NJC_2025_H2_Physics_Prelim_P3SectionA_QP

[Turn over NATIONAL JUNIOR COLLEGE SENIOR HIGH 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 3 Longer Structured Questions (Section A) Candidate answers on the Question Paper. 9749/03 19 Sep 2025 2 hours No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your subject class, registration number and name in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Section A Answer all questions. You are advised to spend one and a half hours on Section A and half an hour on Section B. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 / 10 2 / 10 3 / 9 4 / 11 5 / 10 6 / 10 Sub- Total / 60 Section B / 20 Total / 80 H

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4 Answer all the questions in the spaces provided. 1 (a) Define gravitational potential at a point. ……………………………………………………………………………………………………………… …………………………………………………………………………………………………………… [1] (b) The Earth may be considered to be an isolated sphere of radius R with its mass M concentrated at its centre. The variation of gravitational potential φ with distance x from the centre of the Earth is shown in Fig. 1.1. Fig. 1.1 The radius R of the Earth is 6.4 × 106 m. (i) Show that the mass M of the Earth is 6.0 × 1024 kg. [2]

5 [Turn over (ii) A meteorite is at rest at infinity. The meteorite travels from infinity towards the Earth. When the meteorite at a distance 2R above the Earth’s surface, calculate 1. the speed of the meteorite, speed = ………………………… m s−1 [3] 2. the acceleration of the meteorite. acceleration = ………………………… m s−2 [2] (iii) In practice, the Earth is not an isolated sphere because it is orbited by the Moon. Suggest how the speed calculated in (ii)1. will change. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] [Total: 10]

6 2 A cylinder that contains a fixed amount of an ideal gas is shown in Fig. 2.1. Fig. 2.1 The cylinder is tightly fitted with a piston, of cross -sectional area A. The piston moves freely in the horizontal direction, trapping the gas within a length x. (a) A gas molecule of mass m travels at a speed of u in the horizontal direction and collides elastically with the piston and the walls of the container. (i) State an expression, in terms of some or all of the symbols def