2024 TJC H2 Prelim Paper 3 with solutions (QP + ANS)

TEMASEK JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG PHYSICS 9749/03 Paper 3 Longer Structured Questions 9 September 2024 2 hours Candidates answer on the Question Paper. No additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, CG and subject tutor’s name on all the work you hand in. 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. Section A Answer all questions. Section B Answer one question only You are advised to spend one and a half hour 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. For Examiner’s Use Section A 1 2 3 4 5 6 Section B 7 8 s.f. Total This document consists of 24 printed pages.

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 2 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 or (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 Js 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 = ut + ½ at2 v2 = u2 + 2as work done on/by a gas W = p ΔV hydrostatic pressure p = gh gravitational potential  = –Gm/r temperature T/K = T/oC + 273.15 pressure of an ideal gas p = 3 1 V Nm < c2 > mean translational kinetic energy of an ideal gas molecule E = 2 3 kT displacement of particle in s.h.m. x = xosint velocity of particle in s.h.m. v = vocost = )( 22 xxo −  electric current I = Anvq resistors in series R = R1 + R2 + .... resistors in parallel 1/R = 1/R1 + 1/R2 + .... electric potential V = rε4π Q o alternating current/voltage x = xo sint magnetic flux density due to a long straight wire B = 𝜇𝑜𝐼 2𝜋𝑑 magnetic flux density due to a flat circular coil B = 𝜇𝑜𝑁𝐼 2𝑟 magnetic flux density due to a long solenoid B = onI

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 3 [Turn over Section A Answer all the questions in the spaces provided. (ii) The boy now puts a weighing scale under him to read his weight from the scale. Explain whether there is a difference in the readings on the weighing scale if the boy stands on the same weighing scale at the North pole. [2] 1 The Earth may be assumed to be a uniform sphere of radius 6400 km and mass 6.02 x 1024 kg. (a) A 50.0 kg boy is standing still on a flat ground located at latitude 35.6 o north of the Equator, somewhere in Japan, as shown in Fig 1.1. (i) Draw and label all the forces acting on the boy on Fig. 1.2. [2] Fig. 1.1 Equator Earth Fig. 1.2 boy

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 4 height = m [3] (ii) Explain whether it is a geostationary satellite above the boy. [1] (b) A satellite orbiting the Earth with a period of 24 hours and flew directly above the boy from west to east. The satellite is under the influence of gravitational force alone. (i) Determine the height of the satellite above the boy.

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 5 [Turn over 2 (a) The first law of thermodynamics may be given by the expression U Q W =+ State the meaning of positive values for each of the symbols in this equation. [1] (b) The specific latent heat of vaporization of water at atmospheric pressure of 1.0 105 Pa is 2.3 106 J kg-1. A mass of 0.37 kg of liquid water at 100 oC is provided with thermal energy needed to vaporize all of the water at atmospheric pressure. (i) Calculate the thermal energy Q supplied to the water. Q = J [1] (ii) The mass of 1 mole of water is 18 g. Assume that water vapour can be considered to behave as an ideal gas. Show that the volume of water vapour produced is 0.64 m3. [2] (iii) Assume that the initial volume of liquid water is negligible compared with the volume of water vapour produced. Determine the magnitude of the work done by the water in expanding against the atmosphere when it vaporizes. work done = J [2]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 6 (iv) Use your answers in (b)(i) and (b)(iii) to determine the increase in internal energy of the water when it vaporizes at 100 oC. Explain your reasoning. Increase in internal energy = J [2] (v) State and explain at the molecular level what contributes to this increase in internal energy of the water when it vaporizes at 100 oC. [2]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 7 [Turn over 3 Fig. 3.1 shows a mass-spring system placed on a frictionless slope. The slope has an angle of θ from the horizontal. When a block of mass m is hung, the spring stretches by an extension of e and the mass remains in equilibrium. The spring is further extended by x downwards, along the slope, and released for the mass-spring system to oscillate. The spring constant is k. (a) By using Newton’s second law, show that the acceleration a of the block at the lowest point is given by a = − k xm . [2] (b) The amplitude of oscillation of the mass-spring system is 3.0 cm. Calculate the position of the mass from equilibrium when the speed of the mass is 25 % of the maximum speed. position = cm [2] equilibrium position  frictionless slope fixed block Fig. 3.1

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 8 (c) A student removes the fixed block and attaches a variable frequency oscillator to the mass - spring system, as shown in Fig. 3.2. Fig. 3.3 shows the variation of the amplitude of mass with the frequency of the oscillator. Fig. 3.2 (i) Explain the phenomenon illustrated in Fig. 3.3. [2] equilibrium position  frictionless slope variable frequency oscillator mass, m amplitude / cm frequency / Hz 1.0 1.2 1.4 2.0 4.0 6.0 Fig. 3.3

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9 [Turn over (ii) Using Fig. 3.3 calculate the magnitude of maximum acceleration of the mass. acceleration = m s−2 [2]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 10 4 (a) State Coulomb’s law between 2 point charges. [1] (b) A positive point charge + Q is positioned at a fixed point X and an identical positive point charge is positioned at a fixed point Y, as shown in Fig. 4.1. The charges are separated in a vacuum by a distance of 10.0 cm. Point A and B are on the line XY. Point A is a distance of 2.5 cm from X an