ACJC 2022 Prelim P2

This paper consists of 25 printed pages Anglo-Chinese Junior College Physics Preliminary Examination Higher 2 CANDIDATE NAME CLASS CENTRE NUMBER S 3 0 0 4 INDEX NUMBER PHYSICS Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9749/02 25 August 2022 2 hours READ THESE INSTRUCTIONS FIRST Write your name, class and index number 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, graphs or rough working. Do not use staples, paper clips, 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 Examiners’ use only 1 / 6 2 / 12 3 / 8 4 / 9 5 / 11 6 / 14 7 / 20 Total / 80

2 Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination DATA AND FORMULAE Data speed of light in free space, c = 3.00  108 m s−1 permeability of free space, o = 4  10−7 H m−1 permittivity of free space, o = 8.85  10−12 F m–1 (1/(36))  10–9 F m–1 elementary charge, e = 1.60  10−19 C the Planck constant, h = 6.63  10−34 J s unified atomic mass constant, u = 1.66  10−27 kg rest mass of electron, me = 9.11  10−31 kg rest mass of proton, mp = 1.67  10−27 kg molar gas constant, R = 8.31 J K−1 mol−1 the Avogadro constant, NA = 6.02  1023 mol−1 the Boltzmann constant, k = 1.38  10−23 J K−1 gravitational constant, G = 6.67  10−11 N m2 kg−2 acceleration of free fall, g = 9.81 m s−2

3 [Turn over Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination Formulae uniformly accelerated motion, s = ut + 2 1 at 2 v 2 = u 2 + 2as work done on/by a gas, W = p V hydrostatic pressure, p =  g h gravitational potential,  = − Gm r temperature T/K = T/oC + 273.15 pressure of an ideal gas p = 21 3 Nm c V  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 = vo cos t =   22 oxx − electric current I = Anvq resistors in series, R = R1 + R2 +  resistors in parallel, 1/R = 1/R1 + 1/R2 +  electric potential, V = 4 o Q r alternating current/voltage, x = xo sin t magnetic flux density due to a long straight wire B = 2 o d   magnetic flux density due to a flat circular coil B = 2 oN r  magnetic flux density due to a long solenoid B = on radioactive decay, x = xo exp(−t) decay constant,  = 12 ln2 t

4 Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use Answer all the questions in the spaces provided. 1 (a) In an experiment to determine the thickness of a typical $1 coin, a student used a half meter rule to determine the thickness of one $1 coin and the thickness T of N such coins, as shown in Fig. 1.1. Fig. 1.1 The thickness of a typical $1 coin is then taken to be T N . (i) In finding the thickness of a $1 coin, e xplain how dividing T by N reduces random error as compared to measuring the thickness of only 1 coin. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………... [2] (ii) Suggest a method to further improve the accuracy in determining the thickness of the coin. Explain your answer. ………………………………………………….…………………………………… ……………………………………………………….……………………………… …………………………………………………………………………………... [1]

5 [Turn over Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use (b) The ideal gas law states that pV = nRT where p is the pressure of the gas, V is the volume of the gas, n is the number of moles and T is the thermodynamic temperature. In an experiment, the student was attempting to calculate the value of p for a sample of 2.00 millimoles of gas trapped in a sphere. Assuming ideal gas conditions, if the diameter of the sphere is (50.0 ± 0.1) mm and the temperature of the gas is (36.7 ± 0.1) °C, determine the value of p with its associated uncertainty. p = (………………….. ± …………………..) Pa [3] [Total: 6]

6 Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use 2 (a) A man wants to knock down a coconut from the tree by throwing a stone at it as shown in Fig. 2.1. The coconut is 18.0 m above the ground. The man’s hand is 2.2 m above the ground when he release s the stone with an initial velocity of 20.0 m s–1. Assume that air resistance is negligible. Fig. 2.1 (not to scale) (i) Explain qualitatively, in terms of acceleration and velocity, why the path taken by the stone is parabolic. ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………... [1] (ii) Show that the angle at which the stone should be released from the horizontal so that it would hit the coconut horizontally is 62°. [2] 18.0 m 2.2 m

7 [Turn over Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use (iii) Hence, calculate the time taken for the stone to reach its maximum height when it is projected at the angle in (a)(ii). time taken = ……………………… s [2] (b) A spaceship engine uses solar power to ioni se and eject xenon atoms from the spaceship. The speed of the ejected xenon ions is 3.0  104 m s–1 relative to the spaceship as shown in Fig. 2.2. Fig. 2.2 Fig. 2.3 shows the variation with time t of the acceleration a of the spaceship due to the ejection of xenon ions. Fig. 2.3 t /107 s 10.0 9.5 9.0 8.5 8.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 xenon ions 3.0  104 m s–1 spaceship a /10–5 m s–2

8 Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use (i) Explain why the acceleration of the spaceship is increasing. ……………………………………………………….……………………………… .……………………………………………………………………………………… …………………………………………………………………………………... [1] (ii) Given that the ions are ejected at a constant rate of 1.7  10–6 kg s –1, calculate the magnitude of the force exerted on the spaceship by the ions. magnitude of force = ……………………… N [2] (iii) The spaceship is initially stationary and its engine is switched on at time t = 0 s. Using Fig. 2.3, calculate the final velocity of the spaceship when the xenon ions run out completely. velocity = ……………………… m s–1 [2]

9 [Turn over Anglo-Chinese Junior College 2022 J2 H2 9749 Paper 2 Preliminary Examination For Examiner’s Use (iv) On Fig. 2.4, draw the corresponding variation with time t of the velocity v of the spaceship from t = 0 to t = 6.0  107 s. Fig. 2.4 [2] [Total: 12]

10 Anglo-Chinese Junior College