2018 RI H2 Physics Prelims P2 QP

This document consists of 20 printed pages and 1 blank page. © Raffles Institution 9749/02 [Turn over Centre Number Index Number Name Class S3016 RAFFLES INSTITUTION 2018 Preliminary Examination PHYSICS Higher 2 Paper 2 Structured Questions 9749/02 13 September 2018 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your index number, name and class in the spaces at the top of this page. Write in dark blue or black pen in the spaces provided in this booklet. You may use 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. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 15 2 / 10 3 / 12 4 / 11 5 / 12 6 / 20 Deduction Total / 80

2 © Raffles Institution 9749/02 Data speed of light in free space c = 3.00 × 108 m s−1 permeability of free space 0µ = 4π × 10−7 H m−1 permittivity of free space 0ε = 8.85 × 10−12 F m−1 = (1/(36π)) × 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 Formulae uniformly accelerated motion s = 21 2ut at+ 2v = 2 2u as+ work done on/by a gas W = pV∆ hydrostatic pressure p = ρgh gravitational potential φ = Gm r− temperature T/K = / C 273.15T °+ 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 = 0 sinxt ω velocity of particle in s.h.m. v = 0 cosvt ω 22 0xxω= ±− electric current I = Anvq resistors in series R = 12 ...RR++ resistors in parallel 1/R = 121 1 ...RR++ electric potential V = 4 Q rε0π alternating current/voltage x = 0 sinxt ω magnetic flux density due to a long straight wire B = 0 2 d µ π I magnetic flux density due to a flat circular coil B = 0 2 N r µ I magnetic flux density due to a long solenoid B = 0nµ I radioactive decay x = ( )0 expxt λ− decay constant λ = 1 2 ln2 t

3 © Raffles Institution 9749/02 [Turn over Answer all the questions in the spaces provided. 1 (a) (i) State Newton’s Second Law of Motion as applied to a system of bodies. [2] (ii) Explain the implication of Newton’s Second Law for a system of bodies isolated from all external forces. [2] (b) Two blocks A and B are held together with a light spring in between them as shown in Fig. 1.1. The spring has a force constant 80 N m−1 and is compressed by 0.060 m. Fig. 1.1 The masses of blocks A and B are 0.100 kg and 0.050 kg respectively. Upon release, the two blocks move off in opposite directions on a smooth table surface and the spring falls off. (i) On Fig. 1.2, sketch a graph to show the variation with time t of the force exerted by the spring on block B during which B is being pushed away from block A. Fig. 1.2 [2] force t 0 A (0.100 kg) B (0.050 kg) table surface

4 © Raffles Institution 9749/02 (ii) Determine the final speeds of the two blocks. speed of block A = m s−1 speed of block B = m s−1 [4] (c) As block B slides forward, it topples over at the edge of the table and lands on a horizontal uniform plank hinged to a wall at O. The centre of block B is at a horizontal distance of 0.15 m from the free end of the plank. The plank is supported by a rope attached to the wall as shown in Fig. 1.3. Fig. 1.3 B rope 0.15 m 0.10 m 55 ° O 0.15 m table surface wall centre line

5 © Raffles Institution 9749/02 [Turn over Given that the weight of the plank is 4.0 N, calculate (i) the tension in the rope after B is at rest on the plank, tension = N [2] (ii) the magnitude of the horizontal and vertical components of the force exerted by the hinge on the plank, magnitude of horizontal component = N magnitude of vertical component = N [2] (iii) the angle θ that the force by the hinge on the plank makes with the horizontal. On Fig. 1.3, draw and label the force F by the hinge and indicate the angle θ . θ = ° [1]

6 © Raffles Institution 9749/02 2 (a) A speaker emits sound waves uniformly in all directions. Fig. 2.1 shows the variation with time t of the displacement x of an air molecule at a point Q that is 120 cm from the speaker. Fig. 2.1 (i) Use Fig. 2.1 to determine the 1. frequency f of the sound waves, f = Hz [1] 2. uncertainty in f calculated in (a)(i)1. caused by reading the scale of the graph. uncertainty in f = Hz [3] t / ms x / mm 0 −0.20 0.20 4.0 3.0 2.0 1.0

7 © Raffles Institution 9749/02 [Turn over (ii) Determine the next earliest time after 1.5 ms when the motion of the air molecule at Q has a phase difference of 4 5 π compared to its phase at 1.5 ms. time = ms [2] (iii) If the power of the source is reduced to 0.25 of its initial value, calculate the distance from the speaker that will have the same intensity as that at point Q. distance = cm [2] (b) The wave arriving at point Q is progressive in nature. A stationary wave may be formed when two identical waves travelling in opposite directions superpose. State the differences between the particles of a progressive wave and particles of a stationary wave in the following aspects: (i) amplitude, [1] (ii) phase difference. [1]

8 © Raffles Institution 9749/02 3 (a) Fig. 3.1 shows two chambers, X and Y, connected by a small pipe which is fitted with a valve. Both chambers are filled with ideal gas and the valve was initially closed. The volume of chambers X and Y are 2.5 m3 and 4.0 m3 respectively. Chambers X and Y are held at temperatures of 450 K and 300 K respectively. The valve is then opened and a state of equilibrium is reached with the temperatures in each chamber remaining unchanged. Fig. 3.1 (i) Determine the number of moles of ideal gas in chamber X, given that the number of moles of ideal gas in chamber Y is 1.2 after equilibrium has been reached. number of moles of ideal gas in X = [2] (ii) Calculate the pressure in both chambers after equilibrium has been reached. pressure = Pa [1] valve chamber X chamber Y ideal gas

9 © Raffles Institution 9749/02 [Turn over (iii) The valve is now closed and a pump is used to remove some ideal gas from chamber Y. State and explain, using the kinetic theory of gas, why the pressure in chamber Y decreases, assuming no change in its temperature.