2023 CHS Phy Prelims P2

Name: Index Number: Class: CATHOLIC HIGH SCHOOL Preliminary Examination Secondary 4 (O-Level Programme) PHYSICS 6091/02 Paper 2 Theory 25 Aug 2023 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. Write in dark blue or black link. You may use a HB pencil for any diagrams or graphs. Do not use paper clips, glue or correction fluid. Section A Answer all questions. Section B Answer all questions. Question 12 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. For examiner’s use only: Section A / 50 Section B / 30 Total / 80 Overall Marks % Paper 1 40 30% Paper 2A 50 50% Paper 2B 30 Paper 3 40 20% This document consists of 26 printed pages. 50  s.f.  formula Paper 2A

2 Section A Answer all the questions in this section. 1 A rock of mass 7.5 kg is projected vertically upwards from the surface of planet X. The rock leaves the surface of planet X with a velocity of 4.0 m / s at time t = 0 s. The variation of velocity v with time t of the rock is shown in Fig. 1.1. Fig. 1.1 Assume that the air resistance acting on the rock is zero. (a) (i) Determine the height of the rock above the surface of planet X at time t = 2.5 s. height = [2] (ii) Determine the deceleration of the rock. deceleration = [2]

3 (b) The rock is now thrown vertically upwards on another planet Y with an initial velocity of 4.0 m / s. Planet Y has the same gravitational field strength as planet X. Air resistance acting on the rock is not negligible. (i) The resultant force acting on the rock is downwards and decreasing as it travels upwards. On Fig. 1.1 , draw the velocity-time graph of the rock on planet Y until it reaches the highest point. [1] (ii) Determine the magnitude of air resistance when the rock is travelling at terminal velocity at planet Y. air resistance = [1]

4 2 Fig. 2.1 shows a rocket about to be launched. Fig. 2.1 The total mass of the rocket and its full load of fuel is 2.8 × 106 kg. The motor of the rocket provides a constant force. The vertical acceleration of the rocket immediately after lift-off is 1.4 m / s2. The gravitational field strength of Earth is 10 N / kg. (a) Calculate the constant force provided by the motor of the rocket. constant force = [3] (b) Suggest two reasons why the acceleration of the rocket increases as it rises above the Earth’s surface. [2]

5 3 A rod XY is pivoted at point P, as shown in Fig. 3.1. Fig. 3.1 The rod has a length of 4.0 m and its weight is 44 N. The centre of gravity of the rod is 1.7 m from end X of the rod. Point P is 1.1 m from end X. A sphere hangs by a wire from end Y of the rod and is immersed in a liquid in a container. The weight of the sphere is 3.0 N. The weight of the wire is negligible. A force F is applied vertically downwards at end X so that the horizontal rod is in equilibrium. (a) (i) State what is meant by the centre of gravity of an object. [1] (ii) Explain whether the rod XY is a uniform rod. [1] F 44 N sphere wire container liquid 4.0 m 1.7 m 1.1 m 3.0 N X Y

6 (b) The liquid exerts an upward force of magnitude 2.5 N on the sphere which reduces the force exerted by the sphere on the rod. Determine force F. force F = [2] (c) The sphere is removed from the container with liquid as shown in Fig. 3.2. The magnitude of force F remains unchanged. Fig. 3.2 Explain how pivot P should be shifted for rod XY to remain in equilibrium. [2]

7 4 Two physical properties are being considered for use to construct a temperature scale of a thermometer. They are the volume of water and the pressure of a fixed mass of gas at constant volume. Table 4.1 shows the values of the physical quantities at different temperatures. Table 4.1 temperature / °C volume of water / cm3 pressure of gas / Pa 0.0 3.47 2270 8.0 3.47 2340 30.0 3.49 2520 50.0 3.52 2690 80.0 3.58 2940 100.0 3.63 3100 (a) Using Table 4.1, suggest why the volume of water is not an appropriate choice to construct the Celsius scale of a thermometer. [2] (b) Fig. 4.2 shows a constant volume gas thermometer that measures temperature by using the variation in the pressure of a gas. Fig. 4.2 As the temperature of the gas increases, the mercury level at A will decrease initially. The volume of the gas in the flask is then kept constant by raising or lowering the reservoir of mercury in B to keep the mercury level at A constant. mercury h gas round bottom flask A B

8 (i) Using ideas about molecules, explain why the mercury level at A decreases initially as the temperature of the gas increases. [3] (ii) The round bottom flask is immersed into a container of hot water. State and describe the main process of heat transfer between the flask and the gas. [2]

9 5 In an experiment to find the specific latent heat of vaporisation of water, the readings in Table 5.1 were taken. Table 5.1 θ initial temperature of water 35 °C m1 mass of water at 100 °C, before boiling starts 120 g m2 mass of water at 100 °C, after boiling finishes 80 g V potential difference across the heater 12 V I current through the heater 2.0 A t1 time that the heater was supplying energy to raise the temperature of water from 35 °C to 100 °C 2700 s t2 time that the heater was supplying energy during boiling 3750 s (a) The total mass of water does not change as the temperature of water is raised from 35 °C to 100 °C. Calculate the specific latent heat of vaporisation of water from the readings in Table 5.1. specific latent heat of vaporisation = [3] (b) Explain, in terms of the energy of molecules, why the specific latent heat of vaporisation of water has a high value. [1]

10 6 A water wave travels through a ripple tank from left to right. Fig. 6.1 shows the variation of the displacement dA of a point A on the water wave with time. Fig. 6.1 Fig. 6.2 shows a section of the water wave travel ling through the ripple tank at time t = 0 s. A point on the water wave B is as indicated. Fig. 6.2 (a) Determine the frequency of the wave shown in Fig. 6.1. frequency = [2] (b) On Fig. 6.1, draw the displacement-time graph for the water particle at point B for one period. [1] dA / cm 6.0 4.0 2.0 0.0 -6.0 -4.0 -2.0 B direction of water wave