NJC 2021 SH1 Promo P2 V3 (questions only)

[Turn over NATIONAL JUNIOR COLLEGE SENIOR HIGH 1 PROMOTIONAL EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 2 Structured Questions Candidate answers on the Question Paper. No Additional Materials are required. 9749/02 29 September 2021 2 hours READ THE INSTRUCTION FIRST Write your subject class, registration number and name on all the work you hand in. 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. 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. For Examiner’s Use 1 / 6 2 / 7 3 / 7 4 / 7 5 / 13 6 / 10 7 / 10 8 / 20 Total (80m) This document contains 23 printed pages and 01 blank page.

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4 1 A small wooden block is held stationary on a rough slope at a distance of 2.0 m from the bottom of the slope. At time t = 0, it is projected up the slope with an initial speed of 5.0 m s-1 as shown in Fig. 1.1. The deceleration of the block is 6.0 m s-2. (a) Show that the distance travelled by the block, relative to its initial position at t = 0, before it comes to rest momentarily at the top of the slope is 2.1 m. [1] (b) Determine the time taken for the block to travel to the top of the slope. time = ...................... s [1] (c) After reaching the top of the slope, the block starts to slide down with an acceleration of 3.8 m s-2. Determine (i) the time taken for the block to travel from the top of the slope to the bottom of the slope. t = ........................... s [1] (ii) the speed of the block on reaching the bottom of the slope. speed = ................. m s-1 [1] Fig. 1.1

5 [Turn over (d) On Fig. 1.2, sketch the variation with time, of the displacement of the block (relative to the start point) for the entire motion starting from t = 0 to the instant the block reaches the bottom of the slope. Take displacement upslope to be positive. [2] 0 Fig. 1.2 Displacement / m Time / s 2.0 − 2.0

6 2 (a) Derive, from the definitions of pressure and density, the equation for pressure due to a column of liquid is given by =p h g [3]

7 [Turn over (b) Fig. 2.1 shows a simplified catapult used to hurl projectiles a long way. Fig. 2.1 The counterweight is a wooden box full of stones to one end of the uniform beam. The projectile, usually a large rock, is in a sling hanging vertically from other end of the beam. The weight of the sling is negligible. The beam is held horizontal by a rope attached of the frame. The stones and the wooden box in the counterweight have a total mass of 1000 kg, the mass of the beam is 500 kg and the projectile weighs 250 N. Calculate the tension in the rope. Explain your working clearly. tension = ………………………………… N [4]

8 3 (a) Two ma sses, 2.5 kg and 4.5 kg , are connected by an inextensible cord that runs over a frictionless and massless pulley as shown in Fig. 5.1. Both masses are released from rest and they moved a distance of 0.50 m. (a) Determine the final speed of the system after travelling 0.50 m. speed = ..................... m s-1 [3] (b) The power of the engine of a sports car of mass 1500 kg is 200 kW in normal driving mode. It can cruise at speed of 90 km h-1. (i) Show that the force that is delivered by the engine to the car is 8000 N. [2] (ii) When the car suddenly switches to turbocharging mode, the power doubles. Assuming the resistive force remains the same at that instant, determine the acceleration. acceleration = .................... m s-2 [2] 30 2.5 kg 4.5 kg Fig. 5.1

9 [Turn over 4 A circus performer is riding his motorcycle with uniform speed such that its period is 20.0 s in a horizontal circle of radius 83 m on the inner surface of a cylindrical wall, as shown in Fig. 4.1. The orientation of his motorcycle is shown in Fig. 4.2. The two forces acting on the motorcycle -man system are the reaction force R acting at an angle  with the vertical and the weight W. (a) R is the resultant of two forces. They are perpendicular to each other. State the two forces. ..................................................... ............................................................................................. [1] (b) One of forces in (a) points to the left of the Fig 4.2, show that this force is F = 0.835 W [2] (c) Hence, show that the angle  is 39.9 [3] (d) Explain why is it not possible for  to be 90. ....................................................................................................................................................... ................................................................................................................................................... [1] W  R wall 83 m Fig. 4.1 Fig. 4.2

10 5 (a) Define simple harmonic motion. ....................................................................................................................................................... ....................................................................................................................................................... .................................................................................................................................................. [2] (b) Fig. 5.1 shows the variation of amplitude of oscillation of a system with the frequency of an external source. The system is critically damped. (i) State the name of the phenomenon illustrated in Fig. 5.1. .......................................................................................................................................... [1] (ii) Sketch, on Fig. 5.1, the variation of the amplitude with frequency for the same system that is lightly damped. [3] Fig. 5.1