Bedok Green Prelim P2

© BGSS 2024 [Turn Over 2 For examiner’s use SECTION A [ 70 marks ] Answer all questions in this section. 1 Fig. 1.1 shows three forces acting on an object and keeping it in equilibrium. Fig. 1.1 Given that F1 is perpendicular to the vertical, determine the forces F1 and F2. Include a labelled scaled vector diagram in your answer. scale: ………………………………….. F1 = ……………………….. F2 = ………………………..[4] 30° F2 F1 10 N vertical

© BGSS 2024 [Turn Over 3 For examiner’s use 2 Car A is travelling at a uniform speed of 10 m/s. The driver sees an obstacle at time = 0 s and applies the brakes. Fig. 2.1 shows the speed time graph of car A, starting from the time he first sees the obstacle. Fig. 2.1 (a) Determine (i) the reaction time of the driver in car A, reaction time = …………………..[1] (ii) the deceleration of car A. deceleration = ……………………[2] speed / m/s time / s A B

© BGSS 2024 [Turn Over 4 For examiner’s use (b) At time = 0 s, the driver of car B, travelling at an initial speed of 15 m/s applies the brakes immediately when he first sees the obstacle. The speed-time graph of car B is shown in Fig. 2.1. (i) State which car travelled a longer distance before coming to a complete stop. Give an explanation for your answer. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. ……………………………………………………..……………………[2] (ii) Using the graph in Fig. 2.1, explain the changes in the braking force exerted by car B. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. ……………………………………………………..……………………[2]

© BGSS 2024 [Turn Over 5 For examiner’s use 3 Fig. 3.1 shows the presence of gas molecules, in a cylinder. Fig. 3.1 Using the kinetic model of matter, explain the following: (a) When the piston is pushed into the cylinder, the gas pressure increases. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………[2] (b) The piston is pushed out of the cylinder as temperature of the cylinder increases. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………[2] gas piston cylinder

© BGSS 2024 [Turn Over 6 For examiner’s use 4 Fig. 4.1 shows ultrasound being used to find the distance between a submarine and an underwater object. Fig. 4.1 Fig. 4.2 shows the trace of the pulse sent from the submarine and the reflected pulses that returns. Fig. 4.2 (a) Explain why the amplitude of the reflected pulse is different from the original pulse. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………[2] (b) Given that the speed of sound in water is 1500 m/s, calculate (i) the time taken for the first pulse to travel from the submarine to the object, time = ……………..[1] (ii) the distance between the object and the submarine. distance = ……………..[2] sea original pulse 50 ms reflected pulse distance object

© BGSS 2024 [Turn Over 7 For examiner’s use 5 “Cat’s eyes” are glass prisms set in rubber mould mounted in a box. They are often used on roads to mark out lanes by reflecting light from the head lamp of cars at night. Fig. 5.1 shows the diagram of a “Cat’s eye”. Fig. 5.1 The refractive index of the glass prism is 1.8. (a) The speed of light in air is 3.0 x 108 m/s. Calculate the speed of light in the glass prism. speed of light in prism = ………………………[2] (b) Calculate the critical angle of the glass prism. critical angle = ……………………[2] light rays from head lamps glass prism rubber air layer 45° 45° A B

© BGSS 2024 [Turn Over 8 For examiner’s use (c) Describe, with a reason, what happens to the light ray from the head lamps when it hits the glass prism at sides A and B. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………….……….……………………………………………….[2] 6 Fig. 6.1 shows the graph of resistance of a thermistor against temperature. Fig. 6.1 A student sets up the circuit in Fig. 6.2. The heating filament is mounted close to the thermistor. Fig. 6.2 resistance / Ω temperature / °C 10 Ω heating element thermistor 10 Ω S 1.5 V

© BGSS 2024 [Turn Over 9 For examiner’s use (a) When switch S is closed, the lamp fails to light up at first, but does so at a later time. Explain why this happens. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………….……….……………………………………………….[2] (b) The lamp barely lights up when a current of 13.6 mA flows through it. Using the information from Fig. 6.1, determine the minimum temperature required for the lamp to light up. minimum temperature = ………………………[3]

© BGSS 2024 [Turn Over 10 For examiner’s use 7 A student sets up a circuit to investigate the strength of an electromagnet as shown in Fig. 7.1. Fig. 7.1 (a) (i) State what happens to the compass needle when the switch is closed. …………………………………………………………………………….. ………………………………………………………………………….[1] (ii) Explain your answer in (a)(i). …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. ………………………………………………………………………….[2] low frequency, 12 V a.c. power supply solenoid with soft iron core compass needle pointing north

© BGSS 2024 [Turn Over 11 For examiner’s use To protect the coil, the student adds a fuse to the circuit and changes the power supply to a battery, as shown in Fig. 7.2. Fig. 7.2 This time, when he closes the switch, the fuse ‘blows’ and the compass needle turns. (b) (i) Explain why the fuse ‘blows’. …………………………………………………………………………….. ………………………………………………………………………….[1] (ii) Suggest why does the needle move after the fuse ‘blows’. …………………………………………………………………………….. ………………………………………………………………………….[1] (iii) State the direction which the compass needle points to. …………………………………………………………………………….. ………………………………………………………………………….[1] 12 V battery solenoid with soft iron core compass needle pointing north