\n\n bii) This was less successfully answered. A surprising number of candidates said that the internal energy of an ideal gas increases during an isothermal expansion. Many recognised that constant temp meant constant KE but then went on to state that the PE must increase and so the internal energy would increase.\n
\n
\n
\n Explain why the work done by the gas during the isothermal expansion AB is less than the work done on the gas during the adiabatic compression BC.\n
\n\n [1]\n
\n\n area under curve AB is less than area under curve BC ✓\n
\n\n
\n\n \n Do\n \n not\n \n allow\n \n ECF\n \n from part\n \n (b)\n \n \n
\n\n Calculate the speed of the combined masses immediately after the collision.\n
\n\n [1]\n
\n\n 0.40 «m s\n \n −1\n \n » ✔\n
\n\n Candidates fell into some broad categories on this question. This was a “show that” question, so there was an expectation of a mathematical argument. Many were able to successfully show that the initial and final kinetic energies were different and connect this to the concept of inelastic collisions. Some candidates tried to connect conservation of momentum unsuccessfully, and some simply wrote an extended response about the nature of inelastic collisions and noted that the bobs stuck together without any calculations. This approach was awarded zero marks.\n
\n\n State the unit for\n \n pV\n \n in fundamental SI units.\n
\n\n [1]\n
\n\n kg m\n \n 2\n \n s\n \n −2\n \n ✓\n
\n\n State the main element that is undergoing nuclear fusion in star C.\n
\n\n [1]\n
\n\n Hydrogen ✓\n
\n\n Calculate the largest fractional uncertainty in\n \n T\n \n for these data.\n
\n\n [2]\n
\n\n \n T\n \n = 0.5 s ✓\n
\n\n «\n \n » 0.2 ✓\n
\n\n Show that the energy dissipated in the loop from\n \n t\n \n = 0 to\n \n t\n \n = 3.5 s is 0.13 J.\n
\n\n [2]\n
\n\n Energy is being dissipated for 0.50 s ✓\n
\n\n
\n \n «\n \n J»\n
\n \n \n OR\n \n \n
\n\n \n «\n \n J» ✓\n
\n\n
\n\n \n Allow\n \n ECF\n \n from\n \n (b)\n \n and\n \n (c)\n \n .\n \n
\n\n \n Watch for candidates who do not justify somehow the use of 0.5 s and just divide by 2 their answer.\n \n
\n\n The gravitational potential due to the mass of M at the surface of P can be assumed to be negligible.\n
\n\n Estimate, using the graph, the gravitational potential at the surface of M due to the mass of M.\n
\n\n [2]\n
\n\n «\n \n =\n \n = 0.75 × 0.27» = 0.20 ✓\n
\n\n \n V\n \n \n M\n \n = «−6.4 × 10\n \n 7\n \n × 0.2 =» «−»1.3 × 10\n \n 7\n \n «J kg\n \n −1\n \n »✓\n
\n\n \n The force acting between two point charges is\n \n \n \n when the separation of the charges is\n \n \n \n . What is the force between the charges when the separation is increased to\n \n ?\n \n
\n\n \n A.\n \n \n
\n\n \n B.\n \n \n
\n\n \n C.\n \n \n
\n\n \n D.\n \n \n
\n\n [1]\n
\n\n C\n
\n\n direction of the net force acting on the loop.\n
\n\n [1]\n
\n\n Repulsive / to the right ✓\n
\n\n The photoelectrons are emitted from a sodium surface. Sodium has a work function of 2.3 eV.\n
\n\n Calculate the wavelength of the radiation incident on the sodium. State an appropriate unit for your answer.\n
\n\n [3]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n \n
\n Must see an appropriate unit to award\n \n MP3.\n \n \n
\n The two slits are replaced by many slits of the same separation. State\n \n one\n \n feature of the intensity pattern that will remain the same and\n \n one\n \n that will change.\n
\n\n Stays the same:\n
\n\n
\n\n Changes:\n
\n\n [2]\n
\n\n Stays the same: Position/location of maxima/distance/separation between maxima «will be the same» /\n \n \n OWTTE\n \n \n ✓\n
\n\n Changes: Intensity/brightness/width/sharpness «of maxima will change»/\n \n \n OWTTE\n \n \n ✓\n
