TJC 2022 Prelim P2

TEMASEK JUNIOR COLLEGE 2022 JC2 Preliminary Examination Higher 2 NAME CG PHYSICS Paper 2 Structured Questions 9749/02 23 August 2022 2 hours For Examiner’s Use READ THESE INSTRUCTIONS FIRST 1 Write your name and civics group in the spaces at the top of this page. 2 Write in dark blue or black pen on both sides of the paper. 3 You may use an HB pencil for any diagrams or graphs. 4 Do not use staples, paper clips, glue or correction fluid. 5 The use of an approved scientific calculator is expected, where appropriate. 6 Answer all questions 7 s.f The number of marks is given in brackets [ ] at the end of each question or part question. Total This booklet consists of 20 printed pages

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 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 o = 8.85 x 10-12 F m-1 or (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 Js 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 + ½ at2 v2 = u2 + 2as work done on/by a gas W = p ΔV hydrostatic pressure p = gh gravitational potential  = –Gm/r temperature T/K = T/oC + 273.15 pressure of an ideal gas p = 3 1 V Nm < c2 > mean translational kinetic energy of an ideal gas molecule E = 2 3 kT displacement of particle in s.h.m. x = xosint velocity of particle in s.h.m. v = vocost = )( 22 xxo −  electric current I = Anvq resistors in series R = R1 + R2 + .... resistors in parallel 1/R = 1/R1 + 1/R2 + .... electric potential V = rε4π Q o alternating current/voltage x = xo sint magnetic flux density due to a long straight wire B = 𝜇𝑜𝐼 2𝜋𝑑 magnetic flux density due to a flat circular coil B = 𝜇𝑜𝑁𝐼 2𝑟 magnetic flux density due to a long solenoid B = onI radioactive decay x = x0 exp(−t) decay constant λ = 𝑙𝑛2 𝑡1/2

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 3 [Turn over Answer all the questions in the spaces provided. 1 A propeller driven boat of mass 800 kg is traveling in still water in a straight line. When the boat is moving at a constant speed of 15 m s-1, the power delivered to the propeller is 90 kW. (a) Calculate the total resistive force on the boat. total resistive force = N [2] (b) If the power delivered is then suddenly increased to 120 kW, determine the initial acceleration of the boat. initial acceleration = m s-2 [2] (c) Explain how the acceleration will vary over time as the power is maintained at 120 kW. [4]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 4 2 (a) A star and a planet orbit their mutual centre of mass as shown in Fig. 2.1. The diagram is not to scale. Fig. 2.1 (i) Calculate the distance of the centre of mass from the centre of the star. Explain your working clearly. distance = m [2] (ii) Calculate the period of orbit. period = s [2]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 5 [Turn over (iii) Astronomers note a periodic dip in the brightness of the star as shown in Fig. 2.2. Fig. 2.2 Explain this observation. [1] (b) The satellite NOAA-20 was launched in November 2017. The satellite has an approximately circular orbit at an altitude of 825 km above the Earth’s surface. The radius of the Earth = 6.4 × 106 m. Fig. 2.3 shows how the gravitational field strength g of the Earth varies with distance r from the centre of the Earth. Fig. 2.3

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 6 (i) The mass of the satellite is 2300 kg. Use the graph to show that the change in gravitational potential energy of the satellite between its launch and its position in orbit is about 1.6 ×1010 J. Explain your working clearly. [3] (ii) Use the value for the change in potential energy from (b)(i) to determine the mass of the Earth. mass of Earth = kg [2] (iii) The satellite takes a polar orbit, revolving around the Earth from pole to pole, as shown in Fig. 2.4. Geostationary satellites orbit at a greater distance from the Earth. Fig. 2.4

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 7 [Turn over Explain why a low, polar orbit is useful for satellites used for weather forecasting and suggest why geostationary satellites are used for telecommunications [2] 3 A diffraction grating is set up at the centre of a rotating table which completes a revolution in every 3.0 s. The grating is illuminated normally by monochromatic light of wavelength λ from a source which is also mounted on the table as shown in Fig. 3.1. Fig. 3.1 The emergent beams of light from the grating are monitored by means of a stationary detector. The output from the detector is displayed on a cathode ray oscilloscope (c.r.o.). With the time-base set at 0.10 s cm-1, the trace obtained is shown in Fig. 3.2. The relative positions of the peaks are as indicated. Fig. 3.2 Top view

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 8 (a) Calculate the angular speed of rotation of the grating. angular speed = rad s-1 [1] (b) Explain why the peaks in Fig. 3.2 do not have the same intensity. [2] (c) (i) If θ is the angle between the emergent ray and the normal. Use your answer in (a), determine θ for peak E. θ = radian [2] (ii) Using peak E, hence calculate the wavelength of the light if the grating has 550 lines per mm. wavelength = nm [2] (iii) Explain why 1. it is preferable to calculate the wavelength using peak E rather than peak D. [1]

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9 [Turn over 2. only 5 peaks are observed with some calculations. [2] (d) Sketch, in Fig. 3.2, the trace on the c.r.o, if the diffraction grating is replaced by a double slit of the same slit separation and slit width as the diffraction grating. [1] 4 The variation with potential difference V of current I for a light emitting diode (LED) is shown in Fig. 4.1. Fig. 4.1 (a) (i) Use Fig. 4.1 to determine the resistance of the LED at 2.25 V. resistance = Ω [1] I/ mA V/ V

DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 10 (ii) Shade in Fig. 4.1 the area that represent the increase in power dissipation in the LED if the potential difference across the LED is increased from 1.50 V to 1.75 V. [1] (b) Two of these LEDs are connected to a 3.0 V battery with negligible internal resistance and a 160 Ω