2020 RI Prelims H2 Phy Paper 3 Sect A QP

This document consists of 18 printed pages. © Raffles Institution 9749/03 [Turn over Centre Number Index Number Name Class S3016 RAFFLES INSTITUTION 2020 Preliminary Examination PHYSICS Higher 2 Paper 3 Longer Structured Questions 9749/03 23 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. Section A Answer all questions. Section B Answer one question only and circle the question number on the cover page. 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. *This booklet only contains Section A. For Examiner’s Use Section A 1 / 8 2 / 10 3 / 10 4 / 10 5 / 10 6 / 12 Section B (circle 1 question) 7 / 20 8 / 20 Deduction Total / 80

2 © Raffles Institution 9749/03 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 expxt  decay constant   1 2 ln2 t

3 © Raffles Institution 9749/03 [Turn over Section A Answer all the questions in this Section in the spaces provided. 1 Body A of mass m and speed u1 makes an elastic head-on collision with body B of mass 2 m and speed u2 as shown in Fig. 1.1. Fig. 1.1 (a) Describe the subsequent motion of the two bodies knowing that (i) the collision is head-on, [1] (ii) the collision is elastic. [1] (b) Given that the speeds u1 is 4.0 m s–1 and u2 is 2.0 m s–1, determine the velocity of each body after the collision. velocity of A = m s –1 velocity of B = m s –1 [4] u1 u2 A B

4 © Raffles Institution 9749/03 (c) Bodies A and B are steel ball bearings. If their motions occur in a vertical plane as shown in Fig. 1.2, with u1 directed downwards and u2 upwards, the principle of conservation of momentum can still be applied in analysing the collision between them. Fig. 1.3 shows a similar scenario, but with a piece of styrofoam of negligible mass attached to the top of body B. Fig. 1.2 Fig. 1.3 Explain why the principle of conservati on of momentum cannot be applied in analysing the collision in Fig. 1.3. [2] u1 u2 A B u1 u2 A B styrofoam

5 © Raffles Institution 9749/03 [Turn over 2 (a) Fig. 2.1 also shows two equipotential lines around Star X. The gravitational potentials at points Q and R are 12 13.0 10 J kg  and 12 11.0 10 J kg  respectively.                       Fig. 2.1 (i) Explain why the gravitational potential at a point is always negative. [2] (ii) The gravitational potential at point Q which is 70.98 10 km from the centre of Star X is 12 13.0 10 J kg  . What is meant by the above statement? [1] R Q Star X

6 © Raffles Institution 9749/03 (iii) Calculate the distance from the centre of star X to point R. distance = km [2] (iv) Calculate the work done by an external force in bringing a body of mass 1200 kg from points R to Q. work done = J [2] (b) Star Y forms part of a binary star system with Star Z. Bo th stars orbit about a common centre C as shown in Fig. 2.2. Fig. 2.2 x1 x2 Star Y Star Z C

7 © Raffles Institution 9749/03 [Turn over The following data are given: mass of Star Y 302.62 10 kg mass of Star Z 281.45 10 kg (i) The orbital radii of Stars Y and Z are x1 and x2 respectively. Determine the ratio 2 1 x x . 2 1 x x = [2] (ii) Explain why both stars must rotate with the same angular velocity about C. [1]

8 © Raffles Institution 9749/03 3 (a) Gravitational fields, electric fields and magnetic fields are examples of fields of force. State the direction of the force acting on the body with respect to the field it is in for each of the following scenarios. (i) The Moon in the gravitational field of the Earth. [1] (ii) An electron released from rest in the electric field of a positive point charge. [1] (iii) An electron moving at an angle to a uniform magnetic field. [1] (b) An isolated point charge S in a vacuum produces electric potential V at distance r from S. Fig. 3.1 shows the variation with r of V. Fig. 3.1 1.0 2.0 3.0 4.0 5.0 6.0 r / cm 0 0 100 400 500 300 200 800 700 600 V / V

9 © Raffles Institution 9749/03 [Turn over (i) Show that the charge of S is 108.7 10 C . [1] (ii) An electron is projected radially from 2.0 cmr  with a speed of 618.4 10 m s  away from S. Using Fig. 3.1, determine the maximum distance of the electron from S. maximum distance = cm [2] (iii) A negative point charge T is now placed at a fixed distance 6.0 cmr  from S. The charge of T is 108.7 10 C . 1. Sketch on Fig. 3.3, the variation with distance r from S of the electric force F on an electron when it is between S and T. Fi g. 3.3 [2] 0 1.0 2.0 3.0 4.0 5.0 6.0 r / cm F

10 © Raffles Institution 9749/03 2. If the electron in (b)(ii) is again projected from 2.0 cmr  with the same speed towards T, explain how the maximum distance of the electron from S will change. [2]