SJI 2018 Prelim P2

ST JOSEPH’S INSTITUTION PRELIMINARY EXAMINATION 2018 (YEAR 4) CANDIDATE NAME CLASS INDEX NUMBER PHYSICS Paper 2 6091/02 20 August 2018 1 hour 45 minutes (08:00 – 09:45) READ THESE INSTRUCTIONS FIRST Write your name, class and index number on the cover page of this Question Paper and all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions on the Question Booklet Section B Answer all questions. Question 13 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 formulae and all their working in a clear and orderly manner, as more marks are awarded for sound use of Physics than for correct answers. 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. Section A Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Section B Q11 Q12 Q13E Q13O For Examiner’s Use Section A / 50 Section B / 30 Total / 80 This document consists of 23 printed pages including this cover page [Turn Over

2 Section A Answer all the questions in this section 1 Car A moves from X to Y in a straight road at a constant acceleration of 2.0 m/s2 from rest. At the same starting time as car A, car B starts to move from Y to X at a speed of 2.0 m/s. Car B maintains the same speed throughout the whole journey. (a) Describe how the speed of car A changes with time as it moves from X to Y. …………………………………………………………………………………………... ...………………………………………………………………………………………[1] (b) Sketch the velocity-time graph of car A and car B. Taking direction from X to Y as the positive direction. [2] (c) The distance between X and Y is 1000 m. Both cars meet at time, t. (i) Express the distance travelled by car A when both cars meet, in terms of t. distance = ........................................ [1] (ii) Hence, determine the time, t when both cars meet. time = ........................................ [1] v/m/s t/s

3 2 In a pool game, ball A moves horizontally and simultaneously collides with ball B and ball C as shown in Fig 2.1. Upon collision, ball A exerts a 0.50 N force on ball C at an angle of 30° to the horizontal as shown in Fig 2.2. The resultant force acting on ball A is 0.80 N at an angle of 25° to the horizontal as shown in Fig 2.3. Fig 2.1 Fig 2.2 Fig 2.3 (a) Draw free body diagrams to show the action and reaction pair of the 0.50 N force. [1] (b) In the space below, draw a labelled diagram to show the resultant force acting on ball A due to the forces that ball B and ball C exert on ball A during the collision. Determine the magnitude of the force that ball B exerts on ball A. force = ........................................ [3] 25° 0.80 N A 30° 0.50 N C A A C B

4 (c) If the mass of all the balls are 100 g, calculate the acceleration of ball C immediately after the collision. Assume that there is negligible frictional force. acceleration = ........................................ [1] (d) It is observed that ball A continues to move fo rward after the collision. Explain why ball A continues to move forward even though the resultant force is opposite to its direction of motion. …………………………………………………………………………………………... ...………………………………………………………………………………………[1] 3 Fig. 3.1 shows a uniform rod XY of length 3.0 m suspended by two identical strings, P and Q. The weight of the rod is 10 N. Fig. 3.1 A 5.0 N load and load L are hung from the rod at point X and point Y respectively. (a) Taking moment about P, (i) calculate the moment due to the weight of the uniform rod. moment = ………………………………. [1] X Y P Q 5.0 N L 0.50 m 0.70 m

5 (ii) calculate the tension of the string, Q when the weight of load L is 15 N. tension = ………………………………. [2] (b) When the weight of load L is increased, using ideas about moment, explain why string Q will break. …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………..[2] 4 The figure below shows a student pumping air slowly into a balloon . Assume that temperature remains constant throughout the whole process. https://www.wikihow.com/Blow-Up-a-Balloon Explain, using ideas about molecules, why the balloon expands as more air is pumped into it. ………………………………………………….……………………………………………...... ……………………………………………………….………………………………………...... ………………………………………………….……………………………………………...... ……………………………………………………….………………………………………...... …………………………………………………………….…………………………………...... ………………………………………………………………….……………………………..[3] balloon balloon pump

6 5 John visited a water theme park and tried a water slide ABC as shown in Fig 5.1. John’s mass was 70 kg and the height of the water slide was 5.0 m. John slid along a horizontal surface AB, and continued down the slide at point B with a speed of 2.0 m/s. Fig 5.1 (a) Explain how the principle o f conservation of energy is applied as John slid down from B to C. …………………………………………………………………………………………... ………………………………………………………………………………………..[1] (b) Calculate the change in John’s gravitational potential energy, GPE as he slid from A to C. change in GPE = ........................................ [1] A B C 5.0 m

7 (c) The final speed of John at point C was 8.0 m/s. Calculate the work done by John against friction as he slid down the w ater slide from B to C. work done = ........................................ [2] (d) On another try, John slid from point B at the same speed of 2.0 m/s. However this time he noticed that there was less water on the slide along BC. Explain why John’s final speed at point C will be smaller than 8.0 m/s. ……………………………………………………………………………………..………... ……………………………………………………………………………………..………... …………………………………………………………………………………..………..[1] 6 A test-tube containing 100 g of glycerol at 50 °C is placed in a large container containing ice. The graph below shows how the temperature of the glycerol changes with time. The specific heat capacity of glycerol = 2.4 J/(gK) and the specific latent heat of fusion of glycerol = 420 J/g. (a) Calculate the amount of thermal energy released by the glycerol as its temperature dropped from 50 °C to 17 °C. energy = ........................................ [1] T/°C t/s 50 17 100 t

8 (b) If the rate of heat transfer remains the same throughout the whole cooling process, calculate the time, t for the temperature of the glycerol to drop again. time = ........................................ [2] (c) Explain why in real-life, the rate of heat transfer will not be constant throughout the whole cooling