GMSS Prelim P2 Ans

Candidate Name Class Index Number _______________________________________________________________ PHYSICS Paper 2 Physics 6091/02 Sec 4 Express Additional materials : NIL 1 hour 45 minutes 13 August 2024 READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs Do not use staples, paper clips, highlighters, 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. You are advised to show all your working in a clear and orderly manner. 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. Acceleration due to gravity, g, is assumed to be 10 m/s2 unless otherwise specified. For Examiner’s Use Section A /70 Section B /10 Total /80 This document consists of 19 printed pages and 1 blank page. [Turn over Geylang Methodist School (Secondary) Preliminary Examination 2024 ANSWERS

2 GMS(S)/Physics/P2/Prelim/2024/4E Section A Answer all questions. 1 Fig. 1.1 shows the velocity-time graph for the first 80 s after an object is dropped from rest at a height of 2000 m above the ground. Fig. 1.1 The object has a mass of 9.0 kg. (a) State the acceleration of the object at 0 s. acceleration = ……………10 m/s2………… [1] (b) Describe the motion from 0 to 80 s. From 0 to 40 s, object is moving downwards with a decreasing acceleration. [1] From 40 to 60 s, object is moving downwards with a constant velocity of 40 m/s. [1] From 60 to 80 s, object is moving upwards [1] with a decreasing deceleration [1] (c) Describe the energy transfer when the object is travelling at terminal velocity. Energy is transferred from the gravitational potential store of the object [1] to the internal stores of the surrounding and the object. [1] (d) Calculate the maximum possible air resistance acting on the object when the object is falling at terminal velocity. Max air resistance = weight = 9.0 x 10 = 90 N [1] Maximum air resistance = ……………….………[1]

3 GMS(S)/Physics/P2/Prelim/2024/4E 2 A 7.0 kg picture frame is being suspended from a nail by a string. The string forms two segments L1 and L2, as shown in the Fig. 2.1. L1 and L2 make an angle of 35° and 60° with the vertical respectively. Fig. 2.1 (a) In the space below, draw a vector diagram to determine the tension forces in segments L1 and L2. Specify the scale used. diagram [1], scale [1] scale = ………………… force in L1 = 61 N [1]…, force in L2 = 40 N [1] (b) State the magnitude and direction of the force by the nail, on the string. 70 N [1] Vertically up [1] (c) The picture frame was adjusted such that both segments of the string make an angle of 44.5° with the vertical. State the changes to the tensions in segment L1 and L2 and how their magnitudes compare. Tension in L1 decreases and tension in L2 increases. [1] Their magnitudes are equal. [1]

4 GMS(S)/Physics/P2/Prelim/2024/4E 3 Fig. 3.1 shows a man holding a 0.20 N object in his hand with his forearm in a horizontal position. He can support the object in this position because the flexor muscle exerts a force, FM vertically upward on the forearm. The man's forearm weighs 22 N and its centre of gravity (C.G.) is indicated in the diagram. The forearm can rotate about the elbow joint. Fig. 3.1 (a) Calculate the value of FM. Taking moment about the elbow joint, Sum of anti-clockwise moment = sum of clockwise moment FM x 0.051 = 22 x (0.089 + 0.051) + 0.2 x 0.330 [1] FM = 61.6863 N ≈ 61.7 N (3sf) [1] FM = …………. [2] (b) To keep the forearm in the horizontal equilibrium position, the upper arm bone exerts a force at the elbow joint. Determine the magnitude and direction of this force. Sum of upward forces = sum of downward forces 61.6863 = 22 + 0.2 + F [1] F = 39.5 N (3sf) [1] direction is downwards [1] magnitude = ………………………. direction = ……………….……[3]

5 GMS(S)/Physics/P2/Prelim/2024/4E (c) Explain why the force in (b) is not considered in the calculation in (a). The line of action of this force passes through the pivot so its perpendicular distance from pivot is zero / its moment about the pivot is zero. …………………………………………………………………………………………..…[1] 4 Fig. 4.1 shows two vertical tubes P and Q, each closed at the upper end. The pressure in the space above the mercury meniscus in tube P is 16800 Pa. The pressure in the space above the mercury meniscus in tube Q is unknown. Fig. 4.1 Take the density of mercury to be 13600 kg/m3. (a) Using the information provided, calculate (i) the atmospheric pressure; 𝑃atm =hρg +𝑃P =(0.70 m)(13600 kg m-3)(10 N kg-1)+16800 Pa [1] =112000 Pa [1] atmospheric pressure = ……………………………. [2]

6 GMS(S)/Physics/P2/Prelim/2024/4E (ii) the pressure in the space above the mercury meniscus in tube Q. 𝑃atm = hρg +𝑃Q 112000 Pa=(0.55 m)(13600 kg m-3)(10 N kg-1)+𝑃Q [1] 𝑃Q = 37200 Pa [1] pressure = ……………………………. [2] (b) Due to a small knock, tube Q is slightly shifted and ends up at an angle 15° to the vertical, as shown in Fig. 4.2. [1] Fig. 4.2 On Fig. 4.2, draw the new level of the mercury meniscus in tube Q, and explain your answer. Liquid pressure depends only on the vertical height of the liquid column above it and not the geometry of the liquid column. [1] ………………………………………………………………………………………………... ………………………………………………………………………………………………... …………………………………………………………………………………………..…[2]

7 GMS(S)/Physics/P2/Prelim/2024/4E 5 Fig. 5.1 shows the structure of a water cooler that supplies cold water. Fig. 5.1 (a) In the refrigerator unit, a coolant is pumped through the copper pipe. Explain how energy is transferred from the water to the coolant in the pipe. Energy is transferred from the water internal store to the copper pipe internal store by conduction [1] and then from the copper pipe internal store to the coolant internal store by conduction. [1] (b) Describe how the entire tank of water is cooled. The water near the copper pipe is cooled, it contracts, becomes denser and sinks to the bottom of the tank. [1] The warmer water at the bottom, being less dense rises to top to be cooled by the refrigerator unit. This sets up a convection current in the tank. [1] (c) Explain how the polished aluminium tank helps to keep the water cold. The polished aluminum tank is good reflector / poor absorber of infra-red radiation. It reduces energy gain from the surrounding by infra-red radiation. [1]

8 GMS(S)/Physics/P2/Prelim/2024/4E 6 Fig. 6.1 shows the equilibrium positions of some particles in a medium at time t = 0 s. When a longitudinal wave travels through this medium, the displacements of these particles at time t = 1 s are shown in the displacement - position graph (Fig. 6.2). [1] (a) Mark the positions of the particles A – J at the time t = 1 s in the space provided in Fig. 6.3 with reference to the displacement - position graph shown in Fig. 6.2. [1] (b) With reference to your answer to (a) which particle(s) is/are at the (i) centre of compression, particle(s) C and G [1] (ii) centre of rarefaction. particle(s) A, E and I [