TJC 2025 H2 Prelim Paper 2

TEMASEK JUNIOR COLLEGE 2025 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER PHYSICS 9749/02 Paper 2 Structured Questions 29 August 2025 2 hour Candidates answer on the Question Paper. For Examiner’s Use READ THESE INSTRUCTIONS FIRST 1 Write your name and civics group in the spaces at the top of this page. 2 Write in dark blue or black pen on both sides of the paper. 3 You may use an HB pencil for any diagrams or graphs. 4 Do not use staples, paper clips, glue or correction fluid. 5 The use of an approved scientific calculator is expected, where appropriate. 6 Answer all questions 7 s.f The number of marks is given in brackets [ ] at the end of each question or part question. Total This document consists of 20 printed pages

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 2 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 or (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 Js 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 = ut + ½ at2 v2 = u2 + 2as work done on/by a gas W = p ΔV hydrostatic pressure p = gh gravitational potential  = –Gm/r temperature T/K = T/oC + 273.15 pressure of an ideal gas p = 3 1 V Nm < c2 > mean translational kinetic energy of an ideal gas molecule E = 2 3 kT displacement of particle in s.h.m. x = xosint velocity of particle in s.h.m. v = vocost = )( 22 xxo − electric current I = Anvq resistors in series R = R1 + R2 + .... resistors in parallel 1/R = 1/R1 + 1/R2 + .... electric potential V = rε4π Q o alternating current/voltage x = xo sint magnetic flux density due to a long straight wire B = 𝜇𝑜𝐼 2𝜋𝑑 magnetic flux density due to a flat circular coil B = 𝜇𝑜𝑁𝐼 2𝑟 magnetic flux density due to a long solenoid B = onI radioactive decay x = x0 exp(−t) decay constant λ = 𝑙𝑛2 𝑡1/2

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 3 [Turn over Answer all the questions in the spaces provided. 1 Fig. 1.1 shows a force diagram that represents a boat that is being lifted by two ropes so that the boat remains horizontal and travels vertically upwards at a constant speed after leaving the water. Fig. 1.1 The weight of the boat is 15000 N and the tensions in the ropes 1 and 2 are T1 and T2 respectively. (a) The position of the centre of gravity of the boat is not at its midpoint. Suggest what this implies about the distribution of mass in the boat. [1] (b) Explain two conditions required for the boat to be in a state of equilibrium while it is moving upwards. [2]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 4 (c) Determine the tension in the two ropes T1 = N T2 = N [3] (d) The two ropes are connected to a motor. Calculate the minimum power generated by the motor to lift the boat off the water onto a 30.0 m cliff within a time of 12s. P = W [2] [Total: 8] 2 An open cube is placed in a liquid of density ρ, with a length l submerged as shown in Fig. 2.1. The cross-sectional area of the cube A is constant. When the cube is displaced downwards by a small distance from the equilibrium position and released, it resulted in simple harmonic motion of the cube. The frequency f of the cube is given by 1 2 gf = l . Fig. 2.1

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 5 [Turn over In an experiment, surface water waves of speed 0.90 m s-1 and wavelength 0.45 m are generated using a dipper shown in Fig. 2.2. The generated waves are incident on the cube, causing resonance in its up-and-down motion. (a) Explain why the cube undergoes resonance. [2] (b) Calculate the length l. l = m [2] (c) Describe and explain what happens to the amplitude of the vertical oscillations of the cube after the following changes are made independently: (i) the distance between the wave crests increases, [2] (ii) some water is poured into the cube, without sinking it. [2] Fig. 2.2

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 6 (d) Explain why the value of l that you found in (b) is larger than the actual measurement of l in the experiment [2] [Total: 10] 3 A sound wave that is propagating towards the left is represented by the two graphs below. Fig. 3.1 shows the variation with position along the wave of the displacement of the air particles from their equilibrium position at time t = 0. Fig. 3.2 shows the variation with time t of the displacement of an air particle from its equilibrium position. (a) Calculate the speed of the sound wave. speed = m s-1 [2] displacement / nm t / ms 5.00 −5.00 | | | | | | 2.0 4.0 6.0 8.0 10.0 12.0 | | | | 0.7 1.4 2.1 2.8 position / m displacement / nm 5.00 −5.00 P Q R Fig. 3.1 Fig. 3.2

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 7 [Turn over (b) Fig. 3.1 shows three particles P, Q and R along the sound wave. Taking rightwards to be positive, identify the particle that is (i) instantaneously at rest at t = 0, particle = [1] (ii) at the centre of a rarefaction at t = 0. particle = [1] (iii) Explain why displacement-time graph for particle Q is represented by Fig. 3.2. [1] (c) (i) Sketch in Fig. 3.1 the graph of the wave 1.0 ms later. Label the graph Y. [2] (ii) Particle S is 0.70 m to the right of particle R. Sketch in Fig. 3.2, the graph that corresponds to particle S. Label the graph Z. [2] [Total: 9] 4 (a) Two coherent light wavetrains having the same plane of polarization meet at a point. State two conditions that must be fulfilled before totally destructive interference can occur. 1. 2. [2] (b) Fig. 4.1 shows an experiment to demonstrate interference effects with microwaves. A transmitter, producing microwaves of wavelength λ is placed in front of two slits separated by a distance a. A receiver is used to detect the strength of the resultant wave at different points along the line YZ which is at a distance D in front of the slits.

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 8 Fig. 4.1 (i) Explain, in terms of the path difference between the wavetrains emerging from the slits S1 and S2, why a series of interference maxima are produced along the line YZ. [2] (ii) State how the distance x between neighbouring maxima on the line YZ would change if the distance a was doubled while the distance D was halved. [1] (iii) In another experiment using the apparatus in Fig. 4.1, a student notices that the distances between the maxima are not equal. Suggest a reason for this difference. [1]