SRJC H2 PHY P3

SRJC 2011 9646/Prelim/2011 [Turn Over SERANGOON JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION General Certificate of Education Advanced Level Higher 2 PHYSICS 9646/03 Paper 3 Longer Structured Questions 22 August 2011 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, Civics Group and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer any two questions. You are advised to spend about one hour on each section. At the end of the examination, fasten all your work securely together. The number of marks is given in bracket [ ] at the end of each question or part question. This document consist of 24 printed pages and no blank page. For Examiner’s Use 1 2 3 4 5 6 7 8 Total CIVICS GROUP CANDIDATE NAME INDEX NUMBER SERANGOON JUNIOR COLLEGE Science Department Physics Unit

DATA AND FORMULAE Data speed of light in free space, c = 3.00  108 m s1 permeability of free space, 0 = 4   107 H m1 permittivity of free space, 0 = 8.85  1012 F m1 (1 / (36 )) x 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 = ut + ½ at 2 v2 = u 2 + 2as work done on/by a gas, W = p V hydrostatic pressure, p = gh gravitational potential,  = – r Gm displacement of particle in s.h.m., x = x 0 sin t velocity of particle in s.h.m., v = v o cost v =  22 0 xxω  resistors in series, R = R 1 + R2 + … resistors in parallel, 1/ R = 1/R1 + 1/R2 + … electric potential, V = Q / 4or alternating current/voltage, x = x 0sin t transmission coefficient, T  exp(2kd) where k = 2 2 h E)m(U8 π radioactive decay, x = x0 exp(t) decay constant,  = 2 1 693.0 t

3 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use Section A Answer all the questions in this section 1 (a) Define gravitational potential at a point. ........................................................................................................................... .................. ......................................................................................................... .................. .....................................................................................................[1] (b) Two masses m1 and m2 are placed at positions as shown in the diagram, where m1 = 25 000 kg and m2 = 15 000 kg. (i) Determine the gravitational po tential at the origin due to m1 and m2 respectively. cm0.50.40.3r 22 1  cm12.200.90.18r 22 2  [M1] 15 11 1 1 Jkg10335.3050.0 )25000)(1067.6( r GM    [A1] 11 612 2 (6.67 10 )(15000) 4.973 100.2012 GM Jkgr       [A1] gravitational potential due to m1 = ............................................... J kg-1 [0] gravitational potential due to m2 = ............................................... J kg-1 [3] x/ cm y/ cm 0 4.0 18.0 9.0 3.0 m1 m2

4 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use (ii) Hence, or otherwise, det ermine the total gravitati onal potential energy of a 1000 kg mass placed at the origin. 1565 T Jkg1083.3)10973.4(10335.3   [M1] J1083.3)1083.3)(1000(mU 25   [A1] total gravitational potential energy = ........ ........................................... J [2] (iii) State the work required to move the 1000 kg mass from the origin to infinity. J1083.3W 2 work done = ...... ......................................... J [1]

5 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use 2 The figure below shows the variation of pr essure with volume for a fixed mass of ideal gas. The gas is taken from state A to st ate C through two different paths ABC and path ADC. (a) Calculate the number of moles in the gas. 75 Consider point C, 1.89 10 7.0 10 8.31 1200 0.133 [A1 ] pV nRT pVn RT      number of moles of gas = …………………… [1] D 1.89  107 P/ Pa V/ 105 m3 1.50  106 7.0 50.0 C 1200 K A B 95.2 K

6 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use (b) (i) During process BC, the temperature of the gas rises from 95.2 K to 1200 K at constant volume. The molar heat capacity of the gas at constant volume is 12.5 J K 1 mol1. During process AB, 1613 J of thermal energy is lost. By showing your working clearly, calc ulate the change in internal energy from A to C. [Note: Molar heat capacity is the am ount of thermal en ergy required to raise the temperature of one mole of gas by one degree Celcius] change in internal energy = …………………….. J [3] (ii) Hence, calculate the thermal energy lost during process ADC. thermal energy lost = …………………….. J [2] (c) To bring the gas from state A to st ate C, less heat is needed for process ADC compared to process ABC. Explain why. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………. [2]

7 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use 3 A cell of e.m.f. E with an internal resistance r is connected in an electrical circuit consisting four resistors and a resistance wire W as shown below. When the current flowing through the cell is 12.0 A, the potential difference across AC is 6.0 V. (a) 1.875  1019 electrons pass through the cell in t seconds. (i) Show that t = 0 . 2 5 s . [ 1 ] t Ne t QI  (ii) Calculate the amount of electrical energy converted by the cell between the points A and C during this time period.     JxxNeVQVW 186106.110875.1 1919   energy = ………………….. J [1] (b) The resistivity of W is 1.36  10-5 Ω m, its length is 0.5 m, and its diameter is 4.0  10-3 m. Show that the effective re sistance across AC due to the four resistors and W is 0.5 Ω. [3] A r B B E C r 15.0 Ω 5.0 Ω A 10.0 Ω 20.0 Ω W 15.0 Ω B

8 SRJC 2011 9646/Prelim/2011 [Turn Over For Examiner’s Use (c) Calculate, (i) the potential difference across BC. By potential divider principle, VVBC 43.36 51020 1020 1020 1020       [M1] for formula and [A1] for answer potential difference = ………………….. V [2] (ii) the ratio of the cur