2021 J2 H2 Physics Prelim P3

This paper consists of 26 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 3 Longer Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9749/03 1 September 2021 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. 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. For Examiners’ use only Section A 1 / 9 2 / 13 3 / 9 4 / 13 5 / 16 Total / 60 Section B 6 / 20 7 / 20 Grand Total / 80

2 Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use 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 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use 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,  =  r Gm temperature T / K = T / oC + 273.15 pressure of an ideal gas p = 21 3 Nm cV  mean translational kinetic energy of 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 xxo  electric current I = A n v q resistors in series, R = R1 + R2 +  resistors in parallel, 1/R = 1/R1 + 1/R2 +  electric potential, V = r Q o4 alternating current/voltage, x = xo sin t magnetic flux density due to a long straight wire B = 2 o d   I magnetic flux density due to a flat circular coil B = 2 oN r  I magnetic flux density due to a long solenoid B = on I radioactive decay, x = xo exp(t) decay constant,  = 12 t ln2

4 Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use Section A Answer all questions in the spaces provided. 1 (a) A solid cylinder of height h and density ρ rests on a flat surface as shown in Fig. 1.1. Fig. 1.1 Show that pC = hρg where pC is the pressure exerted by the cylinder on the surface. [2] (b) Fig 1.2 shows a tube of constant circular cross -section, sealed at one end, contains an ideal gas trapped by a cylinder of mercury of length 0.035 m. The whole arrangement is in the Earth’s atmosphere. The density of mercury is 1.36 × 104 kg m-3. Fig. 1.2 When the mercury is above the gas column the length of the gas column is 0.190 m.

5 [Turn over Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use (i) Explain what is meant by an ideal gas. ………………………………………….…………………………………………… ………………………………………….…………………………………………… ……………………………………………………………………………….……… ………………………………………………………………………………….…… …………………………………………………………………………………… [2] (ii) Given po = atmospheric pressure pm = pressure due to the mercury column T = temperature of the trapped gas n = number of moles of the trapped gas A = cross-sectional area of the tube Show that ( ) 0.190om nRTpp A   . [1]

6 Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use (iii) The tube is slowly rotated until the gas column is above the mercury. The length of the gas column is now 0.208 m. The temperature of the trapped gas does not change during the process. Determine po. po = ……………………………. Pa [2] (iv) Using the First Law of Thermodynamics, explain the heat exchange between the gas and the surrounding during the process mentioned in (b)(iii). ………………………………………….…………………………………………… ………………………………………….…………………………………………… ………………………………………………………………………….…………… …………………………………………………………………………….………… …………………………………………………………………………………… [2]

7 [Turn over Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use 2 (a) State the principle of conservation of momentum. ……………………………………………………………………………..................... ……………………………………………………………………………..................... ……………………………………………………………………………………….. [2] (b) Two frictionless trolleys A and B are moving along a horizontal straight line, as illustrated in Fig. 2.1. Fig. 2.1 Trolley A has mass 1.2 kg and a velocity of 6.40 m s-1. Trolley B has mass 5.2 kg and a velocity of 0.30 m s-1. At 0.20 s, the two trolleys collide elastically and are in contact for a duration of 0.47 s and trolley A moves in the opposite direction after the collision. (i) Show that the velocity of trolley B after the collision is 2.6 m s-1. [3] A B 6.40 m s-1 0.30 m s-1 5.2 kg 1.2 kg

8 Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use (ii) Calculate the average force F that B exerts on A during the collision. F = ……………………………. N [3] (iii) Sketch on Fig. 2.2, the velocity-time graph for trolley A. The velocity-time graph of trolley B has been provided. [2] (iv) Indicate on Fig. 2.2 the time at which the two trolleys are the closest to each other. Label this time as tc. [1] (v) Discuss why the collision is elastic even though the magnitude of the kinetic energy of the system at tc is not the same as that before the collision. ……………………………………………………………………………............ ……………………………………………………………………………............ ……………………………………………………………………………............ ……………………………………………………………………………....... [2] velocity / m s-1 time / s 0.20 0.67 0 0.30 2.59 Fig. 2.2

9 [Turn over Anglo-Chinese Junior College 2021 J2 H2 9749 Paper 3 Preliminary Examination For Examiner’s Use 3 (a) (i) Define electric field strength at a point. ………………..……………………...…………………...……………….………… ……..…………………….…………………………………………………..….. [1] (ii) State the relationship between electric