2013 PJC H2 Physics P2

2013/PJC/PHYSICS/9646 [Turn over PIONEER JUNIOR COLLEGE JC2 Preliminary Examination PHYSICS 9646/02 Higher 2 Paper 2 Structured Questions 20 September 2013 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer 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. This document consists of 21 printed pages. Name Class Index Number For Examiner’s Use 1 / 10 2 / 8 3 / 7 4 / 10 5 / 9 6 / 16 7 / 12 Total / 72

2 2013/PJC/PHYSICS/9646 Data speed of light in free space, 81000.3 c ms–1 permeability of free space, 7 0 104   Hm–1 permittivity of free space, 12 0 1085.8  Fm–1    910361   Fm–1 elementary charge, 191060.1 e C the Planck constant, 341063.6 h Js unified atomic mass constant, 271066.1 u kg rest mass of electron, 311011.9 em kg rest mass of proton, 271067.1 pm kg molar gas constant, 31.8R JK–1 mol–1 the Avogadro constant, 231002.6 AN mol–1 the Boltzmann constant, 231038.1 k JK–1 gravitational constant, 111067.6 G Nm2 kg–2 acceleration of free fall, 81 .9g ms–2

3 2013/PJC/PHYSICS/9646 [Turn over Formulae uniformly accelerated motion, 2 2 1 atuts  asuv 222  work done on/by a gas, VpW  hydrostatic pressure, ghp  gravitational potential, r Gm displacement of particle in s.h.m., txx sin0 velocity of particle in s.h.m., tvv cos0 22 0 xx   mean kinetic energy of a molecule kTE 2 3 of an ideal gas, resistors in series, ... 21  RRR resistors in parallel, ... /1/1/1 21  RRR electric potential, r QV 04 alternating current/voltage, txx sin0 transmission coefficient,  kdT 2exp  where   2 28 h EUmk   radioactive decay, ) exp( 0 txx  decay constant, 2 1 693.0 t

4 2013/PJC/PHYSICS/9646 1 In a nuclear reactor, a fast moving neutron with initial speed u1 makes a head-on elastic collision with a stationary nucleus of carbon-12 which has a mass 12 times that of the neutron. The speeds of the neutron and the carbon nucleus after the collision are v1 and v2 respectively. (a) What is meant by a head-on elastic collision? .............................................................................................................................. ......... .............................................................................................................................. ......... .............................................................................................................................. ......... .............................................................................................................................. ... [2] (b) (i) State the principle of conservation of linear momentum. .................................................................................................................................. ............................................................................................................................. ..... ............................................................................................................................ [1] (ii) Determine the ratio of the final speed of the neutron v1 to its initial speed u1. ratio = ........................................ [3]

5 2013/PJC/PHYSICS/9646 [Turn over (c) Hence determine the fraction of the kinetic energy of the neutron that is transferred to the carbon nucleus. fraction = ........................................ [2] (d) In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons. Explain which would make a better neutron moderator, carbon-12 or neutron. .............................................................................................................................. ......... .............................................................................................................................. ... [2]

6 2013/PJC/PHYSICS/9646 2 (a) Starting from the definition of work, deduce the change in the gravitational potential energy of a mass m, when moved a distance h upwards against a gravitational field of field strength g. [3] (b) A catapult consists of two strands of rubber that obeys Hooke’s law. Each strand has original length of 0.200 m and each will stretch by 0.100 m when under a tension of 50 N. A mass of 0.060 kg is projected vertically upwards from the catapult after each strand has been extended to a length of 0.350 m. (i) Calculate the energy stored in the stretched catapult. energy stored = ........................................ J [3] (ii) Determine the maximum height attained by the stone if air resistance is negligible. maximum height = ........................................ m [2]

7 2013/PJC/PHYSICS/9646 [Turn over 3 A vertical peg is fixed to the rim of a horizontal turntable of radius r = 15.0 cm, rotating with a constant angular speed  = 4.0 rad s1, as shown in Fig. 3.1. Fig. 3.1 Parallel light is incident on the turntable so that the shadow of the peg is observed on a screen, which is normal to the incident light. At time t = 0, θ = 0 and the shadow of the peg is seen at P. At some time t, the shadow is seen at Q. (a) (i) Write down an expression for x in terms of , r and t, where x is the distance PQ. [1] parallel light peg Q P θ  r screen turntable

8 2013/PJC/PHYSICS/9646 (ii) Hence, prove that the shadow on the screen executes simple harmonic motion. [2] (b) Calculate the speed of the shadow on the screen at a displacement of 7.5 cm above P. speed = ........................................ m s1 [2] (c) Calculate the maximum acceleration of the shadow. maximum acceleration = ........................................ m s2 [2]

9 2013/PJC/PHYSICS/9646 [Turn over 4 Two small charged metal spheres A and B are situated in a vacuum. The distance between the centres of the spheres is 12.0 cm, as shown in Fig. 4.1. Fig. 4.1 The charge on each sphere may be assumed to be a point charge at the centre of the sphere. Point P is a movable point that lies on the line joining the centres of the spheres and is distance x from the centre of sphere A. The variation with distance x of the electric field strength E at point P is shown in Fig. 4.2. Fig. 4.2 sphere A sphere B x 12.0 cm P x / cm E / 106 N C−1

10 2013/PJC/PHYSICS/9646 (a) State the evidence provided by Fig. 4.2 that the spheres are conductors. …............................................................................................................................. ....... …….............................................................................