NJC H2 Physics Prelim P1 Ans

1 [Turn over NATIONAL JUNIOR COLLEGE SENIOR HIGH 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet 9749/01 15 September 2023 1 hour READ THE INSTRUCTION FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, subject class and registration number on the Optical Answer Sheet (OAS) in the spaces provided. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate OAS. Read the instructions on the OAS very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. Shading of OAS index number OAS index number is in a 5-digit format. The 5 digit format is as follows: 1st digit and the last four digits of the Reg Number. e.g. 2005011 becomes 25011 This document consists of 19 printed pages and 1 blank page.

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4 [Turn over 1 Which definition is correct and uses only quantities rather than units? A Density is mass per cubic metre. B Potential difference is energy per unit current. C Pressure is force per unit area. D Speed is distance travelled per second. Ans: C 2 Which formula could be correct for the speed v of ocean waves in terms of density  of sea- water, the acceleration of free fall g, the height h of the wave and the wavelength ? A v = √gh B v = √g h C v = √g D v = √ g  2 C unit of √g = √(m s-2) m = m s−1 3 A ball, initially at rest, is dropped in the air from a great height. Air resistance is not negligible. Which of the following graphs best shows the variation with time t of the acceleration a of the ball? A B C D 3 C mg – kv =ma As time increases, a drops. Since v is not linear with time because acceleration is not constant therefore must be C

5 [Turn over 4 A lift consists of a passenger car supported by a cable which runs over a light, frictionless pulley to a balancing weight. The balancing weight falls as the passenger car rises. (not drawn to scale) The masses are shown in the table. mass / kg passenger car 1200 balancing weight 1320 passenger 80 What is the magnitude of the force between the passenger and the passenger car when carrying just one passenger and when the pulley is free to rotate? A 12 N B 773 N C 785 N D 797 N 4 D for inextensible cable, the passenger, passenger car and balancing weight moves as one object with the upward motion of the balancing weight equivalent to the downward motion of the passenger and passenger car 1320 × 9.81 − (1200+80) × 9.81 = (1320+1200+80) a a = 0.15092 m s−2 resultant force on passenger = 80 × 0.15092 = 12.074 N upwards force by passenger car on passenger − weight of passenger = 12.074 N force by passenger car on passenger = 12.704 + 80 × 9.81 = 797 N balancing weight passenger car

6 [Turn over 5 A heavy uniform beam of length L is supported by two vertical cords as shown. What is the ratio T1 T2 of the tensions in these cords? A 1 3 B 1 2 C 2 1 D 3 1 5 A Taking pivot about centre of gravity: T1 × ½ l = T2 × 1/6 l T1 / T2 = 1/6 l / ½ l = 1/3 6 A constant force is applied to a body which is initially stationary but free to move in the direction of the force. Assuming that the effects of friction are negligible, which of the following graphs best represents the variation with time t of the power supplied P? A B C D t P 0 t P 0 t P 0 t P 0

7 [Turn over 6 B As force is constant, acceleration on the body is constant, but velocity is increasing at a constant rate. (v = u + at), hence, the power = Fv is increasing at a constant rate. 7 A turntable has radius R. It is driven by a rubber drive wheel of radius r in contact with the inside of the rim of the turntable, as shown below. plan view The turntable rotates with angular velocity  and the linear speed of a point on its rim is V. The drive wheel rotates with angular velocity  and the linear speed of a point on its rim is v. Which pair of equations show the relationship between the angular velocities and the linear speeds of the turntable and the wheel? angular velocities linear speeds A  =  V = v B  =  V = ( r R ) v C  = ( r R )  V = v D  = ( R r )  V = ( r R ) v 7 C Since no change in linear displacement, the 2 linear velocities are the same R  = r 

8 [Turn over 8 The graph below shows the variation with distance x of the displacement y of a transverse wave at a particular instance in time. A second transverse wave has the same amplitude , twice the speed and twice the frequency. For the second wave, which of the graphs below shows the variation with distance x of its displacement y? A B C D y / cm 2.0 0 − 2.0 x / m 0.2 0.4 2.0 0 −2.0 y / cm x / m 0.2 0.4 y / cm 2.0 0 −2.0 x / m 0.2 0.4 y / cm 2.0 0 −2.0 x / m 0.2 0.4 4.0 0 − 4.0 y / cm x / m 0.2 0.4

9 [Turn over 9 The needle of a sewing machine is made to oscillate vertically through a total distance of 22 mm, as shown below. The oscillation is simple harmonic with a frequency of 4.5 Hz. The cloth that is being sewn is positioned 8.0 mm below the point of the needle when the needle is at its maximum height. What is the speed of the needle as its tip touches the cloth? A 0.00317 m s−1 B 0.0848 m s−1 C 0.226 m s−1 D 0.299 m s−1 9 D Amplitude, x0 = 22/2 = 11 mm When the tip of the touches the cloth, the displacement of needle from the equilibrium position is 3 mm. v =  = (2 (4.5))(√(11 × 10-3)2 − (3 × 10-3)2 = 0.299 m s−1 22 o -xx

10 [Turn over 10 A particle of mass 5.0 kg moves with simple harmonic motion and the variation with position x of its potential energy U is shown below. What is the period of oscillation of the mass? A 7.9 s B 8.8 s C 11 s D 20 s 10 A KEmax = Umax = 1.0 ½ mvmax2 = 1.0 vmax = 0.632 vmax = ωxo = xo T = 2ð 0.8 0.632 x = 7.9 s 11 A double star system is at a distance of 1.9 × 1017 m from the Earth. A telescope with a diameter of 3.0 m is used to view the stars. What is the approximate minimum separation between the two stars of the double star system such that both stars can be detected by the telescope? A 5.0 × 108 m B 1.0 × 109 m C 3.0 × 1010 m D 3.0 × 1011 m 11 C 𝜃 ≈ 𝜆 3 ≈ 𝑥 1.9 × 1017 If violet light: 𝑥 ≈ 400×10−9 3 × 1.9 × 1017 = 2.5 × 1010 m If red light: 𝑥 ≈ 700×10−9 3 × 1.9 × 1017 = 4.4 × 1010 m Since wavelength of visible light must be between wavelength of violet light and wavelength of red light, answer must be between 2.5 and 4.4 ×1010 m 12 The diagram below represents equipotential lines of a gravitational field. U / J x / m - 0.4 0 0.4 0.8 - 0.8 1.0 0.8 0.6 0.4 0.2