SAJC Prelim H2 P3 2025 Qn and Ans

1 SAJC 2025 Preliminary Examination / 9749 [Turn Over Class Index Number Name 24S ST. ANDREW’S JUNIOR COLLEGE JC 2 2025 Preliminary Examination PHYSICS, Higher 2 9749/03 Paper 3 Longer Structured Questions 17th September 2025 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 on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a 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. You are advised to spend one and a half hours on Section A and half an hour on Section B. 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 24 printed pages including this page. For Examiner’s Use Section A 1 / 10 2 / 7 3 / 15 4 / 15 5 / 13 Section B 6 / 20 7 / 20 Total / 80

2 SAJC 2025 Preliminary Examination / 9749 [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 2025 Preliminary Examination / 9749 [Turn Over Section A Answer all questions in the spaces provided 1 (a) State what is meant by parabolic motion. ………………….…….…….…….…….…….…….…….…….…….…….…….…….…….….. ……..…….…….…….…….…….…….…….…….…….…….…….…….…….…….…….. [2] (b) A spring is used to launch a metal ball of mass 4.5 × 10 -2 kg up a ramp. The spring is compressed by 8.0 × 10-2 m and held in equilibrium, as shown in Fig. 1.1. Fig. 1.1 The elastic potential energy stored in the spring at this compression is 0.24 J. The ramp is at an angle of 15° to the horizontal. The spring is released and expands quickly back to its original length. (i) Calculate the average force the spring exerts on the ball during the expansion back to its original length. average force = …………………… N [1]

4 SAJC 2025 Preliminary Examination / 9749 [Turn Over (ii) The ball leaves the spring when the spring reaches its original length. Assume that all the elastic potential energy of the spring is transferred to the ball. Calculate the speed of the ball as it leaves the spring. speed = …………………… m s-1 [2] (iii) The ball travels up the slope as shown in Fig.1.2. Fig. 1.2 At point A, the ball has a speed of 2.4 m s -1. The ball will travel 0.20 m along the slope to reach point B, which is the end of the slope. Show that the speed of the ball at point B is 2.2 m s-1. [1] A B 15°

5 SAJC 2025 Preliminary Examination / 9749 [Turn Over (c) The ball will leave the slope at point B. The height of the slope at B from the ground is 0.40 m, as shown in Fig. 1.3. Fig. 1.3 (i) Determine the speed of the ball when it is at the maximum height. speed = …………………… m s-1 [1] (ii) Determine the time just before the ball hits the ground. time = …………………… s [2] (iii) Determine the horizontal displacement travelled by the ball from B to the point just before hitting the ground. horizontal displacement = …………………… m [1] B 15° 0.40 m ground

6 SAJC 2025 Preliminary Examination / 9749 [Turn Over 2 A binary star system consists of two stars X and Y that orbit around their common centre of gravity C. The orbits are circular. Both stars can be considered as point masses. The mass of star X is M and the mass of star Y is 2 M. The common centre of gravity is at a distance of D from star Y, and at a distance of 2D from star X, as shown in Fig. 2.1. Fig. 2.1 (a) Star X orbits with angular velocity ω. Show that the angular velocity of the orbit of star Y is also ω. [1]

7 SAJC 2025 Preliminary Examination / 9749 [Turn Over (b) Deduce an expression, in terms of G, M and D, for the total energy E of the binary star system. [4] (c) The total energy E of the binary star system is negative. Explain the physical significance of this negative value. ………...………………..……………………………………..………………….……………… …………...………………..……………………………………..…….……………………... [1] (d) Explain whether two identical electric charges could form a system in which the charges orbit around a common centre. ……………...………………..………………………………..……………….………………… ……………...………………..………………………………..……………….……………... [1]

8 SAJC 2025 Preliminary Examination / 9749 [Turn Over 3 (a) Two coherent sources X and Y of microwaves of frequency 2.5 × 10 10 Hz are of a distance of 0.18 m apart in a vacuum, as shown in Fig. 3.1. Fig. 3.1 There is a phase difference of 90° between the waves emitted at the two sources. A microwave detector moves along the line PQ, which is parallel to the line joining the two sources and 2.3 m away from it. Point O is on the line PQ at a position that is equidistant from the two sources. Point A is the position on the line PQ where the intensity of the microwaves is the greatest. (i) Explain why the position of greatest intensity is not at point O. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….….. …….…….…….…….…….…….…….…….…….…….…….…….…….…….…….. [2] (ii) On Fig. 3.1, draw a cross (X) to show the position of the point on line PQ where the intensity minimum that is closest to point O occurs. Label this point B. [1] (iii) Use the formula for the double -slit interference of light to calculate the distance between adjacent intensity maxima on the line PQ. distance = …………………… m [2]

9 SAJC 2025 Preliminary Examination / 9749 [Turn Over (b) A pipe is open at one end and closed at the other end with a piston. The piston can slide freely and is at a distance of 45 cm from the open end of the pipe, as shown in Fig. 3.2. Fig. 3.2 A loudspeaker is positioned near the open end of the