NYJC 2021 H2 Physics 9749 P2

NYJC 2021 9749/02/J2Prelim/21 [Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS TUTOR’S NAME CENTRE NUMBER S INDEX NUMBER PHYSICS 9749/02 Paper 2 Structured Questions 16 September 2021 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class, Centre number and index number in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. 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. For Examiner’s Use 1 / 8 2 / 8 3 / 8 4 / 10 5 / 10 6 / 10 7 / 6 8 / 20 Total / 80 This document consists of 23 printed pages.

2 NYJC 2021 9749/02/J2Prelim/21 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

3 NYJC 2021 9749/02/J2Prelim/21 [Turn over 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 

4 NYJC 2021 9749/02/J2Prelim/21 1 (a) A body has an initial velocity u and an acceleration a. After a time t, the body has moved a displacement s and has a final velocity v. One of the equations of motion of this body is 21 2s ut at State the conditions that must be satisfied for the above equation to be valid. [2] (b) A hot air balloon is moving at a constant velocity of 11.7 m s-1, at an angle of 59° from the horizontal, as shown in Fig. 1.1 below. Fig. 1.1 (i) Determine the vertical component of the velocity of the balloon. vertical component of the velocity = m s-1 [1] (ii) A slotted mass is released from the balloon. Fig. 1.2 shows the subsequent path of the slotted mass. The dotted figure shows the position of the hot air balloon at the instant when the slotted mass is released. Fig. 1.2 11.7 m s-1 59° slotted mass

5 NYJC 2021 9749/02/J2Prelim/21 [Turn over 1. Throughout the motion, the slotted mass is observed to be directly below the hot air balloon. Explain why this is so. [1] 2. Determine how far below the balloon would the slotted mass be after 3.0 s. You may assume that the slotted mass has not yet landed on the ground and that air resistance on the slotted mass is negligible. distance = m [3] 3. Describe qualitatively the changes, if any, to the answer in (b)(ii)2 if a 100 kg cargo was dropped from the balloon instead of the slotted mass. Assume air resistance on the cargo is negligible too. [1] [Total: 8]

6 NYJC 2021 9749/02/J2Prelim/21 2 (a) State the conditions required for a body to be in equilibrium. [2] (b) Fig. 2.1 shows a lamp weighing 5.0 N that is hung from the end of a beam 4.50 m long and weighing 1.0 N, making an angle of 25° below the horizontal. Fig. 2.1 The beam is held in position by a hinge at its upper end and by a cable 3.00 m lower down the beam and perpendicular to it. The centre of gravity of the beam is 2.00 m along the beam from the hinge. (i) The position of the centre of gravity of the beam is not at its midpoint. Suggest what this implies about the distribution of the mass in the beam. [1] (ii) Show that the tension T in the cable is 7.4 N. taking moments about the pivot 1.00 (2.00 cos 25.0) + 5.00 (4.5 cos 25.0) - (3.00) = 0 = 7.40 N T T [2] ceiling 25° T 5.0 N 1.0 N lamp hinge

7 NYJC 2021 9749/02/J2Prelim/21 [Turn over (iii) Determine the magnitude and the direction of the force acting on the beam at the hinge. y y y Assume the vertical component of the force at the hinge is upwards 7.40cos25.0 1.00 5.00 0 0.707 N F F F      (the minus sign meens that this force is actually acting downwards) Assume the horizontal component of the force at the hinge is to the right 7.40sin25.0 0 3.13 N x x x F F F    22 223.13 0.707 3.21 N xYF F F   Let θ be the angle of F below the horizontal 0.707tan = 3.10 12.8    magnitude = N direction = [3] [Total: 8] 3 The Earth may be assumed to be a uniform sphere of radius R and mass M. At its surface, the gravitational field strength is g. A satellite orbits the Earth at a height 0.30R above its surface. (a) Show that the gravitational field strength at this height is 0.59g. [2] (b) Determine the angular speed of the satellite about the Earth. The radius R of the Earth is 6.4 × 106 m. angular speed = rad s−1 [2]

8 NYJC 2021 9749/02/J2Prelim/21 (c) Calculate the time, in hours, for one complete orbit of the satellite. time = h [2] (d) Explain why the satellite does not fall towards the Earth even though the gravitational force is directed toward the centre of the Earth. [2] [Total: 8] 4 The piston in the cylinder of a car engine is made to move in the cylinder with simple harmonic motion. Fig. 4.1 shows the highest and lowest positions of the piston. Fig. 4.1 highest position lowest position

9 NYJC 2021 9749/02/J2Prelim/21 [Turn over The variation of the acceleration a of the piston with its displacement x from position O is as shown in Fig. 4.2. (a) State and explain the features of Fig. 4.2 that indicate that the motion of the piston is simple harmonic. [2] Fig. 4.2 a / m s-2 x / cm 12000 8000 4000 - 12000 - 8000 - 4000 - 4 - 6 - 2 0 2 4 6

10 NYJC 2021 9749/02/J2Prelim/21 (b) Determine the maxim