NJC 2025 H2 Physics Prelim P2 QP

[Turn over NATIONAL JUNIOR COLLEGE SENIOR HIGH 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 2 Structured Questions Candidate answers on the Question Paper. 9749/02 2 Sep 2025 2 hours No Additional Materials are required. READ THE INSTRUCTION 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 or graphs. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Answers all questions. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 8 2 / 10 3 / 6 4 / 6 5 / 10 6 / 10 7 / 10 8 / 20 Total / 80 H

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4 Answer all the questions in the spaces provided. 1 A small pellet of mass 8.00 × 10–3 kg is projected at an angle 𝜃 above the horizontal, as shown in Fig.1.1. The speed of projection is u. The pellet reaches a maximum height of 10.0 m and travels at a speed of 5.00 m s–1 at maximum height. (a) Air resistance is negligible. (i) Using energy conservation, show that the initial speed of projection is 14.9 m s–1. [1] (ii) Calculate the angle of projection 𝜃. 𝜃 = …………….……. ° [2] (iii) Determine the time taken by the pellet from launch to impact with the ground. 10.0 m Ground Fig. 1.1 q

5 [Turn over time = …………………. s [2] (iv) Determine the average rate of change of momentum of the pellet from the instant of projection to the instant before it hits the ground. rate of change of momentum = ……………… N [1] (b) Fig. 1.2. shows part of the graph (up to the maximum height) of the variation with time of the vertical displacement of the pellet when air resistance is not negligible. Complete the graph from the maximum height to the instant the pellet hits the ground. Numerical values are not required. [2] [Total: 8] 0 Vertical displacement time Fig. 1.2

6 2 (a) Momentum is conserved when two objects collide. State the condition under which momentum is conserved. ……………………………………………………………………………………………………………… …………………………………………………………………………………………………………….[1] (b) Fig. 2.1 shows the variation with time of the momentum of two colliding trucks A and B. Fig. 2.1 The masses of trucks A and B are 2000 kg and 4000 kg respectively. The period of collision is between 1.5 s and 3.0 s. (i) Calculate the force acting on truck B during the collision force = ……………. N [2] (ii) Explain using Newton’s laws, the relationship between the gradients of both graphs during the collision. ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..………………

7 [Turn over ………………………………………………………………………………………..……………[2] (iii) Using the concepts of impulse and momentum, explain why the total momentum of the two trucks is conserved during collision. ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………… ………………………………………………………………………………………..……………[2] (iv) Calculate the change in the total kinetic energy of the trucks before and after the collision. State the type of collision. change in kinetic energy = ………………………… J [2] type of collision: ……………………………….………[1] [Total: 10]

8 3 Fig. 3.1 shows a wheel that is being pulled over a kerb of height 0.080 m by a horizontal force F. The weight of the wheel is 700 N and the wheel has a radius of 0.60 m. At the instant shown, the wheel just loses contact with the ground at G. (a) Show that 𝜃 is 30°. [1] (b) On Fig. 3.1, draw an arrow to represent the contact force exerted on the wheel at P. [1] (c) Show that the minimum value of F is 190 N. [1] (d) Hence, determine the magnitude of the contact force at P. Fig. 3.1 (Not to scale) 700 N 0.080 m q F G P

9 [Turn over magnitude = ……………….. N [3] [Total: 6] 4 Binary star systems, consisting of two stars orbiting around each other, are very common. Fig. 4.1 shows two stars of mass M and 2M in circular orbits about point C. The centre-to-centre separation between the two stars is 3.0 × 1012 m. Both stars have the same orbital period, and they are always located on opposite sides of C. (a) Explain how the gravitational force acting on one star is equal to the gravitational force acting on the other star. ………...…………………………………………………………………………………….……………… ……….…………………………………………………………………………………………………..[1] (b) The orbital radius of 𝑀 is 𝑟1 and the orbital radius of 2M is 𝑟2. By considering the magnitude of the centripetal forces acting on the two stars, show that 𝑟1 𝑟2 = 2 Fig. 4.1 C

10 [1] (c) Hence, or otherwise, determine the value of 𝑟1. 𝑟1 = ……………………… m [2] (d) M is 2.0 × 1030 kg. Determine the orbital period T of the stars. T = ………………….. s [2]