42 SMSS Prelim 2011 P2

Name: …………………………………….……….. Reg. No. ………… Class: ………….… Secondary 4 Express 15th September 2011 Duration : 1 hour 45 minutes Total Marks : 80 READ THESE INSTRUCTIONS FIRST Do not open this Booklet until you are told to do so. Write your name, register number and class in the spaces at the top of this page and on any separate writing paper used. Write in dark blue or black pen. 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 all questions. Question 13 has a choice of parts to answer. Write your answers to Section A and to Questions 10,11 and 12 in the spaces provided on the Question Paper. Write your answer to Question 13 on the lined pages and, if necessary, continue on the separate Answer Paper provided. At the end of the examination, fasten all your work securely together. 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. The number of marks is given in brackets [ ] at the end of each question or part question. When necessary, assume the acceleration due to gravity, g to be 10 m/s2. ________________________________________________________________________ This question paper consists of 20 printed pages PHYSICS 5058/02 St. Margaret’s Secondary School Preliminary Examinations 2011 [Turn over

2 Section A Answer all the questions in this section. 1 A police driving test concluded that Sarah has a reaction time of 0.5 s. It was also tested that her car had a deceleration of 5.0 m/s2. a) Sketch the speed-time graph at the instance when she sees the traffic light turning red, assuming that she has to bring her car to rest from the speed of 10 m/s. [2] b) Determine the distance she travelled from seeing the traffic light turning red till it comes to rest from the speed of 10m/s. [2] 2 In May 2006, Singapore first Helium ride, the DHL balloon was launched. Figure 2 shows the schematic diagram of the balloon. The weight of the balloon is 4200 N. The speed at which the balloon drifts up can be controlled by a cable attached to the balloon. The balloon is lifted up by an upthrust created due to the density of helium gas. This upthrust is constant throughout the motion of the balloon. Fig. 2 a) On figure 2, draw and label the arrow to shows the direction of the forces experienced by the balloon. [3] Cable which attacheds the balloon to the ground.

3 b) Find the tension in the cable when the balloon is moving up at constant speed, given that the upthrust is 4800 N. Explain your working clearly. [2] Tension = ………………….. c) How will the effect of wind from the side affect the value of the tension in the cables? [1] ………………………………………………………………………………………………… ……………………………………………………………………………………………….. 3 Fig. 3 shows a bullet of mass 4.20 g travelling towards a wooden barrier 1.00 m thick. It hits the barrier at 1500 m/s. The barrier exerts a constant resistive force of 3000 N on the bullet. Fig. 3 a) Define work done by a force and state the SI unit for work done. [2] …………………………………………………………………………………………….…... ………………………………………………………………………………………………… ………………………………………………………………………………………………… b) Determine the kinetic energy of the bullet just before impact. [1] Kinetic energy = ……………………..

4 c) Calculate the work done by the resistive force on the bullet if the bullet passes through the wooden barrier. [1] Work done = …………………... d) Hence determine whether the bullet passes through the wooden barrier and state a reason. [2] ………………………………………………………………………………………….….….. …………………………………………………………………………………...................... …………………………………………………………………………………...................... e) State the main energy change in the bullet as it travels through the wooden barrier. [1] …………………………………………………………………………………….…………... …………………………………………………………………………………...................... 4 An experiment set-up shown below is used to measure the specific latent heat of vaporization of water. Water in a beaker is kept boiling by an immersion heater which is connected to the main supply through the kilowatt-hour meter. The following data are obtained from the experiment right after the water star to boil: Energy consumed by the heater = 0.128 kWh Initial reading of the electronic balance = 0.846 kg Final reading of the electronic balance = 0.712 kg Heat capacity of the beaker and the heater = 240 J/oC

5 a) Before water starts to boil, the reading of the electronic balance decreases slowly with time. Explain why this happens in terms of the motion of molecules. [2] ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… b) Calculate the specific latent heat of vaporization of water from the data obtained. [2] Latent heat = …………….…… c) Heat loss to the surroundings is one of the major sources of error in this experiment. Give one way heat is lost in this experiment set-up. Suggest a method to reduce the heat lost. [2] ………………………………………………………………………….……………………... ……………………………………………………………………………………….………... …………………………………………………………………………………..................... ………………………………………………………………………………….....................

6 5 The diagram shows a lamp connected in series with an ammeter of negligible resistance. A second identical lamp is connected in parallel across this series arrangement. The lamp circuit is connected in series with a 12 V battery, a switch and a variable resistor. The ammeter reading is 2 A when the voltmeter reading is 5 V. Calculate: a) the resistance of each lamp, [1] Resistance = ……………………… b) the potential difference across the variable resistor. [1] Potential difference = ……………….. c) the current through the variable resistor. [1] current = ……………………..

7 6 Power plug is to be connected to an electric water heater. The three wires in the power plug and the circuit of the heater are shown in Fig. 6. The rating of the heater is ‘240 V 1500 W’ while the rating of the lamp is ‘240 V 50 W’. a) State which wire of the cable should be connected to terminals A, B and C respectively. [2] i) Wire P connected to terminal ____________ ii) Wire Q connected to terminal ____________ iii) Wire R connected to terminal ____________ b) Suggest a purpose of the lamp in the circuit. [1] ………………………………………………………………………………………………… ………………………………………………………………………………………………… c) Now, the heater is plugged into a wall socket and switched on. Calculate the cost of using the heater for 0.50 hours if electricity costs 50 cents per kWh. [2] cost = ………………… d) The water heater is protected by a fuse. Explain how the fuse works. [2] ……………………………………………………….………………………………………... …………………………………………………………………….………………………...... ………………………………………………………………………………….…………….. Wire R Wire P Wire Q Fig. 6 fuse

8 7 The diagram below shows a simple circuit of an electric bell. Explain how the electric bell works by referring to the diagram below. [3] ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………………