\n\n \n Allow other phrasing for maxima (fringes, spots, etc).\n \n
\n\n A plate performs simple harmonic oscillations with a frequency of 39 Hz and an amplitude of 8.0 cm.\n
\n\n Show that the maximum speed of the oscillating plate is about 20 m s\n \n −1\n \n .\n
\n\n [2]\n
\n\n use of\n \n ✓\n
\n\n maximum speed is\n \n «m s\n \n −1\n \n » ✓\n
\n\n
\n\n \n Award\n \n [2]\n \n for a bald correct answer.\n \n
\n\n The graph shows the variation of magnetic flux\n \n in a coil with time\n \n .\n
\n\n \n
\n What represents the variation with time of the induced emf\n \n across the coil?\n
\n\n \n
\n [1]\n
\n\n A\n
\n\n Candidate selections were divided across the options presented, with option B as the most common (incorrect answer). This suggests that candidates could use more guidance on how to interpret slope on a ɛ vs.\n \n t\n \n graph.\n
\n\n \n In order to find the uncertainty for\n \n \n \n \n \n , a maximum gradient line would be drawn. On the graph, sketch the maximum gradient line for the data.\n \n
\n\n [1]\n
\n\n \n straight line, gradient\n \n g\n \n \n \n \n reater\n \n \n \n than line of best fit, and within the error bars\n \n \n ✓\n \n
\n\n \n \n \n
\n Almost all candidates were able to draw the correct maximum gradient line.\n
\n\n State what will happen to the intensity of the secondary maxima.\n
\n\n [1]\n
\n\n decreases ✓\n
\n\n \n Define\n \n proper length\n \n .\n \n
\n\n [1]\n
\n\n \n the length measured «in a reference frame» where the object is at rest ✔\n
\n \n
\n Proper length is quite well understood. A common mistake is to mention that it is the length measured by a reference frame at rest.\n
\n\n The system rotates from rest and reaches a maximum angular speed of 20 rad s\n \n −1\n \n in a time of 5.0 s. Calculate the angular acceleration of the system.\n
\n\n [1]\n
\n\n «α =\n \n =» 4 «rad s\n \n −2\n \n » ✓\n
\n\n The two slits are replaced by many slits of the same separation. State\n \n one\n \n feature of the intensity pattern that will remain the same and\n \n one\n \n that will change.\n
\n\n Stays the same:\n
\n\n
\n\n Changes:\n
\n\n [2]\n
\n\n Stays the same: Position/location of maxima/distance/separation between maxima «will be the same» /\n \n \n OWTTE\n \n \n ✓\n
\n\n Changes: Intensity/brightness/width/sharpness «of maxima will change»/\n \n \n OWTTE\n \n \n ✓\n
\n\n \n Allow other phrasing for maxima (fringes, spots, etc).\n \n
\n\n Show that the angular acceleration\n \n \n \n of the cylinder is\n \n \n \n
\n\n [3]\n
\n\n equations of motion are:\n \n TR =\n \n \n \n \n \n MR\n \n \n 2\n \n \n \n \n and\n \n \n \n −\n \n T\n \n =\n \n \n \n \n \n \n
\n\n \n \n OR\n \n \n
\n\n \n \n \n \n gR =\n \n \n \n \n \n MR\n \n 2\n \n \n \n \n \n \n +\n \n \n \n \n \n Ra\n \n
\n\n use of\n \n a\n \n =\n \n \n \n \n R\n \n ✔\n
\n\n combine equations to get result ✔\n
\n\n \n Allow energy conservation use.\n \n
\n\n \n This is a show that question, so look for correct working.\n \n
\n\n \n Do not allow direct use of tension from a ii)\n \n
\n\n This simple system of a solid cylinder rotating about a fixed axle and a block hanging on the rope accelerating proved to be rather difficult for many candidates. Only the best candidates were able to solve this problem, by writing two separate equations, and then solving to establish the acceleration of the system. The use of energy conservation was not a common technique attempted by students. As this is a “show that” question, candidates were asked to show that the angular acceleration is equal to g/(3R). Quite a high number of candidates successfully used the equations of motion and a similar number used the moment of inertia of the block around the axle.\n
