NJC 2022 SH1 Promo Paper 2 Qn

1 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 30 September 2020 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 / 9 2 / 6 3 / 6 4 / 8 5 / 10 6 / 10 7 / 15 8 / 16 Total (80m) This document consists of xx printed pages and x blank page.

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4 Answer all the questions in the spaces provided. 1 (a) (i) Distinguish between random and systematic error. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… [3] (ii) Explain why using a graph a nd drawing line of best fit for the different points will reduce the random error. ……………………………………………………………………………………………… ……………………………………………………………………………………………… [1] (b) A ball approaches a ramp with an inclination of 30°. It hits the surface of the ramp at a speed of 5.0 m s −1 at 45° to the normal and bounces off with a speed of 5.0 m s−1 as shown in Fig. 1.1. Fig. 1.1 Determine the change in velocity of the ball. magnitude of change in velocity = ……………………… m s−1 [2] direction of change in velocity is ……………………… ° with respect to the horizontal [1]

5 (c) A physical equation is of the form −= 3 12()r P PQk L where k is a constant, r = (1.55  0.03) mm, P1 = (125  1) kPa, P2 = (100  1) kPa, L = (120  5) m. Determine the fractional uncertainty of Q? fractional uncertainty of Q = ……………………… [2] [Total: 9]

6 2 Popcorn is produced in a shallow pan. One piece of popcorn is projected out of the pan from the base of the pan. Fig. 2.1 shows the trajectory of this piece of popcorn. Fig. 2.1 The piece of popcorn reaches a maximum height of 56.0 cm above the base of the pan. You may assume air resistance is negligible. (a) (i) Show that the vertical component uv of the initial velocity of the piece of popcorn is about 3.3 m s-1. [1] (ii) The piece of popcorn lands at the same level as its starting point in the pan at a horizontal distance of 1.20 m from its starting point. Show that the magnitude of the initial velocity u of the popcorn is about 3.8 m s-1. [3]

7 (b) A microphone placed near the pan recorded the sound emitted as the piece of popcorn was produced. Fig. 2.2 shows how the loudness of the popping sound varied with time. Fig. 2.2 Determine the average acceleration of the popcorn as it pops. acceleration = …………………… m s-2 [2] [Total: 6]

8 3 (a) When a body is submerged in a fluid, it experiences an upthrust due to the fluid. Explain the origin of upthrust. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… [2] (b) A block of concrete M, of mass 950 kg and density 4750 kg m-3 is held in equilibrium by a vertical cable BE. The block is fully immersed in water of density 1000 kg m-3. Cable BE is attached to a uniform rigid beam AB which is freely hinged to the ground at A and held by another cable CD. The beam makes an angle of 58° with the ground. The angle between cable CD and the beam is 26°. Fig. 3.1 shows the arrangement. The beam AB has mass 80.0 kg. The mid-point of the beam is D. (i) Show the tension in the cable BE is about 7360 N. [2] A B D C M water, density 1000 kg m-3 E Fig. 3.1 beam 260 580

9 (ii) Determine the tension in cable CD. tension = …………………… N [2] [Total: 6] 4 A ball slides without friction around the loop -the-loop apparatus of radius R as shown in Fig. 4.1. It starts from rest at point A at a height H above the bottom of the loop. The radius of the loop, R, is 0.40 m and the ball has a mass of 0.10 kg. (a) (i) Draw a free-body diagram of the sphere when it reaches the highest point C. Label your forces clearly in the diagram below. [2] Fig. 4.1 R A C H

10 (ii) Calculate the minimum speed required at the highest point C for the ball to remain in contact with the track. minimum speed = …………………..m s-1 [2] (iii) Hence, determine the minimum value of H so that the ball will always remain in contact with the track. minimum value of H = ………………..m [2] (b) If the ball is instead moving at 4.0 m s-1 at the highest point C of the loop, calculate the force exerted by the track on the ball. force = ………………….N [2] [Total: 8]