SAJC 2022 Prelim P2 QP + Guide

1 SAJC Prelims 2022 9749/02 [Turn Over Class Index Number Name 21S ST. ANDREW’S JUNIOR COLLEGE JC 2 2022 Preliminary Examination _________________________________________________________________________ PHYSICS, Higher 2 9749/02 Paper 2 Structured Questions 12th September 2022 2 hours Candidates answer on the Question Paper. No Additional Materials are required. _________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name, index number and Civics Group in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use an 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. 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 / 9 2 / 9 3 / 11 4 / 10 5 / 7 6 /12 7 / 22 Total / 80 This document consists of 21 printed pages including this page.

2 SAJC Prelims 2022 9749/02 [Turn Over Data speed of light in free space c = 3.00 x 108 m s-1 permeability of free space o = 4  x 10-7 H m-1 permittivity of free space o = 8.85 x 10-12 F m-1 = (1/(36)) x 10-9 F m-1 elementary charge e = 1.60 x 10-19 C the Planck constant h = 6.63 x 10-34 J s unified atomic mass constant u = 1.66 x 10-27 kg rest mass of electron me = 9.11 x 10-31 kg rest mass of proton mp = 1.67 x 10-27 kg molar gas constant R = 8.31 J K-1 mol-1 the Avogadro constant NA = 6.02 x 1023 mol-1 the Boltzmann constant k = 1.38 x 10-23 J K-1 gravitational constant G = 6.67 x 10-11 N m2 kg-2 acceleration of free fall g = 9.81 m s-2 Formulae uniformly accelerated motion s = u t + ½ a t2 v2 = u2 + 2 a s work done on/by a gas W = p V hydrostatic pressure p =  g h gravitational potential  = r Gm− temperature T / K = T / oC + 273.15 pressure of an ideal gas p = 1 3 Nm V 〈c2〉 mean translational kinetic energy of an ideal gas molecule E = 2 3 kT displacement of particle in s.h.m. x = xo sin  t velocity of particle in s.h.m. v = v0 cos  t v =   22 0 xx − electric current I = Anvq resistors in series R = R1 + R2 + ... resistors in parallel 1 / R = 1 / R1 + 1 / R2 + ... electric potential V = r Q 04 alternating current/voltage x = xo sin  t magnetic flux density due to a long straight wire B = μ0I 2πd magnetic flux density due to a flat circular coil B = μ0NI 2r magnetic flux density due to a long solenoid B = μ0nI radioactive decay x = xo exp (- t) decay constant  = 2/1 2ln t

3 SAJC Prelims 2022 9749/02 [Turn Over Answer all the questions in the space provided. 1 (a) Fig. 1.1 shows a block of mass 0.30 kg released from rest at a height of 0.10 m above a light spring of force constant 80 N m -1. The block lands on the light board and compresses a vertical spring before rebounding. The spring obeys Hooke’s law. Assume that all the energy the block loses becomes elastic pote ntial energy in the spring. (i) Calculate the maximum compression of the spring. maximum compression = …………………. m [2] (ii) When the spring is compressed, the block attains a maximum kinetic energy before coming to a momentary stop. At the position where the block has maximum kinetic energy, 1. show that the compression of the spring is 0.037 m, and Fig. 1.1 0.10 m 0.30 kg light board

4 SAJC Prelims 2022 9749/02 [Turn Over [1] 2. determine the maximum kine tic energy attained by the block using energy considerations. maximum kinetic energy = ………………………. J [3] (iii) On Fig. 1.2, show the variation with position of the block of the kinetic energy (label this KE), gravitational potential energy (label this GPE) and elastic potential energy (label this EPE) of the block-spring system. Take the gravitational potential en ergy to be zero when the spring is at maximum compression. There is no need to indicate numerical values. [3] energy Fig. 1.2 maximum compression of spring position total energy spring starts to compress release of block

5 SAJC Prelims 2022 9749/02 [Turn Over 2 (a) A satellite is orbiting the Earth in a circular orbit with a period of 24 hours. (i) State two conditions under which the orbit of this satellite is geostationary. 1. ………………………………………………….………………………………….. …………………………………………………….…………………………………… 2. ………………………………………………….………………………………….. …………………………………………………….…………………………………… [2] (ii) Suggest one advantage of a geostationary satellite used for communiation. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………………… [1] (b) (i) An isolated solid sphere of radius r may be assumed to have its mass M concentrated at its centre. The magnitude of the gravitational potential at the surface of the sphere is . On Fig. 2.1, show the variation of the gravitational potential with distance d from the centre of the sphere for values of d from d = r to d = 4r. Fig 2.1 [2] Fig. 2.1

6 SAJC Prelims 2022 9749/02 [Turn Over (ii) The sphere in (b)(i) is a planet with radius r of 6.4 × 10 6 m and mass M of 6.0 × 10 24 kg. The planet has no atmosphere. A rock of mass 3.4 × 10 3 kg moves directly towards the planet. Its distance from the centre of the planet changes from 4r to 3r. Calculate the change in gravitational potential energy of the rock. change = ....................................................... J [2] (iii) Explain whether the rock’s speed increases, decreases or stays the same as it moves towards the planet. ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..………………………………[2]

7 SAJC Prelims 2022 9749/02 [Turn Over 3 (a) A double-slit interference experiment is set up using coherent red light as illustrated in Fig. 3.1. Fig. 3.1 (not to scale) The separation of the slits is 0.86 mm. The distance of the screen from the double slit is 2.4 m. A series of light and dark fringes is observed on the screen. (i) State what is meant by coherent light. ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..………………………………[1] (ii) Estimate the separation of the dark fringes on the screen. separation = ….……….……mm [3]

8 SAJC Prelims 2022 9749/02 [Turn Over (iii) Initially, the light passing through each slit has the same intensity. The source is adjusted so that the intensity of the light passing through one of the two slits is reduced. State and explain the effect, if any, on the dark fringes observed on the screen. ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..…………………………………… ……………………………………………………………………………………………..………………………………[3] (b) Microwave ovens cook food by generating electromagnetic radiation that gets absorbed and converted into the internal energy of the atoms and molecules of the food. A device called a magnetron emits electromagnetic radiation of frequency 2.45 GHz from one side of the microwave oven as shown in Fig. 3.2. Standing waves are produced in the oven’s interior.