\n\n Show that the magnitude of the resultant electric field at P is 3 MN C\n \n −1\n \n
\n\n [2]\n
\n\n «electric field at P from one charge is\n \n »\n \n
\n\n \n \n OR\n \n \n
\n\n \n «NC\n \n −1\n \n » ✓\n
\n\n
\n « net field is »\n \n «NC\n \n −1\n \n » ✓\n
\n Determine the critical density of the universe using a Hubble constant value of 73 km s\n \n −1\n \n Mpc\n \n −1\n \n .\n
\n\n [2]\n
\n\n \n H\n \n «=\n \n » = 2.37 × 10\n \n −18\n \n «s\n \n −1\n \n » ✓\n
\n\n \n ρ\n \n c\n \n \n = «\n \n =» 1.0 × 10\n \n −26\n \n «kg m\n \n −3\n \n » ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n \n Allow\n \n ECF\n \n from\n \n MP1\n \n \n
\n\n \n \n Award [1]\n \n for 9.5 × 10\n \n 18\n \n or 9.5 × 10\n \n 12\n \n \n
\n\n Loudspeaker A is switched off. Loudspeaker B moves away from M at a speed of 1.5 m s\n \n −1\n \n while emitting a frequency of 3.0 kHz.\n
\n\n Determine the difference between the frequency detected at M and that emitted by B.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n use of\n \n (+ sign must be seen)\n \n \n OR\n \n \n \n = 2987 «Hz» ✓\n
\n «\n \n » = 13 «Hz» ✓\n
\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n Attempted use of\n \n ≈\n \n
\n
\n « Δf » = 13 «Hz» ✓\n
\n Many candidates were successful in setting up a Doppler calculation and determining the new frequency, although some missed the second step of finding the difference in frequencies.\n
\n\n Just before the collision of the ball with the block,\n
\n\n
\n\n Tension upwards, weight downwards ✓\n
\n Tension is clearly longer than weight ✓\n
\n
\n\n \n Look for:\n \n
\n\n \n
\n The student plots a graph with\n \n L\n \n on the horizontal axis. State the variable that must be plotted on the vertical axis in order to obtain a line of best fit that is straight.\n
\n\n [1]\n
\n\n \n T\n \n \n 2\n \n ✓\n
\n\n Show that the charge on the surface of the sphere is +18 μC.\n
\n\n [1]\n
\n\n \n
\n\n \n \n OR\n \n \n
\n\n \n «μC» ✓\n
\n\n In one throw the coins all land heads upwards. The following throw results in 7 heads and 3 tails. Calculate, in terms of\n \n , the change in entropy between the two throws.\n
\n\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n Show that the maximum velocity of the photoelectrons is\n \n .\n
\n\n [2]\n
\n\n «\n \n » and manipulation to get\n \n \n ✓\n \n
\n\n \n \n \n OR\n \n \n \n \n ✓\n \n
\n\n \n Must see either complete substitution or calculation to at least 3 s.f. for\n \n MP2\n \n \n
\n\n Show that the decay constant of a nuclide is given by −\n \n m\n \n , where\n \n m\n \n is the slope of the graph of ln\n \n A\n \n against\n \n t\n \n .\n
\n\n [1]\n
\n\n Takes ln of both sides of\n \n , leading to\n \n ✓\n
\n\n «hence slope\n \n » ✓\n
\n\n Describe the photoelectric effect.\n
\n\n [2]\n
\n\n electrons are ejected from the surface of a metal\n \n ✓\n \n
\n\n after gaining energy from photons/electromagnetic radiation\n \n ✓\n \n
\n\n there is a minimum «threshold» energy/frequency\n
\n \n \n OR\n \n \n
\n maximum «threshold» wavelength\n \n ✓\n \n
\n A spaceship leaves Earth and travels at a speed of 0.60\n \n c\n \n relative to the Earth to a point P.\n
\n\n P is 3.0 lightyears from Earth.\n
\n\n The spaceship then returns to Earth. Ignore the time taken to reverse the direction of the spaceship.\n
\n\n What is the time taken for the total journey to and from P as measured by an observer in the spaceship?\n
\n\n
\n A. 6.3 years\n
\n B. 5.0 years\n
\n\n C. 8.0 years\n
\n\n D. 10 years\n
\n\n [1]\n
\n\n C\n
\n\n A nucleus of americium-241 has 146 neutrons. This nuclide decays to neptunium through alpha emission.\n
\n\n Complete the nuclear equation for this decay.\n
\n\n \n
\n [2]\n
\n\n \n ✓\n
\n\n \n ✓\n
