WSSS 2007 Prelim P2

Centre Number Index Number Name Class WEST SPRING SECONDARY SCHOOL PRELIMINARY EXAMINATION 2007 PHYSICS PAPER 2 THEORY DATE: 11 / 09/ 2007 DURATION: 1 Hour 45 Minutes READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, name and class on all the work you hand in. Write in dark blue or black pen in the spaces provided on the Question 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. Answer all questions. Write your answers to section A an d to questions 9 and 10 in the spaces provided on the Question paper. Write your answers to Question 11 on the lined pages and, if necessary, continue on the separate answer paper provided. Candidates are reminded that all quantitative answers should include appropriate units. Candidates are advised to show all their working in a clear and orderly manner, as more marks are awarded for sound use of physics than for correct answers. 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 A B Total Thirst for Knowledge O O 5052 / 02 SETTER (S): MR. PRAKASH This Document consists of 16 printed pages and 2 lined pages. [Turn Over]

2 Section A Answer all the questions in this section. 1 Fig. 1.1 shows the speed-time graph for a sma ll balloon initially at rest, then falling vertically through the air and then attaining constant speed. (a)(i) Use Fig. 1.1 to determine the time interval over which the balloon is accelerating. …………………………………………………………………………………….….. [1] (ii) Is the acceleration constant ? Explain your answer. ………………………………………………………………………………….………… …………………………………………………………………………………….……[2] (b) Explain, using the forces acting, the motion of the balloon for the first second a f t e r r e l e a s e . ………………………………………………………………………………………….… ………………………………………………………………………………………….… ………………………………………………………………………………………….… ……………………………………………………………………………………….…[2] For Examiner’s Use Fig. 1.1

3 (c) The mass of the balloon is 60 g. The gravitational field strength is 10 N/kg. (i) Calculate the weight of the balloon, weight =……………………. [1] (ii) State the value of the air resistance on the balloon 1.0 s after release. Ex plain your answer. …..…………………………………………..……………………………………… …………………………………………………….…………………..…………[2] For Examiner’s Use

4 2 A cyclist, together with his bicycle, has a tota l mass of 90 kg and is travelling with a constant speed of 15 m/s on a flat road at A, as shown in Fig. 2.1. He then goes down a small slope to B so descending 4.0 m. Calculate (a) the kinetic energy at A, kinetic energy =……………………. [1] (b) the loss of potential energy between A and B, loss of potential energy =……………………. [1] (c) the speed at B, assuming that all the lost potential energy is transformed into kinetic energy of the cyclist and bicycle. speed =……………………. [3] Fig. 2.1 For Examiner’s Use

5 3 Sebastian holds the loose end of a long rope which is fixed to a post. He moves it up and down at a rate of 20 times every 5 seconds. Each time he moves the rope 15 cm up and 15 cm down from its original rest position. Fig. 3.1 shows the wave moving along the rope. (a) Why is the wave that travels along the rope called transverse wave? ………………………………………………………………………………………….… ……………………………………………………………………………………….…[1] (b) State two other examples of transverse wave. …………………………………………………………………………………….……[1] (c) State the value of the am plitude of the wave. amplitude =……………………. [1] (d) Calculate the frequency of the wave. frequency =……………………. [1] (e) State the value of the wave length of the wave. wavelength =……………………. [1] (f) Calculate the speed of the wave. Speed =……………………. [1] Fig. 3.1 For Examiner’s Use For Examiner’s Use

6 4 Fig. 4.1 shows the virtual image I formed by a converging lens L. (a) By means of a ray diagram, mark and label on Fig. 4.1 the position of the object, O. [3] (b) What happens to the height of the image if the distance of the object from the lens is decreased? ………………………………………………………………………………….………[1] (c) Define the term focal length. ………………………………………………………………………….………………… ………………………………………………………………………………………… [1] (d) Name three characteristics of the image formed if the distance of the object from the lens is equal to 1.7 times the focal length of the lens. ………………………………………………………………………………………… [2] L F Image, I Fig. 4.1 F

7 5 An electrically positively charged sphere C is brought near a small uncharged conducting sphere S suspended as shown in Fig. 5.1. S is first attracted towards C until it touches the surface of C and then repelled to the position shown in Fig. 5.2. (a) On Fig. 5.1 draw the charges induced on sphere S. [1] (b) Explain carefully why S is first attracted towards C. ………………………………………………………………………………………….… ……………………………………………………………………………………….…… ………………………………………………………………………………………….[2] (c) Explain why S is repelled after to uching the surface of C. ……………………………………………………………………………………….…… ……………………………………………………………………………………….…… ……………………………………………………………………………………….…[2] Fig. 5.1 Fig. 5.2 For Examiner’s Use

8 6 Fig. 6.1 shows a schematic di agram of the lighting circuit for street lamps. All 60 lamps are connected in parallel to a 240 V a.c. supply. The resistance of each lamp is 50.0 . The wires connecting the lamps have negligible resistance. (a) Calculate the effective resistance of the 60 lamps. effective resistance =……………………. [2] (b) Calculate the current flowing through one lamp. State the formula you use. current =……………………. [2] (c) Calculate the total current flowing out from the power source. total current =……………………. [1] (d) Calculate the power dissipated by one lamp. State the formula you use. power =……………………. [2] 240 V a.c. supply 1st 2nd 60th 59th 50.0 m 50.0 m Fig. 6.1 For Examiner’s Use

9 7 A potential divider circuit is designed with a t hermistor and a fixed resistor as shown in Fig. 7.1. The thermistor has a resistance of 4 kΩ and 6 kΩ when the temperature of the surrounding is 20 oC and 0 oC respectively. This thermistor has resistance that varies linearly with temperature. The alarm sounds when the output voltage (Vout) is 1.0 V or less. (a) Will the alarm sound when the temperature is at 20 oC? Justify your answer by showing clearly the proper calculations. ………………………………………………………………………………………...… [3] (b) Calculate the resistance of the thermistor at which the alarm is activated. resistance =……………………. [2] (c) Write down the temperature at which the alarm will be activated. Explain your conclusion. …………………………………….……