EJC 2020 J1H2 Promo P2

©EJC 2020 9749/02/J1H2PROMO/2020 [Turn over EUNOIA JUNIOR COLLEGE JC1 Promotional Examination 2020 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 0 - REGISTRATION NUMBER PHYSICS Paper 2 Structured Questions 9749/02 02 October 2020 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number 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 paper clips, highlighters, glue or correction fluid. The use of an approved scientific calculator is expected where appropriate. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 24 printed pages For Examiner’s Use 1 2 3 4 5 6 7 8 9 S.F. Total

2 ©EJC 2020 9749/02/J1H2PROMO/2020 Data speed of light in free space, c = 3.00  108 m s–1 permeability of free space, μo = 4π  10–7 H m–1 permittivity of free space, εo = 8.85  10–12 F m–1 (1/(36 π))  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 ©EJC 2020 9749/02/J1H2PROMO/2020 [Turn over Formulae uniformly accelerated motion, s = ut + ½at2 v2 = u2 + 2as work done on/by a gas, W = pΔV hydrostatic pressure, p = ρgh gravitational potential,  = Gm r temperature, T/K = T / oC + 273.15 pressure of an ideal gas, p = 21 3 Nm cV mean translational kinetic energy of an ideal gas molecule E = 3 2 kT displacement of particle in s.h.m. x = xo sin ωt velocity of particle in s.h.m. v = vo cos ωt =  22 xxo  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 ωt 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 (–λt) decay constant λ = 1 2 ln2 t

4 ©EJC 2020 9749/02/J1H2PROMO/2020 1 A water bomb is launched at ground level at a velocity of 20 m s -1 at an angle of 5 0° from the horizontal to hit a boy on top of a platform of height H at a position 32 m from the foot of the building. The boy is standing at a distance x from the edge of the platform. Fig. 1.1 (not drawn to scale) The water bomb reaches the top of its trajectory and then fall towards the boy, hitting him 2.75 s after launch. (a) Show that the height of the platform H is 5.0 m. [1] (b) Determine the distance x of the boy from the edge of the building. x  ……………………. m [1] (c) Upon seeing the water bomb being launched at him, the boy runs away from the edge of the platform as soon as possible. Assuming that the water bomb (which explodes upon impact) has a ‘splash radius’ of 5 .0 m and the boy’s reaction time is 0.20 s, calculate the minimum constant acce leration at which the boy should run in order to avoid being splashed. minimum acceleration  ……………………. m s-2 [2] 20 m s-1 50o 32 m H x platform position of boy

5 ©EJC 2020 9749/02/J1H2PROMO/2020 [Turn over (d) State and explain the changes to your answers in (b) if a water bomb of a larger mass is being launched instead at the same velocity. ………………………………………………………...…………………………………………..… ………………………………………………………………...…………………………………..… ……………………………………………………………………...……………………………..… ……..…………………………………………………………………………………………….. [3] [Total: 7]

6 ©EJC 2020 9749/02/J1H2PROMO/2020 2 Fig. 2.1 is a diagram of a human arm lifting an object. Fig. 2.1 The lower arm is horizontal and its centre of gravity is 0.150 m f rom the elbow joint. The weight of the lower arm is 18 N. The bicep muscle exerts a force F at an angle of  to the vertical. The horizontal distance between the elbow joint and the point of attachment of the muscle to the lower arm bone is 0.040 m. The weight of the object held in the hand is 30 N and its centre of gravity is 0.460 m from the elbow joint. The arm is in equilibrium. (a) Determine the value of F when  = 15o. F = ………………………… N [2]

7 ©EJC 2020 9749/02/J1H2PROMO/2020 [Turn over (b) For the lower arm to be in equilibrium, the elbow joint also needs to exert a force R on the lower arm bone. (i) Draw a labelled arrow on Fig. 2.1 to represent the force R that the elbow exerts on the lower arm. [1] (ii) Explain the direction of this force R. …………..…………….……………………………………………………………….…..…. …………..…………….……………………………………………………………………… …………..…………….………………………………………………………………….….. …….…..…………….……………………………………………………………………. [2] (c) As the lower arm is slowly moved away from the body in the horizontal direction, the angle  increases. Sketch in Fig. 2.2 the graph of how F varies with . (You may assume that the lower arm remains horizontal and is in equilibrium at all times.) [1] Fig. 2.2 (d) Suggest and explain what will happen to F if he has a longer lower arm that has the same weight. ………………………………………………………...…………………………………………..… ………………………………………………………………...…………………………………..… ……………………………………………………………………...……………………………..… …………..……………………………………………………………………………………….. [2] [Total: 8] 0 F  90o

8 ©EJC 2020 9749/02/J1H2PROMO/2020 3 (a) State the principle of conservation of momentum. ………………………………………………………………...…………………………………..… ……………………………………………………………………...……………………………..… …………………..……………………………………………………………………………….. [2] (b) A particle A travelling with a velocity of 9.0 × 105 m s-1, along a horizontal frictionless surface collides elastically with another particle B of identical mass, which was initially stationary, as shown in Fig. 3.1. They then move apart as shown in Fig. 3.2. Particle A has velocity 4.5 × 105 m s–1 at an angle of 60o to the direction of its initial path. Particle B has velocity v m s –1 at an angle of θ to the direction of the initial path of particle A. (i) Calculate 1. the magnitude of velocity v v = …………….……. m s-1 [2] 2. the angle θ θ = ……………….o [2] θ 600 v m s-1 4.5 × 105 m s-1 A B A B 9.0 × 105 m s-1 Fig.3.1 Fig.3.2

9 ©EJC 2020 9749/02/J1H2PROMO/2020 [Turn over (ii) Using the principle of conservation of momentum, explain why the momentum of particle A cannot be conserved. …………..…………….……………………………………………………………………… …………..…………….……………………………………………………………………… …………..…………….………………………………………………………………….….. …….…..…………….……………………………………………………………………. [2] [Total: 8]

10 ©EJC 2020 9749/02/J1H2PROMO/2020 4 (a) A box of mass 4.0 kg, is pushed by a varying force F along a rough floor, with a constant frictional force of 2.5 N. The force F varies with the displacement x measured with respect to a fixed point, P on the ground as shown in Fig 4.1. (i) Determine the work done by the force F after it has travelled a displacement of 3.0 m from P. work done by F = …………………. J [1] (ii) Assuming that the box started from re