\n\n \n state and explain whether the second law of thermodynamics is violated.\n \n
\n\n [2]\n
\n\n \n not violated ✔\n \n
\n\n \n the entropy of the surroundings must have increased\n
\n \n \n OR\n \n \n
\n the overall entropy of the system and the surroundings is the same or increased ✔\n \n
\n Outline\n \n two\n \n reasons why both models predict that the motion is simple harmonic when\n \n is small.\n
\n\n [2]\n
\n\n \n \n For both models:\n \n \n
\n displacement is ∝ to acceleration/force «because graph is straight and through origin» ✓\n
\n displacement and acceleration / force in opposite directions «because gradient is negative»\n
\n \n \n OR\n \n \n
\n acceleration/«restoring» force is always directed to equilibrium ✓\n
\n This item was essentially encouraging candidates to connect concepts about simple harmonic motion to a physical situation described by a graph. The marks were awarded for discussing the physical motion (such as \"the acceleration is in the opposite direction of the displacement\") and not just for describing the graph itself (such as \"the slope of the graph is negative\"). Most candidates were successful in recognizing that the acceleration was proportional to displacement for the first marking point, but many simply described the graph for the second marking point.\n
\n\n Show that the rotational kinetic energy is\n \n \n Lω\n \n where\n \n L\n \n is the angular momentum of the system.\n
\n\n [1]\n
\n\n \n E\n \n \n k\n \n «=\n \n \n ω\n \n \n 2\n \n =»\n \n (\n \n \n ω\n \n )\n \n ω\n \n =\n \n \n Lω\n \n ✓\n
\n\n
\n\n \n Accept equivalent methods\n \n
\n\n Outline, by reference to nuclear binding energy, why the mass of a nucleus is less than the sum of the masses of its constituent nucleons.\n
\n\n [2]\n
\n\n according to Δ\n \n E\n \n = Δ\n \n mc\n \n \n 2\n \n / identifies mass energy equivalence ✓\n
\n\n
\n\n energy is released when nucleons come together / a nucleus is formed «so nucleus has less mass than individual nucleons»\n
\n\n \n \n OR\n \n \n
\n\n energy is required to «completely» separate the nucleons / break apart a nucleus «so individual nucleons have more mass than nucleus» ✓\n
\n\n
\n\n \n Accept protons and neutrons.\n \n
\n\n Still several answers that thought that the nucleus needed to gain energy to bind it together. Most candidates scored at least one for recognising some form of mass/energy equivalence, although few candidates managed to consistently express their ideas here.\n
\n\n Discuss the variation in the power output of the motor with distance from the lower station.\n
\n\n [2]\n
\n\n The pd across the motor increases as the tram travels up the track ✓\n
\n\n (As the current is constant), the power output also rises ✓\n
\n\n The radius of the dwarf planet Pluto is 1.19 x 10\n \n 6\n \n m. The acceleration due to gravity at its surface is 0.617 m s\n \n −2\n \n .\n
\n\n Determine the escape speed for an object at the surface of Pluto.\n
\n\n [4]\n
\n\n \n AND\n \n seen ✓\n
\n\n \n ✓\n
\n\n Leading to\n \n ✓\n
\n\n 1.2 km s\n \n −1\n \n ✓\n \n \n
\n\n The radius of the Earth is R. A satellite is launched to a height\n \n h\n \n =\n \n above the Earth’s surface.\n
\n\n What is\n \n ?\n
\n\n
\n A.\n \n
\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n The students vary\n \n V\n \n and measure the time\n \n T\n \n for the ball to move\n \n once\n \n from one plate to the other. The table shows some of the data.\n
\n\n \n
\n
\n\n 0.02 «kV» ✓\n
\n\n The standing wave on the string creates a travelling sound wave in the surrounding air.\n
\n\n Outline\n \n two\n \n differences between a standing wave and a travelling wave.\n
\n\n [2]\n
\n\n travelling waves transfer energy\n \n \n OR\n \n \n standing waves don’t ✓\n
