2021 JPJC Prelim H2 Physics P3

[Turn over Data READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black pen. 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 one question only. You are advised to spend about one and 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. This document consists of 22 printed pages. [Turn over For Examiner’s Use 1 / 8 2 / 11 3 / 8 4 / 8 5 / 8 6 / 8 7 / 9 8 / 20 9 / 20 Total / 80 JURONG PIONEER JUNIOR COLLEGE JC2 Preliminary Examination 2021 PHYSICS 9749/03 Higher 2 22 September 2021 Paper 3 Longer Structured Questions 2 hours Candidates answer on the Question Paper. No additional Materials are required. Name: _______________________________ Class: ______________

2 2021/JPJC/Prelim/9749/03 Data speed of light in free space 81000.3 c m s–1 permeability of free space 7 0 104   H m–1 permittivity of free space 12 0 1085.8  F m–1    910361   F m–1 elementary charge 191060.1 e C the Planck constant 341063.6 h J s unified atomic mass constant 271066.1 u kg rest mass of electron 311011.9 em kg rest mass of proton 271067.1 pm kg molar gas constant 31.8R J K–1 mol–1 the Avogadro constant 231002.6 AN mol–1 the Boltzmann constant 231038.1 k J K–1 gravitational constant 111067.6 G N m2 kg–2 acceleration of free fall 81.9g m s–2

3 2021/JPJC/Prelim/9749/03 [Turn over Formulae uniformly accelerated motion 2 2 1 atuts  asuv 222  work done on/by a gas VpW  hydrostatic pressure ghp  gravitational potential GM r  temperature / K / C 273.15TT    pressure of an ideal gas 21 3 Nmpc V mean translational kinetic energy of an ideal gas molecule 3 2E k T displacement of particle in s.h.m. txx sin0 velocity of particle in s.h.m. tvv cos0 22 0 xx   electric current AnvqI resistors in series ...21  RRR resistors in parallel .../1/1/1 21  RRR electric potential r QV 04 alternating current/voltage txx sin0 magnetic flux density due to a long straight wire 0 2B d   I magnetic flux density due to a flat circular coil 0 2 NB r  I magnetic flux density due to a long solenoid 0Bn  I radioactive decay )exp(0 txx  decay constant 1 2 ln2 t 

4 2021/JPJC/Prelim/9749/03 Section A Answer all the questions in this section. 1 (a) A buoy is held partially submerged in sea water by a rope anchored to the sea bed as shown in Fig. 1.1. A fifth of the volume of the buoy is above the sea surface. Fig. 1.1 The buoy has volume 27.5 10  m3 and mass 8.0 kg. The mass of the rope may be neglected. The density of sea water is 31.03 10 kg m−3. (i) Explain what is meant by upthrust. ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………………. [1] (ii) Calculate the value of the upthrust U on the buoy. U = ………..…………..…..... N [2] (iii) Show that the tension in the rope is 530 N. [1] sea bed buoy rope sea surface

5 2021/JPJC/Prelim/9749/03 [Turn over (b) Current in the sea water during high tide cause the buoy in (a) to be displaced so that it is fully submerged and the rope makes an angle of 35 ° with the vertical, as shown in Fig. 1.2. Fig. 1.2 (not to scale) The buoy may be considered to be acted upon by four forces, tension T in the rope, a horizontal force D, upthrust U and weight of buoy, W. (i) The force W is shown in Fig. 1.2. On Fig. 1.2, sketch and label the forces T, U and D. [1] (ii) By resolution of forces, determine the magnitude of the force D. D = ………..…………..…..... N [3] sea bed W direction of current 35° sea surface rope buoy

6 2021/JPJC/Prelim/9749/03 2 (a) (i) Define gravitational potential at a point. ……………………………………………………………………………………………… ………………………………………………………………………………...……….. [1] (ii) Use your answer in (i) to explain why gravitational potential near an isolated mass is always negative. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………………. [2] (b) An isolated solid sphere of radius r may be assumed to have its mass M concentrated at its centre. The magnitude of the gravitational potential at the surface of the sphere is ϕ. On Fig. 2.1, sketch the variation of the gravitational potential with distance d from the centre of the sphere for values from d = r to d = 4r. Fig. 2.1 [2] gravitational potential

7 2021/JPJC/Prelim/9749/03 [Turn over (c) The sphere in (b) is a planet with radius r of 6400 km and mass M of 246.0 10 kg . The planet has no atmosphere. A spacecraft of mass 8600 kg is to be put into circular orbit about this planet. It orbits at a distance 4r from the centre of the planet. (i) Show that the speed of the spacecraft at this orbit is 314.0 10 m s  . [2] (ii) The spacecraft then moves to another orbit. Its distance from the centre of the planet changes from 4r to 3r. 1. Calculate the change in gravitational potential energy of the spacecraft. change = ………..…………..…..... J [2]

8 2021/JPJC/Prelim/9749/03 2. By considering changes in gravitational potential energy and in kinetic energy of the spacecraft or otherwise, determine quantitatively whether the total energy of the spacecraft increases, decreases or remains the same. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………….. [2]

9 2021/JPJC/Prelim/9749/03 [Turn over 3 (a) State the first law of thermodynamics. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [1] (b) An adiabatic process is one in which no heat is supplied to or extracted from a system. (i) Determine the change in the internal energy of an ideal gas when the gas expands and does 500 J of work in an adiabatic process. change in internal energy = ......................................... J [1] (ii) Hence, describe how the temperature of the gas in (i) will change at the end of the adiabatic process. ……………………………………………………………………………………………… ………………………………………………………………………………………..... [1] (c) 2.5 mol of an ideal gas in another system is heated up from 300 K to 500 K without any change in volume. The molar heat capacity of the gas is numerically equal to the quantity of thermal energy required to raise the temperature of 1.0 mol of the gas by 1.0 K. (i) Determine the molar heat capacity of the gas. molar heat capacity =