Prelim (H2) P2 2021 QP and Solutions

1 Class Index Number Name 20S ST. ANDREW’S JUNIOR COLLEGE JC 2 2021 Preliminary Examination PHYSICS, Higher 2 9749/02 Paper 2 Structured Questions 13th September 2021 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. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. 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. For Examiner’s Use 1 / 7 2 / 10 3 / 8 4 / 6 5 / 13 6 / 8 7 / 6 8 / 22 Total / 80 This document consists of 25 printed pages including this page. SAJC 2021 Preliminary Examination / 9749 [Turn Over

2 Data speed of light in free space, c = 3.00 x 108 m s-1 permeability of free space, mo = 4 p x 10-7 H m-1 permittivity of free space, eo = 8.85 x 10-12 F m-1 = (1/(36p)) 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 DV hydrostatic pressure, p = g h gravitational potential, f = −Gm r 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 = 3 2 kT displacement of particle in s.h.m., x = xo sin t velocity of particle in s.h.m., v = v0 cos w t v = ± w √ x0 2−x2 electric current I = Anvq resistors in series, R = R1 + R2 + ... resistors in parallel, 1 / R = 1 / R1 + 1 / R2 + ... electric potential, V = Q 4 πε0 r alternating current/voltage, x = xo sin  t magnetic flux density due to a long straight wire, B = μ0 I 2πd magnetic flux density due to a flat circular coil, B = μ0 NI 2r magnetic flux density due to a long solenoid, B = μ0 n I radioactive decay, x = xo exp (-l t) SAJC 2021 Preliminary Examination / 9749 [Turn Over

3 decay constant,  = ln 2 t1/2 Answer all questions in the spaces provided. 1 Experimental measurements of the gravitational constant G in different years are shown in the table. (a) State the year in which the measurement of G appears to be the most precise. Explain your answer. ……………………………………………………………………………………………………. ………………………………………………………………………………………………… [1] (b) The value of G was determined in 2010 at the University of Zurich. The value was consistent with the value obtained in the 2007 experiment but was not consistent with the values from 2000 or 2009. The experimenter who obtained the value for G in 2010 thinks that there is probably a systematic error in each of the other two experiments. (i) Explain what is meant by a systematic error. ……………………………………………………….…………………………………….. ……………………………………………………….………………………………… [1] (ii) Explain why the most precise result may not be the most accurate. ……………………………………………………….…………………………………….. ……………………………………………………….…………………………………….. ……………………………………………………….………………………………… [2] SAJC 2021 Preliminary Examination / 9749 [Turn Over

4 (c) In year 2009, experimental measurements were made of the mass of Earth, mass of Moon, and the gravitational force between Earth and Moon. mass of Earth, M 5.972 × 1024 ± 1% kg mass of Moon, m 7.348 × 1022 ± 2% kg gravitational force between Earth and Moon, F (1.98 ± 0.02) × 1020 N The distance between the centres of Earth and moon, R, is estimated to be around 3.844 × 108 m. Express R and its actual uncertainty ∆R. Show your working clearly. R ± ∆R = …………………… ± …………………… m [3] SAJC 2021 Preliminary Examination / 9749 [Turn Over

5 2 (a) A ball is released from rest a distance h above a rigid horizontal surface and it rebounds along its original path inelastically. Taking air resistance as negligible and downwards as positive, sketch on the axes provided, for at least 2 bounces, its corresponding graph representing the variation with time t of (i) its displacement, s [2] (ii) its velocity, v [2] SAJC 2021 Preliminary Examination / 9749 [Turn Over h 0 t s 0 t v

6 (b) When the ball is released at height h above the ground, it reaches the ground with speed 3.8 m s -1. The ball is then in contact with the floor for a time of 0.081 s before leaving it with speed 1.7 m s-1. The mass of the ball is 0.062 kg. Fig. 2.1 (i) Calculate height h. h = ………………………… m [1] (ii) Calculate the magnitude of the average force the ground acts on the ball during the collision. magnitude of the average force = ………………………… N [2] SAJC 2021 Preliminary Examination / 9749 [Turn Over

0 V -V 10.0 cm 20.0 cm 45 45 metal plate metal plate 3.0 m s-1 7 (c) Two parallel metal plates, each of length 20.0 cm, are separated by 10.0 cm, as illustrated in Fig. 2.2 below that is not drawn to scale. Fig. 2.2 The plates are in a vacuum. A small ball bearing of charge +4.4 × 10 -7 C and mass 1.0 × 10 -4 kg with an initial speed 3.0 m s -1 enters the plates at an angle of 45° below the horizontal, and just leave the plates at an angle of 45° above the horizontal, as shown in Fig. 2.2. Calculate the potential V of the plate at the top. V = …………………………. V [3] SAJC 2021 Preliminary Examination / 9749 [Turn Over

8 3 (a) A photon of wavelength 940.0 × 10-12 m collides with an isolated stationary electron, as illustrated in Fig. 3.1. Fig. 3.1 The photon is deflected elastically by the electron. The wavelength of the deflected photon is 941.1 × 10-12 m. (i) Without making any calculations, sketch in the space below a vector triangle to show conservation of momentum. Label the triangle with the initial momentum p1 of incident photon, the final momentum p2 of electron, and the final momentum p3 of the deflected photon. [2] (ii) Calculate the final momentum p3 of the deflected photon. p3 = ……………………. N s [1] SAJC 2021 Preliminary Examination / 9749 [Turn Over 941.1 × 10-12 m deflected electron momentum p2θ 56.9 °940.0 × 10-12 m

9 (iii) Calculate the kinetic energy of the deflected electron. kinetic energy = ……………………. J [2] (iv) Using your answer in (a)(i), or otherwise, determine p2 and θ. p2 = ……………………………… N s θ = ……………………………… ° [3] SAJC 2021 Preliminary Examination / 9749 [Turn Over

10 4 (a) Define the moment of a force about a point. ……………………………………………………………………………………………………. ………………………………………………………………………………………………… [1] (b) A fishing rod AB is shown in Fig. 4.1. Fig. 4.1 End A of the rod fixed to the ground and a string is attached to the other end B. A support stick exerts a force perpendicular to the rod at point C. The weight of the rod acts at point D. The tension T in the string is in a direction perpendicular to the rod. The rod is in equilibrium and inclined at an angle of 56° to the vertical. The forces and the distances along the rod of points A, B, C and D are shown in Fig. 4.1. (i) Calculate the tension T. T = ………………………………. N [2] SAJC 2021 Preliminary Examination / 9749