\n\n amplitude of oscillation varies along a standing wave\n \n \n OR\n \n \n is constant along a travelling wave ✓\n
\n\n standing waves have nodes and antinodes\n \n \n OR\n \n \n travelling waves don’t ✓\n
\n\n points in an internodal region have same phase in standing waves\n \n \n OR\n \n \n different phase in travelling waves ✓\n
\n\n This question was answered well. Students showed to be familiar with the differences between standing and travelling waves. In SL they had to identify two differences, so that proved to be more challenging.\n
\n\n Suggest one problem that is faced in dealing with the waste from nuclear fission reactors. Go on to outline how this problem is overcome.\n
\n\n [2]\n
\n\n Waste is very hot …\n
\n\n … So has to be placed in cooling ponds to transfer the (thermal) energy away ✓\n
\n\n
\n\n \n OR\n \n
\n\n Waste is very radioactive … ✓\n
\n\n … So has to be placed in cooling ponds to absorb this radiation\n
\n\n \n OR\n \n
\n\n … So has to be handled remotely\n
\n\n \n OR\n \n
\n\n … So has to be transported in crash resistant casings / stored on site ✓\n
\n\n
\n\n \n OR\n \n
\n\n Waste will be radioactive for thousands of years … ✓\n
\n\n … So storage needs to be (eventually) in geologically stable areas ✓\n
\n\n \n Calculate\n \n F.\n \n \n
\n\n [2]\n
\n\n \n «clockwise moments = anticlockwise moments»\n
\n \n
\n \n 50 × 2cos 60 =\n \n N\n \n \n W\n \n × 4sin 60 ✔\n \n
\n\n \n \n «\n \n \n \n »\n \n \n
\n\n \n \n F\n \n =\n \n 14.4«\n \n N\n \n » ✔\n \n \n
\n\n Very few candidates could take moments about any point and correct answers were rare both at SL and HL.\n
\n\n \n Outline,\n \n without\n \n calculation, how the internal resistance can be determined from this graph.\n \n
\n\n [2]\n
\n\n \n determine the gradient «of the line of best-fit» ✔\n
\n \n
\n \n \n r\n \n is the negative of this gradient ✔\n \n
\n\n Estimate the power input to the heating element. State an appropriate unit for your answer.\n
\n\n [2]\n
\n\n energy required for milk entering in 1 s = mass x specific heat x 73 ✓\n
\n\n 16 kW\n \n \n OR\n \n \n 16000 W ✓\n
\n\n
\n\n \n \n MP1\n \n is for substitution into mcΔT regardless of power of ten.\n \n
\n\n \n Allow any correct unit of power (such as\n \n J s\n \n -1\n \n \n OR\n \n kJ s\n \n -1\n \n \n ) if paired with an answer to the correct power of 10 for\n \n MP2\n \n .\n \n
\n\n Most candidates recognized that this was a specific heat question and set up a proper calculation, but many struggled to match their answer to an appropriate unit. A common mistake was to leave the answer in some form of an energy unit and others did not match the power of ten of the unit to their answer (e.g. 16 W).\n
\n\n \n Show that, when the speed of the train is 10 m s-1, the frequency of the periodic force is 0.4 Hz.\n \n
\n\n [1]\n
\n\n \n time period\n \n
\n\n \n \n T = «\n \n \n \n »\n \n \n \n = 2.5 s\n \n \n \n \n AND\n \n f =\n \n \n \n \n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n \n evidence of f =\n \n \n \n ✔\n \n \n
\n\n \n \n \n Answer 0.4 Hz is given, check correct working is shown.\n \n \n \n
\n\n The question was correctly answered by almost all candidates.\n
\n\n Outline why a force acts on the Moon.\n
\n\n [1]\n
\n\n gravitational attraction/force/field «of the planet/Moon» ✔\n
\n\n \n Do not accept “gravity”\n \n .\n
\n\n This was generally well answered, although some candidates simply used the vague term “gravity” rather than specifying that it is a gravitational force or a gravitational field. Candidates need to be reminded about using proper physics terms and not more general, “every day” terms on the exam.\n
