SCGS 2022 Prelim P2

1 SINGAPORE CHINESE GIRLS’ SCHOOL PRELIMINARY EXAMINATION 2022 SECONDARY FOUR CANDIDATE NAME CLASS 4 REGISTER NUMBER CENTRE NUMBER INDEX NUMBER PHYSICS 6091/2 Monday 29 August 2022 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 all questions. 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 26 printed pages. For Examiner’s Use Section A 50 Section B 30 Total 80

2 SECTION A Answer all the questions in this section. 1 Fig. 1.1 shows two engineers measuring the length of a wall made from concrete. Fig. 1.1 (not to scale) The wall is 2.0 m high, 15.0 m long and 0.25 m thick. The mass of the wall is 18 000 kg. (a) The engineers measure the length of the wall in one single measurement. State the name of the measuring instrument they use. ……………………………………………………………….. [1] (b) The engineers state that the density of the concrete affects the pressure exerted by the wall on the ground but that the length of the wall does not affect this pressure. (i) Calculate the average density of the concrete. Average density = ……………….. [2] (ii) Calculate the average pressure exerted by the wall on the ground. Average pressure = …………….. [2]

3 (iii) Without further calculation, explain why doubling the length of the wall does not change the pressure that the wall exerts on the ground. ………………………………………………………………….………………………. ………………………………………………………………………………………….. ………………………………………………………………………………………...... [1] [ Total : 6 m ]

4 2 Fig. 2.1 shows a cricket ball as it comes into contact with a cricket bat. Fig. 2.1 The cricket ball has a mass of 0.16 kg and it hits the bat with a speed of 25 m / s. After being in contact with the bat for 0.0013 s, the ball rebounds with a speed of 22 m / s in the direction exactly opposite to its original direction. (a) State the difference between speed and velocity. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… …………………………………………………………………………………………………………. [2] (b) Calculate (i) the change in velocity of the cricket ball, Velocity change = ………………… (ii) the average acceleration of the ball whilst it is contact with the bat, Acceleration = ………….. [1] [2]

5 (iii) the average force exerted on the ball by the bat. Force = ……………… [2] [ Total : 7 m ]

6 3 (a) Explain what is meant by centre of gravity. ......................................................................................................................................... ......................................................................................................................................... [1] (b) A student is being weighed. The student, of weight W, stands 0.30 m from end A of a uniform plank AB, as shown in Fig. 3.1. The plank has weight 80 N and length 2.0 m. A pivot P supports the plank and is 0.50 m from end A. A weight of 70 N is moved to balance the weight of the student. The plank is in equilibrium when the weight is 0.20 m from end B. (i) Determine the weight W of the student. Weight = …………… [2] (ii) If only the 70 N weight is moved, there is a maximum weight of student that can be determined using the arrangement shown in Fig. 3.1. State and explain one change that can be made to increase this maximum weight. .................................................................................................................................. …................................................................................................................................ …................................................................................................................................ [2] [Total : 5m] 0.30 m 0.20 m 0.50 m 2.0 m 80 N N 70 A W B P Fig. 3.1 (not to scale)

7 4 Fig. 4.1 shows the variation in volume of ice when the temperature changes from -5oC to 10oC. The mass of ice is 30 g. Fig. 4.1 (a) Describe how the density of the ice changes as its temperature increases from -5oC to 0oC. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] (b) Calculate the change in the density of ice at 0oC in g/cm3. Density = ………….. [2]

8 (c) The volume of some ice cubes in a freezer decreases when they are left in the freezer for some time. This is because the ice changes from a solid to a vapour without becoming a liquid. Describe, in terms of molecules, how ice changes from solid to vapour. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] [ Total : 6 m ]

9 5 A student wishes to find out whether the energy from the radio waves emitted by mobile phones may affect a temperature rise in his brain. He first obtains the information from the mobile phone’s manufacturer shown in Fig. 5.1a. Fig. 5.1a Fig. 5.1b (a) The student switches on the phone for 6 minutes and places it next to a glass beaker containing 50 g of water (Fig. 5.1b). Calculate (i) the number of pulses of radio waves produced during the 6 minutes of call; Number of pulses = …………… [1] (ii) the total energy of the radio waves emitted during the phone call. Total energy = ………… [1]

10 (iii) the maximum temperature rise produced in the 50 g of water if all the energy calculated in (ii) is absorbed by the water. The specific heat capacity of water i