2020 RI Prelims H2 Phy Paper 2 QP

This document consists of 24 printed pages. © Raffles Institution 9749/02 [Turn over Centre Number Index Number Name Class S3016 RAFFLES INSTITUTION 2020 Preliminary Examination PHYSICS Higher 2 Paper 2 Structured Questions 9749/02 16 September 2020 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your index number, name and class in the spaces at the top of this page. Write in dark blue or black pen in the spaces provided in this booklet. You may use 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. Answer 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 / 8 3 / 8 4 / 12 5 / 12 6 / 8 7 / 24 Deduction Total / 80

2 © Raffles Institution 9749/02 Data speed of light in free space c  3.00 × 108 m s1 permeability of free space 0  4   107 H m1 permittivity of free space 0  8.85 × 10 12 F m1  (1/(36 )) × 109 F m1 elementary charge e  1.60 × 10 19 C the Planck constant h  6.63 × 10 34 J s unified atomic mass constant u  1.66 × 10 27 kg rest mass of electron me  9.11 × 10 31 kg rest mass of proton mp  1.67 × 10 27 kg molar gas constant R  8.31 J K 1 mol1 the Avogadro constant NA  6.02 × 10 23 mol1 the Boltzmann constant k  1.38 × 10 23 J K1 gravitational constant G  6.67 × 10 11 N m2 kg2 acceleration of free fall g  9.81 m s 2   Formulae uniformly accelerated motion s  21 2ut at 2v  2 2ua s work done on/by a gas W  p V hydrostatic pressure p  ρgh gravitational potential   Gm r temperature T/K  / C 273.15T  pressure of an ideal gas p  21 3 Nm cV mean translational kinetic energy of an ideal gas molecule E  3 2 kT   displacement of particle in s.h.m. x  0 sinx t velocity of particle in s.h.m. v  0 cosvt  22 0x x  electric current I  Anvq resistors in series R  12 ...RR resistors in parallel 1/ R  121 1 ...RR electric potential V  4 Q r alternating current/voltage x  0 sinx t magnetic flux density due to a long straight wire B  0 2 d   I magnetic flux density due to a flat circular coil B  0 2 N r  I magnetic flux density due to a long solenoid B  0n I radioactive decay x   0 expx t decay constant   1 2 ln2 t

3 © Raffles Institution 9749/02 [Turn over Answer all the questions in the spaces provided. 1 (a) A projectile, at ground level, is launched with an initial velocity u at an angle  to the horizontal as shown in Fig. 1.1. Fig. 1.1 Ignoring the effects of air resistance, show that the time t 0 taken by the projectile to land on the ground is given by 0 2s i nut g  . Explain your working. [2] (b) Fig. 1.2 shows a cart moving with constant velocity v in front of the projectile launcher. A projectile is launched with velocity 135 m su  at an angle 23  . At this instant, the back of the cart is 45 m from the position of launch. Fig. 1.2 35 m s1 23  v cart projectile 45 m ground u  projectile ground

4 © Raffles Institution 9749/02 (i) Ignoring the effects of air resistance, 1. Determine the velocity v of the cart such that the projectile will land just behind it. v = m s1 [3] 2. On Fig. 1.3, sketch the variation with time t of the kinetic energy EK of the projectile from the time it was launched to the time it just lands behind the cart. Include all relevant numerical values on the horizontal axis. Fi g. 1.3 [2] (ii) Suggest how the projectile should be launched such that it will still land just behind the cart, if the effects of air resistance on the projectile are not negligible. [1] t / s EK 0

5 © Raffles Institution 9749/02 [Turn over 2 Fig. 2.1 shows a crane being used to lift and lower a load of mass 300 kg. The load at point B is attached to point A of the jib using a cable. Another supporting cable attached at point C s upports the far end of the jib at point A. The supporting cable makes an angle of 25 with the jib at point A. The nearer end of the jib is connected to the cab at point D. The mass of the jib is 2400 kg and the mass of the cab is 16000 kg. Their centres of mass are at their mid-points E and F respectively. The masses of the hook at point B and the cables are ne gligible. Fig. 2.1 (a) When the load is lowered with a deceleration of 1.0 m s –2, (i) show that the tension in the cable AB is 3240 N, [1] (ii) calculate the corresponding tension in the supporting cable AC. tension in AC = N [2] A supporting cable 5.0 m F E jib 8.0 m 25 cab load B C D 10.0 m

6 © Raffles Institution 9749/02 (b) For the jib in the position shown in Fig. 2.1, there is a maximum load which will just topple the crane. (i) On Fig. 2.1, label G, the point about which the crane will topple. [1] (ii) Determine the maximum load which will just topple the crane. maximum load = N [2] (c) The load is a rectangular slab of concrete. Fi g. 2.2 shows how the slab of concrete is hooked to cable AB of the jib. Fig. 2.2 Explain why the crane is more likely to topple on a windy day when carrying this slab of concrete. [2] cable AB slab of concrete to jib

7 © Raffles Institution 9749/02 [Turn over 3 A small ball of mass 0.30 kg is attached to one end of a light inelastic string. The other end C of the string is fixed. The ball is made to rotate about C in a vertical circle of radius 65 cm as shown in Fig. 3.1. Fig. 3.1 The angular speed of the ball is gradually increa sed from zero until the string snaps. This happens when the tension in the string is 16 N. (a) The string is observed to snap when the ball is vertically below C. (i) On Fig. 3.1, sketch the path of the ball after the string snaps. [1] (ii) Calculate the angular speed 1 of the ball at the instant the string snaps. 1 = rad s1 [2] C ball 65 cm string

8 © Raffles Institution 9749/02 (b) Another experiment is carried out with anot her set of identical string and ball. The ball is rotated in a horizontal circ le, with the string inclined at an angle    to the vertical, as shown in Fig. 3.2. Fig. 3.2 The angular speed of the ball is gradually in creased from zero and the ball is observed to rise to a higher horizontal plane. The string snaps when the angular speed is increased to 2 . (i) In terms of the forces acting on the ball, explain the observation that the ball rises to a higher horizontal plane when the angular speed is increased. [3] (ii) Explain, using relevant equations or otherwise, whether 2 is larger or smaller than 1 in (a)(ii) when the string snaps. [2] ball C  string

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