\n\n The centres of two identical fixed conducting spheres each of charge +\n \n Q\n \n are separated by a distance\n \n D\n \n . C is the midpoint of the line joining the centres of the spheres.\n
\n\n \n
\n
\n\n Constant, non-zero within spheres ✓\n
\n\n A clear, non-zero positive minimum at C ✓\n
\n\n Symmetric bowl shaped up curved shape in between ✓\n
\n\n
\n\n \n
\n \n Do\n \n not\n \n allow a bowl shaped down curve for\n \n MP3\n \n .\n \n
\n\n Two identical containers X and Y each contain an ideal gas. X has\n \n N\n \n molecules of gas at an absolute temperature of\n \n T\n \n and Y has 3\n \n N\n \n molecules of gas at an absolute temperature of\n \n What is the ratio of the pressures\n \n ?\n
\n\n \n
\n A.\n \n
\n\n B.\n \n
\n\n C.\n \n
\n\n D.\n \n
\n\n [1]\n
\n\n C\n
\n\n Suggest, for the change A ⇒ B, whether the entropy of the gas is increasing, decreasing or constant.\n
\n\n [2]\n
\n\n Increasing ✓\n
\n\n because thermal energy/heat is being provided to the gas « and temperature is constant,\n \n ✓\n
\n\n The player kicks the ball again. It rolls along the ground without sliding with a horizontal velocity of\n \n . The radius of the ball is\n \n . Calculate the angular velocity of the ball. State an appropriate SI unit for your answer.\n
\n\n [1]\n
\n\n \n \n ✓\n \n
\n\n \n
\n Unit must be seen for mark\n \n
\n \n Accept Hz\n \n
\n\n \n Accept\n \n \n
\n\n Sketch, on the axes, how the electric potential V due to the two charges varies with the distance r from the centre of the left charge. No numbers are required. Your graph should extend from r = 0 to r = D.\n
\n\n \n
\n [3]\n
\n\n Constant, non-zero within spheres ✓\n
\n\n A clear, non-zero positive minimum at C ✓\n
\n\n Symmetric bowl shaped up curved shape in between ✓\n
\n\n
\n\n \n
\n \n Do\n \n not\n \n allow a bowl shaped down curve for\n \n MP3\n \n .\n \n
\n\n \n Suppose the star could contract to half its original radius without any loss of mass. Discuss the effect, if any, this has on the total energy of the planet.\n \n
\n\n [2]\n
\n\n \n \n \n ALTERNATIVE 1\n \n \n
\n \n
\n \n «at the position of the planet» the potential depends only on the mass of the star /does not depend on the radius of the star ✔\n
\n \n
\n \n the potential will not change and so the energy will not change ✔\n
\n \n
\n \n \n \n ALTERNATIVE 2\n \n \n
\n \n
\n \n r / distance between the centres of the objects / orbital radius remains unchanged ✔\n
\n \n
\n \n since\n \n \n \n , energy will not change\n \n ✔\n \n \n
\n\n
\n\n A large number of candidates thought that the total energy of the planet would change, mostly double.\n
\n\n \n Radioactive decay is said to be “random” and “spontaneous”. Outline what is meant by each of these terms.\n \n
\n\n \n Random:\n \n
\n\n \n Spontaneous:\n \n
\n\n [2]\n
\n\n \n \n random:\n \n
\n it cannot be predicted which nucleus will decay\n
\n \n \n OR\n \n \n
\n it cannot be predicted when a nucleus will decay ✔\n
\n \n
\n \n \n NOTE: OWTTE\n \n
\n \n
\n
\n\n \n \n spontaneous:\n \n
\n the decay cannot be influenced/modified in any way ✔\n
\n \n
\n \n \n NOTE:\n \n \n OWTTE\n \n
\n \n
\n increasing the distance between the diffraction grating and the screen.\n
\n\n [1]\n
\n\n no change\n \n ✓\n \n
\n\n Outline, by reference to nuclear binding energy, why the mass of a nucleus is less than the sum of the masses of its constituent nucleons.\n
\n\n [2]\n
\n\n according to Δ\n \n E\n \n = Δ\n \n mc\n \n \n 2\n \n / identifies mass energy equivalence ✓\n
\n\n
\n\n energy is released when nucleons come together / a nucleus is formed «so nucleus has less mass than individual nucleons»\n
\n\n \n \n OR\n \n \n
\n\n energy is required to «completely» separate the nucleons / break apart a nucleus «so individual nucleons have more mass than nucleus» ✓\n
