NYJC H1 PHY P2 QP

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME CLASS TUTOR’S NAME PHYSICS 8866/02 Paper 2 Structured questions 20 September 2011 2 hours Candidates answer on the Question Paper. No Additional Materials are required READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer any two 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 Section A 1 2 3 4 5 Section B 6 7 8 Total This document consists of 20 printed pages.

2 NYJC 2011 8866/01/J2PRELIM/11 DATA AND FORMULAE Data speed of light in free space c = 3.00 x 10 8 m s –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 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∆V hydrostatic pressure p = ρgh resistors in series R = R1 + R2 + .... resistors in parallel 1/R = 1/ R1 + 1/R2 + ....

3 NYJC 2011 8866/01/J2PRELIM/11 [Turn over For Examiner’s Use Section A Answer all the questions in this section. 1 (a) Fig 1.1 shows two blocks, P and Q connected by an inextensible cord over a pulley system. The mass of blocks P and Q are m and 5.0 kg respectively. Block P is suspended freely on one end of the cord, while block Q is placed on ramp with rough surface at an angle of inclination of 25 0. Given that block Q is sliding down the ramp with a constant acceleration of 0.50 m s-2 and the frictional force between the ramp and Q is 7.0 N, determine the mass of block P. mass of block P = ………………… kg [2] (b) The cord was cut when block Q is moving at a speed of 0.10 m s -1 and is 1.2 m away from the bottom of the rough ramp, as shown in Fig 1.2. The frictional force opposing the motion of Q increases with its speed. 5.0 kg rough surface Q 25o 1.2 m R 1.0 ms-1 3.0 kg smooth surface m 5.0 kg pulley cord rough surface P Q 25o Fig 1.1 smooth surface Fig 1.2

4 NYJC 2011 8866/01/J2PRELIM/11 For Examiner’s Use (i) Given that the average frictional force on Q after the cord was cut is 10.7 N, calculate average acceleration of Q as it slides 1.2 m to the bottom of the ramp. average acceleration = ………………… m s -2 [1] (ii) Show that the speed of Q as it leaves the ramp is 2.2 m s -1. [1] (c) Block Q continues to move along the smooth horizontal ground until it collides head-on with block R. Block R has a mass of 3.0 kg and a speed of 1.0 m s -1 just before the collision. Given that the collision is perfectly inelastic, determine the direction and speed of R after the collision. direction of R is ………………… speed of R = ………………… m s -1 [3] (d) The duration of collision between Q and R is 30 ms. Calculate the magnitude of the average force exerted on R by Q. average force = ………………… N [1]

5 NYJC 2011 8866/01/J2PRELIM/11 [Turn over For Examiner’s Use 2 (a) Explain the meaning of the terms longitudinal and transverse when applied to a wave. [2] (b) Fig 2.1 shows the wave profile at time t = 0 of a wave with wavelength 2.0 m and speed 20 m s-1 moving along a string. Points X and Y are on the string. (i) Calculate the frequency of the wave. frequency = ……………… Hz [1] (ii) Sketch the variation with time of the displacement of points X and Y for a time interval of 0.2 s. [4] • X Y • direction of wave Fig 2.1 Point X Point Y 0.1 0.1 t /s 0.2 0.2 t /s

6 NYJC 2011 8866/01/J2PRELIM/11 For Examiner’s Use (iii) Calculate the phase difference between points X and Y. phase difference = ……………… rad [1] 3 Fig 3.1 shows a metal wire of weight 0.100 N carrying a current of 5.0 A suspended by two springs having a combined spring constant of 2.50 N m –1. (a) Explain how the tension in the springs may be reduced using a magnet. [2]     (b) If the effective flux density at the wire due to the magnet used is 36 mT and the effective width of the magnet is 20 cm, calculate the change in vertical displacement of the wire.     change in displacement = ……………… cm [3] 5.0 A Fig 3.1

7 NYJC 2011 8866/01/J2PRELIM/11 [Turn over For Examiner’s Use (c) Deduce what will happen if the wire carries a current that changes direction periodically instead. [1]     (d) Power transmission cable carries a current that changes direction periodically in the Earth’s magnetic field. State with reasons if that described in (c) is observed in these cables. [2]   4 (a) State what is meant by the photoelectric effect. [2] (b) A lamp is placed above a metal surface and an electron requires a minimum energy of 2.0 eV before it can be emitted from the metal surface. (i) Calculate the maximum wavelength of the incident photons from the lamp to cause emission of electrons. maximum wavelength = ……………… m [2] (ii) State the component of electromagnetic spectrum which the radiation that is emitted from the lamp belongs to. [1]

8 NYJC 2011 8866/01/J2PRELIM/11 For Examiner’s Use (iii) The metal surface contains atoms of radius 2.0 x 10 -10 m. It may be assumed that the electron can collect energy from a circular area which has a radius equal to that of the atom. The intensity of light is 0.40 W m -2 at the metal surface. Estimate, on the basis of wave theory, the time required for an electron to collect sufficient energy for it to be emitted from the metal. time required = ……………… s [2] (iv) Explain why your answer to (b)(iii) contradicts the observation from photoelectric effect. [1]

9 NYJC 2011 8866/01/J2PRELIM/11 [Turn over For Examiner’s Use 5 According to the U.S. National Electrical Code, copper wire used for interior wiring of houses, hotels, office buildings, and industrial plants is permitted to carry no more than a specified maximum amount of current. The “wire gauge” is a standard method used to describe the diameter of wires. Note that the larger diameter of the wire, the smaller the wire gauge. Fig. 5.1 shows the graph of Imax against the diameter of the gauge. Fig. 5.1 Table 5.2 shows the diameter and resistance of a length of 120m of copper wire for various wire gauges. Wire Gauge Diameter / mm R / Ω (for a length of 120 m) 14 1.63 0.989 12 2.05 0.625 10 2.59 0.392 8 3.26 0.247 6 4.12 0.155 5 4.62 0.123 4 5.19 0.0976 Table 5.2 90 80 70 60 50