CGS 2025 Physics P2 MS

This paper consists of 21 printed pages including this cover page. Class: Index No.: Name: Marking Scheme CRESCENT GIRLS’ SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION PHYSICS 6091 / 02 Paper 2 Structured and Free Response 02 September 2025 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, index number and class in the spaces provided at the top of this page and on all separate answer sheets used. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluids. Section A Answer all questions. Write your answers on the spaces provided. Section B Answer one question. Write your answers on the spaces provided. 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.

2 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME Note to markers: 1. Penalty for errors in significant figures – 1 mark for whole paper 2. Penalty for errors in units or missing units – 1 mark per whole question Section A Answer all questions in this section. 1 Two small tugboats are pulling a ship in a harbour. Fig. 1.1 represents the view from above and shows the directions of the forces on the ship. Fig. 1.1 (not to scale) Each of the tugboats is exerting a horizontal force of 49 kN on the ship. (a) By drawing a scaled vector diagram, determine the resultant of these two forces. Label your forces. Answer Marks appropriate scale used (e.g., 1 cm represents 10 kN) B1 correct vector diagram, including direction and labelling M1 90 kN ≤ resultant ≤ 94 kN A1 with units

3 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME (b) The engines of the ship are not operating and the water in the harbour is stationary. The ship is moving at a constant speed in a straight line in the direction of the resultant of the two forces exerted by the tugboats. Explain, in terms of the forces acting, why the ship is moving in a straight line at constant speed. Answer Marks water resistance / drag B1 same magnitude and acts in opposite direction to the resultant of the forces by tugboat B1 no resultant force on the ship B1 (c) Both cables connecting the tugboats and the ship are detached at the same instant. The mass of the ship is 2.4 × 107 kg. Determine the magnitude of the acceleration, and its direction relative to the motion of the ship, at this instant. Answer Marks F = ma 92 × 103 = (2.4 × 107) a a = 3.8 × 107 m s-2 accept 3.83 × 107 m s-2 A1 – allow e.c.f. from (a) direction relative to motion of ship: opposite / 180 A1 magnitude = …………………………………. [ 1] direction relative to motion of the ship = …………………………………. [ 1] [Total: 8 marks]

4 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME 2 Fig. 2.1 shows a man sitting on a chair resting on four legs. Fig. 2.2 shows the same man with his chair tilted backwards slightly. Fig. 2.1 Fig. 2.2 The man has a weight of 650 N and the chair has a weight of 20 N. Each base area of each leg is 5.0 cm2. (a) Calculate the pressure exerted on the floor when the chair is in the position shown in Fig. 2.1. Answer Marks pressure = force / area = (650 + 20) / (4  5.0) = 670 / 20 cm2 OR 670 / (2.0  10-3 m2) C1 - seen 34 N/cm2 accept 33.5 N/cm2; 330 kPa; 335 kPa; 335 kN/m2 A1 – with units pressure = 34 N/cm2 [2] (b) State and explain, without any calculations, how the pressure of the chair on the floor differs in the two positions. Answer Marks Greater/larger pressure in Fig. 2.2 (than in Fig. 2.1) [not accepted: large/big pressure in Fig. 2.2] B1 – comparative answer  Since pressure is force per unit area, with the same weight, the pressure is greater with a smaller contact area in Fig 2.2. B1

5 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME (c) In Fig. 2.2, the chair and man are about to fall over. On Fig. 2.2, draw an “ X” to indicate the position of the centre of gravity of the chair and man. [1] Answer Marks X is marked clearly along the vertical axis of the back legs of the chairs within the 2 horizontal dotted boundaries. B1 (d) The chair and man fall over if the chair is tilted backwards more than in Fig. 2.2. Explain why. Answer Marks  The (combined) centre of gravity is outside the base / legs / chair  Weight acts on left or outside of chair leg B1 Net anticlockwise / unbalanced moment is created causing the chair to tilt backwards. B1 [Total: 7 marks]

6 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME 3 Fig. 3.1 shows the plan of a bedroom and part of the main room of a house . Other parts of the house are not shown. Fig. 3.1 The temperatures of the main room, the bedroom and the outside of the house are shown in Fig. 3.1. Fig. 3.2 shows the thermal energy transfers to the bedroom in one hour. through the door and walls from the main room 60 000 J through the walls from the outside 1 500 000 J through the window 200 000 J Fig. 3.2 (a) State the key process of heat transfer to the bedroom. Answer Marks Heat / thermal conduction (through the walls) B1 (b) Suggest why more thermal energy enters the bedroom from the outside of the house than from the main room. Answer Marks  Larger temperature difference between the bedroom and outside of house OR  Outside of the house is hotter than the main room B1

7 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME (c) Suggest two ways to reduce the different heat transfers into the bedroom through the walls from the outside. Answer Marks Any 2 of following answers  Paint the (exterior) walls white (or light colours).  Make the (exterior) wall surface smooth / shiny  Add insulating material to the (exterior) wall surface.  Double-glaze the walls (any answer that implies the same effect)  Any logic al answer that reduces heat transfer by conduction and/or radiation [not accepted – specific solutions without relating the property that affects rate of heat transfer. E.g., cover walls with foil, vs cover the walls with shiny foil] B1 each (d) An air conditioner is installed in each room to keep the room at the temperatures shown in Fig. 3.1. The air conditioners are installed at the top of each room. Explain how this set-up helps to cool the air in the rooms. Answer Marks Air at the top of the rooms is cooled and becomes denser. B1 Cold air sinks and the warmer air that is less dense rises (from the bottom of the room) B1 Convection current is set up (to continue cooling the room). B1 [Total: 7 marks]

8 ⏹ ⌞ ⌟ 6091/02/CGS/2025 - MARKING SCHEME 4 Both sound and ultrasound are longitudinal waves that travel in solids, liquids and gases. Both consist of compressions and rarefactions. (a) (i) State how sound differs from ultrasound. Answer Marks frequency of sound waves smaller (than ultrasound) OR its frequency is less than 20 kHz (whereas ultrasound has a frequency greater than 20 kHz) B1 (ii) Explain what is meant by a wave and state the direction of vibration of the wave particles in relation to the wave motion. Answer Marks transfer / propagation of energy by vibrating (medium) particles B1 with no net transfer of (medium) particles B1 vibrations of (medium) particles parallel to direction of energy transfer / propagation in the longitudinal wave (no comparison needed) B1 (b) Fig. 4.1 represents a longitudinal wave of frequency 25 kHz traveling in oil. Fig. 4.1 (full scale) (i) On Fig. 4.1, 1. mark one point at the centre of a rarefa