\n\n
\n\n \n Accept protons and neutrons.\n \n
\n\n Still several answers that thought that the nucleus needed to gain energy to bind it together. Most candidates scored at least one for recognising some form of mass/energy equivalence, although few candidates managed to consistently express their ideas here.\n
\n\n Show that the rotational kinetic energy is\n \n \n Lω\n \n where\n \n L\n \n is the angular momentum of the system.\n
\n\n [1]\n
\n\n \n E\n \n \n k\n \n «=\n \n \n ω\n \n \n 2\n \n =»\n \n (\n \n \n ω\n \n )\n \n ω\n \n =\n \n \n Lω\n \n ✓\n
\n\n
\n\n \n Accept equivalent methods\n \n
\n\n Discuss, for this process, the changes that occur in the density of the gas.\n
\n\n [2]\n
\n\n density decreases ✓\n
\n\n volume is increased\n \n \n AND\n \n \n mass/number of particles remains constant ✓\n
\n\n Show that the final angular velocity of the bar is about\n \n .\n
\n\n [2]\n
\n\n \n \n ✓\n \n
\n\n \n \n ✓\n \n
\n\n
\n\n \n \n Other methods are possible.\n
\n Answer 3 given so look for correct working\n
\n At least 2 sig figs for MP2.\n \n \n
\n Explain why the gas in configuration B has a greater number of microstates than in A.\n
\n\n [3]\n
\n\n Configuration A has only one microstate ✓\n
\n\n In configuration B, pairs of particles can be swapped between the halves ✓\n
\n\n Every such change gives rise to a new microstate «so there is a large number of microstates in B» ✓\n
\n\n There is an advantage and a disadvantage in using two masses that are almost equal.\n
\n\n State and explain the advantage with reference to the magnitude of the acceleration that is obtained.\n
\n\n [2]\n
\n\n the acceleration would be small/the time of fall would be large ✔\n
\n\n easier to measure /a longer time of fall reduces the % error in the time of fall and «hence acceleration» ✔\n
\n\n \n Do not accept ideas related to the mass/moment of inertia of the pulley\n \n .\n
\n\n Q 1 b) was quite well answered. Only the weakest candidates presented difficulty in understanding simple mechanics.\n
\n\n \n The molar mass of helium is 4.0 g mol\n \n -1\n \n . Show that the mass of a helium atom is 6.6 × 10\n \n -27\n \n kg.\n \n
\n\n [1]\n
\n\n \n \n \n \n «kg»\n \n \n \n
\n \n \n
\n \n \n \n OR\n \n
\n \n \n
\n \n 6.64\n \n ×\n \n 10\n \n \n \n −27\n \n \n \n \n \n «kg»\n \n \n \n ✔\n \n \n
\n\n
\n\n The mark was awarded for a clear substitution or an answer to at least 3sf. Many gained the mark for a clear substitution with a conversion from g to kg somewhere in their response. Fewer gave the answer to the correct number of sf.\n
\n\n The missing section of insulation is 0.56 m long and the external radius of the pipe is 0.067 m. The emissivity of the pipe surface is 0.40. Determine the energy lost every second from the pipe surface. Ignore any absorption of radiation by the pipe surface.\n
\n\n [3]\n
\n\n use of\n \n where\n \n T\n \n = 357 K ✓\n
\n\n use of\n \n « = 0.236 m\n \n 2\n \n » ✓\n
\n\n \n P\n \n = 87 «W» ✓\n
\n\n
\n\n \n Allow 85 – 89 W for\n \n MP3\n \n .\n \n
\n\n \n Allow ECF for\n \n MP3\n \n .\n \n
\n\n Candidates at both levels were able to recognize that this was a blackbody radiation question. One common mistake candidates made was not calculating the area of a cylinder properly. It is important to remind candidates that they are expected to know how to calculate areas and volumes for basic geometric shapes. Other common errors included the use of T in Celsius and neglecting to raise T ^4. Examiners awarded a large number of ECF marks for candidates who clearly showed work but made these fundamental errors.\n
\n\n Explain why the change of entropy for the gas during the process BC is equal to zero.\n
