2024 NYJC H2 PHY 0749 P1 Answers

NYJC 2024 9749/01/J2Prelim/24 [Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS TUTOR’S NAME CENTRE NUMBER S INDEX NUMBER PHYSICS 9749/01 Paper 1 Multiple Choice 17 September 2024 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, class, Centre number and index number in the spaces at the top of this page. 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 Answer Sheet. Read the instructions on the Answer Sheet 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. This document consists of 15 printed pages. H SOLUTION

2 NYJC 2024 9749/01/J2Prelim/24 Data speed of light in free space c = 3.00 × 108 m s−1 permeability of free space  = 4 × 10−7 H m−1 permittivity of free space  = 8.85 × 10−12 F m−1 (1 / (36)) × 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 21 2s ut at=+ 22 2v u as=+ work done on / by a gas W p V= hydrostatic pressure p gh= 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 molecule 3 2E kT= displacement of particle in s.h.m. 0 sinx x t = velocity of particle in s.h.m. 0 cosv v t = 22 0xx=  − electric current =I Anvq resistors in series 12 . . .R R R= + + resistors in parallel 121/ 1/ 1/ . . .R R R= + + electric potential 04 QV r= alternating current/voltage 0 sinx x t = magnetic flux density due to a long straight wire  = 0 2 IB d magnetic flux density due to a flat circular coil = 0 2 NIB r magnetic flux density due to a long solenoid = 0B nI radioactive decay 0 exp( )x x t =− decay constant 1 2 ln2 t =

3 NYJC 2024 9749/01/J2Prelim/24 [Turn over Answer all questions. 1 The base units of the SI system include those of The base units of the SI system include those of mass, kg; length, m; time, s; electric current, A. Which base units would be needed to express the SI unit of potential difference (the volt)? A m and A only. B s and A only. C m, s and A only. D kg, m, s and A. 2 A car travelling at a speed of 15.0 m s−1 can be brought to rest in 1.20 s when a uniform braking force is applied. The reaction time of the driver is 0.100 s. What is the minimum distance at which the driver must notice a stationary object in order to avoid hitting it? A 1.50 m B 7.50 m C 9.00 m D 10.5 m Ans: D 2kg ms m A s W Fs masV Q t t −  = = = = II Ans: D ( ) -2 2 2 2 15.00 15.0 m s 1.20 15.00 15.0 9.00 m 1.20 1.20 22 v u at a a sv u as s = +  = +  = −  =  = = + + −  Thinking distance = 15.0 m s−1  0.100 s = 1.50 m Minimum distance = 1.50 + 9.00 = 10.5 m

4 NYJC 2024 9749/01/J2Prelim/24 3 Ball P is projected upwards from the bottom of a smooth inclined plane with an initial speed that is just sufficient for it to reach the top of the plane. At the same time that Ball P is projected, Ball Q is projected downwards from the top of the plane with the same initial speed as Ball P. What is the ratio of the distance travelled by Ball 2 to the distance travelled by Ball 1 when they collide? A 0.78 B 1.0 C 1.3 D 3.0 Ans: C From 1 21s ut at 2=− and 2 21s ut at 2=+ , where a = g sin   12 2s s ut+= (1) From v2 = u2 − 2as,  12 2uss 2a+= (2) From (1) & (2), 2 4 2uut 2a ut a = = 9 4 8 137 84 2 2 21 1u1 uaut ats 2a2 .1 1us ut at ua2 2a ++ = = = = − −  Ball P Ball Q

5 NYJC 2024 9749/01/J2Prelim/24 [Turn over 4 The rate of change of momentum experienced by a free -falling ball when it hits the ground is equal to A its weight. B the net force acting on it. C the force exerted on it by the ground. D the impuse on the ball due to the ground. 5 The diagram shows a woman standing in a lift. The forces acting on the woman and the forces acting on the lift are shown. Which statement is correct? A N and W1 are always equal and opposite. B (W1 + W2) is always equal to T. C If N = W1, the lift must be at rest. D If T = (D + W2), the lift must have a constant velocity. Ans: B By Newton’s second law.

6 NYJC 2024 9749/01/J2Prelim/24 6 A cylindrical drum has radius r and weight W. The drum is to be rolled over onto a step of height r 2 by a horizontal force F applied to the top of the drum. What is the minimum force F required for the drum to start rolling on the step? A W 2 B W 3 C W D W3 2 Ans: D Ans: B Taking moments about the step, 3 222 3 2 3 2 3 rW r F r Wr F r W  =−    = =

7 NYJC 2024 9749/01/J2Prelim/24 [Turn over 7 A ball of mass m falls freely from rest as shown below. When it has reached a speed v, it just strikes a vertical spring. The spring is then compressed by a distance y before the ball moves upwards again. Assumes that all the energy the ball loses becomes elastic potential energy in the spring. What is the average force exerted by the spring during its compression. A mv y 2 2 B m v gyy 2( 2 )2 − C mv y 2 D m v gyy 2( 2 )2 + 8 The driver of a 1000 kg car tries to turn through a circle of radius 100 m on an unbanked curve at a speed of 10 m s−1. The maximum frictional force between the tyres and the slippery road is 900 N. The car will A Slide into the inside of the curve. B Make the turn. C Slow down due to the centrifugal force. D Slide off to the outside of the curve. Ans: D ave Fy mv mgy mv mgy FF y 2 2 11 22 1 1 2 2 =+ + == Ans: D Centripetal force required, Fc = mv2/r = 1000(102)/100 = 1000 N The maximum frictional force between the tyres and the slippery road is 900 N, which is insufficient to allow the car to turn around. Hence, the car will slide off to the outside of the curve.

8 NYJC 2024 9749/01/J2Prelim/24 9 A simple pendulum consists of a bob of mass m at the end of a light and inextensible thread of length L. The other end of the thread is fixed at C. The bob swings through point B with velocity v and just reaches A, where the string is just taut. What is the tension in the thread as the bob passes point B? A mg B 2mg C 3 mg D 4 mg 10 An object X has weight W on the surface of the Earth. How much energy is needed to raise X to height of 2R above the surface of the Earth, where R is the radius of the Earth? A 1 3 WR B 2 3 WR C 3 2 WR D 2WR Ans: C ( ) 22 2 2 2 s in 1 [ 0]2 1 2 2 2 3mg in AA gain GPE los KE mgL m v v v mgL mv mv mgL mv mgLT mg LL T = = − = = = − = = = Ans: B W = 2 GMm R Increase in GPE = − 3 GMm R − (− GMm R ) = 2 3 GMm R = 2 3 WR B C L v A

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