2021 JPJC Prelim H2 Physics P2

2019/JPJC/PHYSICS/9749 [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. Answer all questions. 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 21 printed pages. [Turn over For Examiner’s Use 1 / 12 2 / 10 3 / 10 4 / 12 5 / 8 6 / 8 7 / 20 Total / 80 JURONG PIONEER JUNIOR COLLEGE JC2 Preliminary Examination 2021 PHYSICS 9749/02 Higher 2 14 September 2021 Paper 2 Structured Questions 2 hours Candidates answer on the Question Paper. No additional Materials are required. Name: _______________________________ Class: ______________

2 2021/JPJC/Prelim/9749/02 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 31 e 9.11 10m  kg rest mass of proton 27 p 1.67 10m  kg molar gas constant 31.8R J K–1 mol–1 the Avogadro constant 23 A 6.02 10N  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/9749/02 [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/9749/02 50 cm Answer all questions in the spaces provided 1 An object of mass 350 g is released from rest at a height of 50 cm on a frictionless incline as shown in Fig. 1.1. The incline makes an angle of 30° to the horizontal. It is placed on a table of height 2.0 m above the smooth ground. The table is fixed to the ground. Fig. 1.1 (a) Show that the acceleration of the object is 4.9 m s−2 as it slides down the incline. [1] (b) Determine the speed of the object as it leaves the incline. speed = ........................................ m s−1 [3] incline 2.0 m 30° object table smooth ground

5 2021/JPJC/Prelim/9749/02 [Turn over (c) The object lands on the ground after falling off the incline. Calculate the horizontal distance of the object from the edge of the table. distance = ........................................... m [3] (d) A small trolley of mass 1.2 kg is moving to the left at a speed of 4.0 m s −1 along the smooth ground. The object is released again from the same height on the incline. It lands in the trolley and they move off together horizontally. (i) Explain whether momentum of the system of object and trolley is conserved in the horizontal direction. .................................................................................................................................. .................................................................................................................................. ……………………………………………………………………………………………… …………………………………………………………………………………………. [2] (ii) Hence, calculate the final velocity of the trolley and object. magnitude of velocity = ........................................ m s−1 direction = ............................................... [3]

6 2021/JPJC/Prelim/9749/02 2 (a) The pressure p of an ideal gas of density  is related to the mean square speed 2c of its molecules by the expression 21 3pc    . Show that the average kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature T. [3] (b) A scuba tank for a diver has a volume of 339.4 10 cm and when the tank is filled, the air has a pressure of 72.32 10 Pa at a temperature of 24 °C. The diver is swimming in water of density 331.03 10 kg m  and temperature 24 °C at a depth of 15 m. When the diver breathes in, the pressure of the air delivered from the tank to the diver is always equal to the pressure of the surrounding water. Atmospheric pressure is 51.01 10 Pa . Air may be considered as an ideal gas. Calculate, for the depth of 15 m, (i) the total pressure on the diver, total pressure = ......................................... Pa [2]

7 2021/JPJC/Prelim/9749/02 [Turn over (ii) the volume of air available at this pressure from the tank. volume = ......................................... cm3 [2] (c) The supply of air in (b) is sufficient for the diver to remain at a depth of 15 m for 45 minutes. Assuming that the diver always breathes at the same rate regardless of the pressure, determine how long the air in the tank will last for the diver at a depth of 35 m and a water temperature of 19 °C. time = ......................................... min [3]

8 2021/JPJC/Prelim/9749/02 3 Fig. 3.1 shows a pair of identical loudspeakers A and B placed 2. 0 m apart and emitting coherent so und waves of frequency 470 Hz. An observer walks from X to Y. The perpendicular distance be tween the sources and XY is 12 m. As he walks, he hears a sound of maximum intensity at P, followed by minimum intensity at Q and th e next maximum intensity at R. P is equidistant from A and B. R is 4.5 m away from P. Fig. 3.1 (a) Explain how minimum intensity of sound is formed along the line XY. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [2] (b) (i) Show that BR is 13.2 m. [1] (ii) AR is 12.5 m. Determine the wavelength of the sound. wavelength = ........................................ m [2] 12 m 2.0 m 4.5 m

9 2021/JPJC/Prelim/9749/02 [Turn over (iii) Determine the speed of the sound. speed = ........................................ m s–1 [2] (c) The sound reaching Q from A alone has intensity I and that from B alone has intensity 3 I . Determine the intensity at Q in terms of I. intensity = ........................................ I [3]

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