\n\n [1]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n «the process is adiabatic so» ΔQ = 0 ✓\n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n
\n\n The compression is reversible «so ΔS = 0» ✓\n
\n\n
\n\n \n \n OWTTE\n \n \n
\n\n The quantity of trapped gas is 53.2 mol. Calculate the thermal energy removed from the gas during process CA.\n
\n\n [2]\n
\n\n «W = 0 so» Q = ΔU ✓\n
\n\n «ΔU =\n \n × 53.2 × R × (351 – 27) so » ΔU = 2.15 × 10\n \n 5\n \n «J» ✓\n
\n\n
\n\n \n \n Award [2]\n \n for\n \n BCA\n \n \n
\n\n Show that the surface temperature of\n \n δ\n \n Vel A is about 9000 K.\n
\n\n [1]\n
\n\n correct substitution into\n \n OR 9350 K ✓\n
\n\n \n Determine the fractional uncertainty in\n \n v\n \n when\n \n T\n \n = 2.115 s, correct to\n \n one\n \n significant figure.\n \n
\n\n [2]\n
\n\n \n \n \n \n AND\n \n \n \n ✔\n \n
\n\n \n \n «\n \n »0.04\n \n ✔\n \n \n \n
\n\n \n \n \n NOTE: Accept 4 %\n \n \n \n
\n\n Predict from the equation whether the value of\n \n found experimentally will be larger, the same or smaller than the value of\n \n calculated directly.\n
\n\n [2]\n
\n\n \n \n ALTERNATIVE 1\n \n \n
\n\n \n \n \n
\n\n \n \n \n OR\n \n \n \n
\n\n \n centripetal force is larger «than\n \n » /\n \n is smaller «than centripetal»\n \n \n ✓\n \n
\n\n \n «so» experimental\n \n \n \n \n \n is smaller «than calculated value»\n \n \n ✓\n \n
\n\n
\n\n \n \n ALTERNATIVE 2\n \n \n \n \n (refers to graph)\n \n
\n \n
\n \n reference to «friction force is» a systematic error «and does not affect gradient»\n \n \n ✓\n \n
\n\n \n «so»\n \n \n \n \n \n is the same\n \n \n ✓\n \n
\n\n
\n\n \n \n MP2 awarded only with correct justification.\n
\n Candidates can gain zero, MP1 alone or full marks.\n \n \n
\n \n \n OWTTE\n \n \n
\n\n Most successful candidates chose to consider a single point then concluding that the calculated\n \n mr\n \n would be smaller than the real value as\n \n W\n \n < centripetal force, or even went into analysing the dependence of the frictional force with\n \n W\n \n . Many were able to deduce this. Some candidates thought that a graph would still have the same gradient (if friction was constant) and mentioned systematic error, so\n \n mr\n \n was not changed which was also accepted.\n
\n\n \n Radioactive decay is said to be “random” and “spontaneous”. Outline what is meant by each of these terms.\n \n
\n\n \n Random:\n \n
\n\n \n Spontaneous:\n \n
\n\n [2]\n
\n\n \n \n random:\n \n
\n it cannot be predicted which nucleus will decay\n
\n \n \n OR\n \n \n
\n it cannot be predicted when a nucleus will decay ✔\n
\n \n
\n \n \n NOTE: OWTTE\n \n
\n \n
\n
\n\n \n \n spontaneous:\n \n
\n the decay cannot be influenced/modified in any way ✔\n
\n \n
\n \n \n NOTE:\n \n \n OWTTE\n \n
\n \n
\n A comet orbits the Sun in an elliptical orbit. A and B are two positions of the comet.\n
\n\n \n
\n Explain, with reference to Kepler’s second law of planetary motion, the change in the kinetic energy of the comet as it moves from A to B.\n
\n\n [3]\n
\n\n The areas swept out in unit time by the Sun-comet line are the same at A and B ✓\n
\n\n At B, the distance is greater hence the orbital speed/distance moved in unit time is lower «so that the area remains the same» ✓\n
\n\n A decrease in speed means that the kinetic energy also decreases ✓\n
\n\n Draw, on the axes, a graph to show the variation with\n \n t\n \n of the displacement of particle Q.\n
\n\n [2]\n
\n\n oscillation in antiphase ✓\n
\n\n smaller amplitude than P ✓\n
\n\n
\n \n
\n Although there were good answers which scored full marks, there were a significant number of wrong answers where the amplitude was the same or not consistent throughout, or the wave drawn was not in antiphase of the original sketch.\n
\n