SAJC Prelim H2 P2 2025 Qn and Ans

1 SAJC 2025 Preliminary Examination / 9749 [Turn Over Class Index Number Name 24S ST. ANDREW’S JUNIOR COLLEGE JC 2 2025 Preliminary Examination PHYSICS, Higher 2 9749/02 Paper 2 Structured Questions 3rd September 2025 2 hours Candidates answer on the Question Paper. No additional materials are required. READ THESE INSTRUCTIONS FIRST Write your name, index number and Civics Group on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Answer all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 12 2 / 8 3 / 7 4 / 10 5 / 10 6 / 13 7 / 20 Total / 80 This document consists of 23 printed pages including this page.

2 SAJC 2025 Preliminary Examination / 9749 [Turn Over Data speed of light in free space, c = 3.00 x 108 m s-1 permeability of free space, o = 4  x 10-7 H m-1 permittivity of free space, o = 8.85 x 10-12 F m-1 = (1/(36)) x 10-9 F m-1 elementary charge, e = 1.60 x 10-19 C the Planck constant, h = 6.63 x 10-34 J s unified atomic mass constant, u = 1.66 x 10-27 kg rest mass of electron, me = 9.11 x 10-31 kg rest mass of proton, mp = 1.67 x 10-27 kg molar gas constant, R = 8.31 J K-1 mol-1 the Avogadro constant, NA = 6.02 x 1023 mol-1 the Boltzmann constant, k = 1.38 x 10-23 J K-1 gravitational constant, G = 6.67 x 10-11 N m2 kg-2 acceleration of free fall, g = 9.81 m s-2 Formulae uniformly accelerated motion, s = u t + ½ a t2 v2 = u2 + 2 a s work done on/by a gas, W = p V hydrostatic pressure, p =  g h gravitational potential,  = r Gm− temperature, T / K = T / oC + 273.15 pressure of an ideal gas, p = 1 3 Nm v 〈c2〉 mean translational kinetic energy of an ideal gas molecule, E = 2 3 kT displacement of particle in s.h.m., x = xo sin  t velocity of particle in s.h.m., v = v0 cos  t v =   22 0 xx − electric current I = Anvq resistors in series, R = R1 + R2 + ... resistors in parallel, 1 / R = 1 / R1 + 1 / R2 + ... electric potential, V = r Q 04 alternating current/voltage, x = xo sin  t magnetic flux density due to a long straight wire, B = μ0I 2πd magnetic flux density due to a flat circular coil, B = μ0NI 2r magnetic flux density due to a long solenoid, B = μ0nI radioactive decay, x = xo exp (- t) decay constant,  = 2/1 2ln t

3 SAJC 2025 Preliminary Examination / 9749 [Turn Over Answer all questions in the spaces provided. 1 A toy car with a rocket engine moves along a horizontal track, as shown in Fig. 1.1. Fig. 1.1 The rocket engine produces a constant forward force of 4.6 N. The car loses mass continuously as exhaust gases are produced by the rocket. (a) Use momentum considerations to explain why the rocket produces a forward force on the car. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. ………………….…….…….…….…….…….…….…….…….…….…….…….…….…….….. ……..…….…….…….…….…….…….…….…….…….…….…….…….…….…….…….. [3] (b) The variation with time t of the speed v of the car is shown in Fig. 1.2. Fig. 1.2 At time t = 2.0 s, the mass of the car is 440 g.

4 SAJC 2025 Preliminary Examination / 9749 [Turn Over (i) For the time t = 2.0 s, 1. use Fig. 1.2 to determine the acceleration of the car, acceleration = …………………… m s-2 [2] 2. use your answer in (i) part 1 to determine the magnitude of the resistive force acting on the car. force = …………………… N [2] (ii) Explain how it can be deduced that the resistive forces acting on the car increase with increase of speed. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….. [2] (c) The toy car is now re-fuelled and then rotated so that it is pointing upwards. It is suggested that the rocket engine produces sufficient force to propel the car vertically. By considering the acceleration of the car at time t = 0 in Fig. 1.2, comment on this suggestion. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. …….………………….…….…….…….…….…….…….…….…….…….…….…….…….….. ………………….…….…….…….…….…….…….…….…….…….…….…….…….…….….. ……..…….…….…….…….…….…….…….…….…….…….…….…….…….…….…….. [3]

5 SAJC 2025 Preliminary Examination / 9749 [Turn Over 2 (a) State the principle of moments. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ………………………………………………………………………………………………… [1] (b) A rigid uniform beam rests on a pivot at its centre, as shown in Fig. 2.1. Fig. 2.1 (not to scale) A load of weight 2.6 N is suspended from the beam at distance x from the pivot. A wooden cylinder of weight 4.0 N is suspended from the beam at a distance of 0.40 m from the pivot on the opposite side of the pivot to the load. The cylinder rests in a container of water. The lower part of the cylinder is immersed in the water to depth h. Initially, h is equal to 0.10 m and x is equal to 0.40 m. The system is in equilibrium. (i) Use the principle of moments to show that the upthrust U exerted by the water on the cylinder is 1.4 N. [2]

6 SAJC 2025 Preliminary Examination / 9749 [Turn Over (ii) The density of the water is 1.0 × 103 kg m–3. Calculate the area A of the circular cross-section of the cylinder. A = ………………………….. m2 [2] (c) More water is gradually added to the container in (b), so that depth h in Fig. 2.1 gradually increases. The length x is continuously adjusted so that the system remains in equilibrium. On Fig. 2.2, sketch the variation of x with h. Use the space below for any working. Fig. 2.2 [3]

7 SAJC 2025 Preliminary Examination / 9749 [Turn Over 3 (a) A planet may be assumed to be a uniform sphere. It has gravitational potential Φ at distance r from the centre of the planet. The variation with 1/r of Φ is shown in Fig. 3.1. Fig. 3.1 (i) Show that the mass of the planet is 8.8 × 1025 kg. [2]

8 SAJC 2025 Preliminary Examination / 9749 [Turn Over (ii) The period of rotation of the planet is 0.72 Earth days. A satellite in orbit around the planet remains above the same point on the surface of the planet. The speed of the satellite is 8400 m s–1. The mass of the satellite is 1200 kg. Determine the additional energy required to move the satellite from its orbit to infinity. energy required = ....................................................... J [3] (b) To move the satellite to a new, stable circular orbit closer to the planet, a short rocket thrust is requ