SCGS 2025 PHY PRELIM P2 QP

1 SINGAPORE CHINESE GIRLS’ SCHOOL PRELIMINARY EXAMINATION 2025 SECONDARY FOUR CANDIDATE NAME CLASS 4 REGISTER NUMBER CENTRE NUMBER INDEX NUMBER PHYSICS 6091/2 Paper 2 27 August 2025 1 hour 45 mins Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. Candidates are reminded that all quantitative answers should include appropriate units. The use of an approved scientific calculator is expected, where appropriate. Candidates are advised to show all their working in a clear and orderly manner, as more marks are awarded for sound use of Physics than for correct answers. The number of marks is given in brackets [ ] at the end of each question or part question. Take g = 10 ms-2 or 10 Nkg-1 unless stated otherwise. This question paper consists of 24 printed pages. For Examiner’s Use Section A 70 Section B 10 Total 80

2 Section A Answer all questions. 1 Fig. 1.1 shows the descent of a skydiver from a stationary balloon. Fig. 1.1 (not to scale) The skydiver steps off the balloon at a height of 2000 m and accelerates downwards. His speed is 52 m/s at a height of 500 m. He then opens his parachute. From 400 m to ground level, he falls at constant speed. (a) The total mass of the skydiver and his equipment is 92 kg. (i) Calculate, for the skydiver, 1. the decrease in energy in the gravitational potential store as he falls from 2000 m to 500 m, decrease in energy in the gravitational potential store = ……….……………… [2] 2. the energy in the kinetic store at the height of 500 m. energy in the kinetic store = ……….……………… [2]

3 (ii) The energy in the kinetic store at 500 m is not equal to the decrease in energy in the gravitational potential store. Explain why there is a difference in the values. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………….. [1] (b) State (i) what happens to the air resistance acting on the skydiver as he falls from 2000 m to 1500 m, ………………………………………………………………………………………….. [1] (ii) the value of air resistance during the fall from 400 m to the ground. air resistance = ……….……………… [1] [ Total : 7 m ]

4 2 A block is pulled by a force X in a straight line along a rough horizontal surface, as shown in Fig. 2.1. Fig. 2.1 Assume that the total resistive force opposing the motion of the block is 0.80 N at all speeds of the block. The variation of the magnitude of the force X with time t is shown in Fig. 2.2. Fig. 2.2 (a) (i) Describe and explain the motion of the block between t = 0.0 s and t = 3.0 s. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………….. [2] (ii) Describe and explain the motion of the block between t = 3.0 s and t = 6.0 s. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………….. [2]

5 (b) Force X produces a total power of 2.0 W when moving the block between time t = 3.0 s and time t = 6.0 s. Calculate the distance moved by the block during this time interval. distance = ……….……………… [2] (c) Explain the difference in the power produced between t = 0.0 s and t = 3.0 s, and that in (b). ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………….. [1] [ Total : 7 m ]

6 3 A uniform rectangular sheet of card of weight W is suspended from a wooden rod. The card is held initially to one side, as shown in Fig. 3.1. Fig. 3.1 The card is then released. It swings on the rod and eventually comes to rest. (a) List two key forces, other than its weight and air resistance, that act on the card during the time that it is swinging. State where the forces act. 1. …………………………………………………………………………………………………. …………………………………………………………………………………………………. 2. .………………………………………………………………………………………………… …………………………………………………………………………………………… [2] (b) A student claims that the two forces listed in (a) are not an action-reaction pair. Explain whether his claim is correct or incorrect. ………………………………………………………………………………………………........... ………………………………………………………………………………………………........... ………………………………………………………………………………………………........... ……………………………………………………………………………………………….. [2] [ Total : 4 m ]

7 4 The Brownian motion of smoke particles in air may be observed using the apparatus shown in Fig. 4.1. Fig. 4.1 Fig. 4.2 Fig. 4.2 shows the motion of a smoke particle. (a) Explain the motion of the smoke particle. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………….. [2] (b) (i) Suggest what would be observed in the movement of smoke particles when the temperature in the smoke cell is increased. ………………………………………………………………………………………………... ………………………………………………………………………………………….. [1] (ii) Explain, in term of molecules, your answer to (b)(i). ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………….. [2] [ Total : 5 m ] smoke particle

8 5 (a) A semicircular glass block G is originally placed with its flat surface parallel to a vertical wall. A beam of red laser light is directed along the radius of the block and towards a point A on the wall. The distance from the centre of the glass block, O, to point A is 1.50 m. With the path of the light beam from the source unchanged, the glass block is rotated about its centre. The bright spot where the beam strikes the wall moves down from point A to B and then disappears. Fig. 5.1 shows how the spot moves from A to B as the block rotates. Fig. 5.1 (not to scale) (i) Explain why the spot disappears. ………………………………………………………………………………………………... ………………………………………………………………………………………….. [1] (ii) Determine the refractive index of the material of the glass block G. refractive index = ……….……………… [3] (iii) Explain whether AB would be longer or shorter if a higher refractive index glass block is used. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………….. [1]

9 (b) Fig. 5.2 shows a slide projector, which is an optical instrument for image projection. Light from a lamp is converged onto a slide and a convex lens is used to form an image of the slide on a screen. Fig. 5.2 Fig. 5.3 shows a slide PQ, the lens and the screen. The lamp which illuminates the slide is not shown in the figure. Fig. 5.3 (i) On Fig. 5.3, draw two rays each from P and Q, to show how a focused image of the slide is formed on the screen. Label the im