AES 2025 Physics Prelim P1 & P2 MS

Page 1 of 5 Secondary 4 Express Preliminary Examination 2025 Physics 6091 Answer Keys and Marking Scheme PAPER 1 – 40 M Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 C B D B B B A C C D Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 D C A D D C A A B C Q21 Q22 Q23 Q24 Q25 Q26 Q27 Q28 Q29 Q30 B C A C C B A C C B Q31 Q32 Q33 Q34 Q35 Q36 Q37 Q38 Q39 Q40 D D D A A C A A C B PAPER 2 SECTION A – 70 M 1a The gradient of the graph is not constant. B1 1b 60 - 20v = 2.4 - 1.4 = 40 m/s C1 A1 1c Speed (velocity) of the ball increases, air resistance increases until it balances the weight of the ball. Since resultant force is zero, ball moves at maximum constant speed (velocity). B1 B1 2ai Zero resultant force B1 2aii Constant speed B1 2b The resultant force is equal to the frictional force. (Or opposite to velocity) The box will decelerate constantly and comes to a stop. B1 B1 2c The other force is the reaction force of the ground on the box, which is equal and opposite to the weight. B1 B1 3a 621KE = 1.2 10 0.0402 = 960J    C1 A1

Page 2 of 5 3bi 2 0.040a = 0.60 = 0.066667 m/s 6F =1.2 10 0.066667 = 80000N = 80kN  M1 M1 A1 3bii 960 = 80000 d d = 0.012m  [ecf from 3a] C1 A1 4a 4.2 J of energy is transferred into the internal store of 1 g of water to raise its temperature by 1°C. B1 4b Q = 250 4.2 30 = 32000J(2sf) C1 A1 4c 100 10 60 = m 334 m = 180g    C1 A1 5ai Using a measuring tape, measuring the distance between two wavefronts. B1 5aii 3.8 m B1 5aiii 3.8v = 4.0 = 0.95m/s [ecf from 5aii] C1 A1 5b The speed of wave decreases when the depth decreases nearer to shore. Since frequency is constant, wavelength decreases. B1 B1 6a Electrons in Q is induced on the side near to P. Therefore, the positively charged sphere P moves towards Q because unlike charges attract. B1 B1 6b Electrons in Q move into P until both spheres are equally charged. P then moves away from Q because like charges repel. B1 B1 7a V = 2.0 9.0 = 18 V  C1 A1 7b 4.0I = 3.0 = 1.3 A(2sf) C1 A1

Page 3 of 5 7c Effective resistance of the circuit increases, leading to a smaller current and potential difference in the light bulb. Light bulb is less bright. B1 B1 8a When the alternating current changes repeatedly, the polarity at X alternates between North and South poles. This causes the magnet to move left and right due to attraction and repulsion. As the paper cone vibrates, a series of compressions and rarefactions are produced, and sound is transferred in the form of longitudinal wave. B1 B1 B1 8bi No continuous sound is produced (because the paper cone does not vibrate). [Accept only one sound can be heard.] B1 8bii The sound becomes louder (due to greater vibration). B1 9a Due to the changing magnetic field linking the coil, an emf is induced in the coil and current flows to the ammeter. B1 B1 9b The ammeter reading increases and oscillates at a higher frequency. This is due to the rate of rotation of the spindle increases, leading to greater rate of change of magnetic field. B1 B1 9c M = 50 0.30 = 15 Nm  C1 A1 10ai 5.36 m 1.24 m B1 10aii 5.36 + 1.24s = 1.50 = 4.40 m/s [ecf from 10ai] C1 A1 10aiii GPE = 50 10 6.6 = 3300 J  C1 B1 10aiv The energy in the gravitational potential store of boy is transferred mechanically to his kinetic store from O to A. [reject from O to B] As the trampoline stretches from A to B, the energy in the kinetic store is transferred mechanically to the elastic potential store of the trampoline. B1 B1 10bi 2.50 s B1

Page 4 of 5 10bii From t = 1.50 to 1.75 s, his average velocity is 0.098 ( 1.24) 8.88m/s0.25 −− = which is greater compared to 2.57 0.98 6.36m/s0.25 − = from t = 1.75 s to 2.00 s. Since the velocity is decreasing, the boy is going through deceleration. B1 B1 11a The nuclear force within the nucleus is not enough to bind the nucleons together. B1 11b It has 2 neutrons and 2 protons (identical to a helium nucleus). B1 11c 226 222 4 88 86 2 →+Ra Rn B1 – balanced equation B1 – correct reactant and products B2 11d Decay of radium is spontaneous as it decays due to its unstable nucleus. No neutron is directed at radium to start the reaction which occurs in nuclear fission. B1 B1 11e 100 2 2 2 = 12.5 g 8.3 3 = 24.9 days C1 A1 11f Alpha particles are highly ionising and can damage the cells that are near them. This could cause cell death, cell mutation or even cancer. B1 B1 PAPER 2 SECTION B – 10 M 12a When light moves from the optically less dense air to optically denser water, the speed of light decreases. B1 B1 12b sin 20n = sin 15 = 1.321 sin 601.321 sin r r 40.9 = = C1 A1 12c The angle of incidence in the optically denser medium such that the angle of refraction in the optically less dense medium is 90°. B1 12d 11.321 = sin c c = 49.2 [ecf from 12b] M1

Page 5 of 5 The angle of incidence of ray 2 is 40.9°. As this angle is less than the critical angle, ray 2 will exit the water droplet and bend away from the normal. B1 B1 12e Add water into a beaker (or any curved container). Placing an object at less than twice the focal length of the water will produce a magnified image. B1 B1 13a With the fixed resistor, the potential difference across it can be varied within a range. This allows the alarm bell to be switched on or off. B1 B1 13b 90 Ω B1 13c 50V = 20 50+90 = 7.14 V  C1 A1 13d When the temperature increases, the resistance of the thermistor decreases. By potential divider rule, the potential difference across the resistor increases, activating the bell. B1 B1 13e 220P = 50+90 = 2.86 W B1 B1 13f The change in output voltage is not significant. B1