2024 SCGS Prelim P2

1 SINGAPORE CHINESE GIRLS’ SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR CANDIDATE NAME CLASS 4 REGISTER NUMBER CENTRE NUMBER INDEX NUMBER PHYSICS 6091/2 (Revised) Monday 26 August 2024 1 hour 45 mins Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Section A Answer all questions. Section B Answer one question only. Question 11 has a choice of parts to answer. 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 21 printed pages and a blank page. For Examiner’s Use Section A 70 Section B 10 Total 80

2 SECTION A Answer all the questions in this section. 1 A car of mass m is travelling along a straight, horizontal road at a constant speed v. At time t = 0, the driver of the car sees an obstruction in the road ahead of the car and applies the brakes. The car does not begin to decelerate at t = 0. (a) Explain why the car does not begin to decelerate at t = 0. .......................................................................................................................................... ……………………………………………………………………………………………………. .......................................................................................................................................... [1] Fig. 1.1 is the distance–time graph for the car from t = 0. Fig. 1.1 (b) Describe the motion of the car throughout the 5 s of travel. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… [3] (c) Determine the initial speed v of the car. v = ………………….. [2] 0 0 20 40 60 1 2 3 4 time / s distance / m 5

3 (d) When the car is decelerating, there is a constant resistive force F on the car due to the brakes. The deceleration of the car is greater than and is not constant. Explain why (i) the deceleration of the car is greater than , ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. (ii) the deceleration is not constant. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. [1] [1] [ Total : 8 m ] F m F m

4 2 Fig. 2.1 shows a sign that extends over a road. Fig. 2.1 The mass of the sign is 3.4 x 103 kg. (a) The weight of the sign acts at a horizontal distance of 1.8 m from the centre of the support post. Point P is a horizontal distance of 1.3 m from the centre of the support post. (i) Calculate the moment about P due to the weight of the sign. moment = ………………. [2] (ii) A rectangular concrete block is positioned on the other side of the support post with its centre of gravity a horizontal distance of 70 cm from the centre of the support post. Given the sign is horizontal, calculate the weight of the concrete block. weight = ……………. [2] m 1.8 W 1.3 m concrete block P 70 cm support post sign ACCIDENT SLOW DOWN

5 (b) (c) The concrete block is removed. Describe and explain what happens to the sign in terms of moments. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. A student suggests that the concrete block be placed with its largest face horizontally to increase the stability of the road sign. Explain if this suggestion is correct. [2] …………………………………………………………………………………………………… …………………………………………………………………………………………………… [1] [ Total : 7 m ]

6 3 A bungee jumper falls from a bridge above a river, as shown in Fig. 3.1. Fig. 3.1 ( not to scale) The man starts from position A in Fig. 3.1. The elastic cord starts to stretch at position C and he stops for the first time at position D. He continues to rise and fall. (a) Explain, in terms of the forces acting, why the man is undergoing increasing deceleration between C and D. ………………………………………………………………………………………………………… …………………………………………………………………………………………………….…... ……………………………………………………………………………………………….……….. …………………………………………………………………………………………………….….. [2] (b) Fig. 3.2 shows the values for the gravitational potential energy of the man, the kinetic energy of the man and the elastic potential energy in the cord at A, C and D. You may ignore the effect of air resistance in this question. Fig. 3.2 Complete Fig. 3.2 to show the kinetic energy of the man at C and the elastic potential energy in the cord at D. [2]

7 (c) The man has a mass of 50 kg. Using values from Fig. 3.2, calculate the vertical distance between A and C. vertical distance = ……………. [2] [ Total : 6 m ]

8 cube liquid pump 0.040 m air m 0.028 valve 4 A cube of side 0.040 m is floating in a container of liquid. Fig. 4.1 shows that the surface of the liquid is 0.028 m above the level of the bottom face of the cube. Fig. 4.1 The pressure of the air above the cube exerts a force on the top face of the cube. The valve is closed. (a) Given that the density of the liquid in the container is 1500 kg/m3 and the atmospheric pressure is 1.02 x 105 N/m2. Calculate (i) the pressure at a depth of 0.028 m, and pressure = ……………………. [2] (ii) the force on the bottom face of the cube. force = ………………. [2] (b) The valve is opened and liquid is pumped into the container. The surface of the liquid rises a small distance but the cube remains with its bottom face 0.028 m below the surface of the liquid. (i) Explain why the cube is able to remain at the same height in the liquid. …………………………………………………………………………………………. ………………………………………………………………………………………….. …………………………………………………………………………………………. [2] (ii) Suggest one reason why this is not an efficient method of lifting up the cube. ………………………………………………………………………………………..….. …………………………………………………………………………………………... [1] [ Total : 7 m ]

9 5 (a) Explain what is meant by critical angle. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] (b) (i) Diamonds are attractive because of their ability to reflect light. The critical angle for diamond in air is 24o. Calculate the re