2013 MJC H2 Physics P2

This question paper consists of 20 printed pages MERIDIAN JUNIOR COLLEGE Preliminary Examination Higher 2 _______________________________________________________________________ H2 Physics 9646/2 Paper 2 18 September 2013 1 hour 45 min _______________________________________________________________________ Class Reg Number Candidate Name _____________________________ READ THESE INSTRUCTIONS FIRST This booklet contains 7 questions. Do not open this booklet until you are told to do so. Answer all questions. Write your answers on this question booklet in the blanks provided. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. Marks will be deducted if units are not stat ed where necessary or if answers are not quoted to t he appropriate number of significant figures. All working for numerical answers must be shown. You are reminded of the need for good English and clear presentation of your answers. Examiner’s Use Section A Q1 /10 Q2 /10 Q3 /10 Q4 / 9 Q5 / 6 Q6 /15 Q7 /12 Deductions Total /72

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 2 Data speed of light in free space c = 3.00 x 108 m s-1 permeability of free space o = 4 x 10-7 H m-1 permittivity of free space ε0 = 8.85 x 10-12 F m-1 = (1/(36)) 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 = ut + 1 2 at2 v2 = u2 + 2as work done on/by a gas W = pV hydrostatic pressure p = gh gravitational potential  =  Gm r displacement of particle in s.h.m. x = xo sin t velocity of particle in s.h.m. v = vo cos t =   22 o -x x mean kinetic energy of a molecule of an ideal gas E = 3 2 kT resistors in series R = R1 + R2 + … resistors in parallel 1/R = 1/R1 + 1/R2 + … electric potential V = 04 Q r alternating current/voltage x = xo sin t transmission coefficient T  exp(-2kd) where k =   2 2 8( )mU E h radioactive decay x = xo exp(-t ) decay constant  = 1 2 0.693 t

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 3 Answer all the questions in the spaces provided. 1 (a) A student submerges fully a stone of mass 200 g that is suspended from a cord in a beaker of water as shown in Fig. 1.1. (Density of water = 1000 kg m-³) (i) Given that the volume of stone is 50 cm3, calculate the force sensor reading F. F = ………………..… N [2] (ii) The student decides to now place the stone into a beaker of oil such that it is fully submerged. Explain, with appropriate equation, how the reading on the force sensor will change. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………….. [2] Fig. 1.1 Force Sensor Beaker of water

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 4 (b) (i) State the two conditions that need to be met for an object to be at equilibrium. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………….. [2] (ii) A simple bridge consists of a rigid roadway supported at ends A and B. A car is in the position as shown in Fig. 1.2. Fig. 1.2 The total load on the rear wheels of the car is 1.50 kN and on the front wheels is 3.50 kN.The distance between the front and rear wheels is 1.80 m. The rear wheels are 2.00 m from A, and the front wheels 5.00 m from B. The vertical forces at the supports A and B of the bridge due to the car are NA and NB respectively. Determine the value of NA and NB. NA = ………………. N NB = ………………. N [2] 2.00 m 1.80 m 5.00 m A B NA NB 1.50 kN 3.50 kN

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 5 (c) Explain why acceleration-time graphs for cars can be almost vertical but its velocity-time graphs cannot. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ………………………………………………………………………………………………… [2] 2 (a) Define gravitational field strength. ………………………………………………………………………………………………………. ……………………………………………………………………………………………….. [1] (b) Two stars of equal masses are in circular orbit about a common centre as shown in Fig 2.1. Fig 2.1 The mass of each star is M and their separation is 2R. The speed of each star is v. (i) Determine the speed of each star, v, in terms of G, M and R. [2] 2R v v

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 6 (ii) Hence or otherwise, show that the period of revolution T of each star is given by the expression 2316 RT GM  [ 2 ] (b) The total energy E of the star system is given by the expression 2 4 GME R This particular star system is unstable and loses energy over time. (i) Using conservation of energy, show that 2 4 GME R . [1] (ii) Explain how the loss of energy implies that the orbital period of the stars will decrease. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………… [2]

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 7 (iii) For an unstable star system with R = 6.5 105 km and M = 3.0  1030 kg, the rate of decrease of the period of star system is 7.0  10-5 s per year. Estimate the time, in years, when the stars will crash into each other. time = ……………………. yrs [2]

Preliminary Examination Meridian Junior College 18 September 2013 JC2 H2 Physics 2013 8 3 (a) A rectangular coil is rotating about an axis between two magnets with uniform angular velocity ω. The uniform magnetic field B between the two magnets is 0.80 T. The coil is rotating at 50 revolutions per second. The number of turns N of the coil is 30. The cross- sectional area A of the coil is 2.5 m 2. A current is found going through the resistor R with resistance of 40 Ω. Fig. 3.1 shows the instant when the plane of the coil is in a horizontal position. Fig. 3.1 (i) Explain how the current flowing through the resistor R is formed. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………. [2] (ii) Show that the variation of the current I through resistor R with time is given by the expression  471cos 100 tI Take Fig. 3.1 as the orientation of the coil at t = 0 s. You are required to show all your steps clearly. [2] N S R

Preliminary Examination Meridian Junior Co