Fig.1.1 (a) (i) State the law of conservation of energy...

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1 PAPER 2 THEORY QUESTIONS 1 A falling metal hammer is used to drive a hollow steel post into the ground, as shown in Fig The hammer is lifted by an electric motor and then falls freely to hit the baseplate. Fig.1.1 (a) (i) State the law of conservation of energy. (ii) State the energy conversions that take place as the hammer falls, starting from the initial potential energy of the hammer before it is dropped. (b) The metal hammer has a mass of 1500 kg and it hits the baseplate with a speed of 8.0 m/s. (i) Calculate the kinetic energy of the hammer as it hits the baseplate. kinetic energy =. (ii) State the initial potential energy of the hammer. (iii) Calculate the height above the baseplate from which the hammer is dropped. Take g as 10 N/kg. height =. (c) (i) In raising the hammer, the electric motor uses more energy than that stated in (b)(ii). State and explain two reasons why the motor uses more energy. (ii) State one change to the equipment in Fig. 1.1 that would cause the baseplate to move further into the ground each time the hammer falls.. MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 1

2 2 Fig. 2.1 illustrates the journey of a cyclist from point A to point B. Points A and B are at the same height.. Fig. 2.1 The cyclist starts from rest at A and pedals up and over a hill. Near the bottom of the hill, she starts to brake and comes to rest at B. (a) Describe the energy changes that take place as she pedals up the hill at constant speed [3] (b) Explain how the law of conservation of energy applies to the complete journey from A to B [1] (c) At one point in the journey, the gravitational potential energy of the cyclist has increased by 5400 J. The mass of the cyclist is 60 kg. The gravitational field strength is 10 N / kg. Calculate the height above A of the cyclist at this point. height above A =...[2] 3 Fig. 3.1 is a block diagram of a power station. The four boxes represent different parts of the power station. The first box is labelled boiler. Fig. 3.1 Each of the other three boxes should contain one of the labels from the following list. generator, motor, transformer, turbine, solar panel (a) On Fig. 3.1, label the boxes using words from the list. [2] (b) State one environmental problem caused by burning oil to produce electricity [1] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 2

3 (c) Oil is a non-renewable energy source. (i) State why oil is described as a non-renewable energy source.... [1] (ii) State one renewable energy source.... [1] 4 A coal-fired power station produces electricity by burning coal. Fig. 4.1 shows the block diagram of the power station. Fig. 4.1 (a) Each of the boxes should contain one of the three labels turbine, generator or boiler. (i) Copy the block diagram in Fig. 4.1 and label the boxes. (ii) Describe the useful energy changes that occur in each box of the block diagram. (iii) Burning coal can cause problems in the area around the power station. State one of these problems.... [5] (b) Coal is a non-renewable source of energy. (i) Explain what is meant by non-renewable. (ii) State two other non-renewable sources of energy. (iii) State two renewable sources of energy.... [5] (c) A power station provides 300 kw of electrical power and wastes 900 kw as thermal energy produced in its operation. (i) Calculate the efficiency of the power station. State clearly the equation that you use. efficiency =.. MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 3

4 (ii) Calculate the electrical energy output from the power station in one hour. State clearly the equation that you use and give your answer in joules. energy = [5] 5 Fig. 5.1 shows a hydroelectric power station. Water from the lake is used to produce electricity in the turbine house. Fig. 5.1 (a) State where the water in Fig. 5.1 has the least potential energy... [1] (b) In 30 minutes, the water loses J of energy and J of electrical energy is produced in the turbine house. (i) Calculate the efficiency of the energy conversion. (ii) Calculate, in watts, the electrical power output from the turbine house. efficiency =... [1] power =... W [3] (c) Some power stations burn coal to produce the same electrical power output. State one advantage of the hydroelectric power station [1] (d) State one harmful effect that the hydroelectric power station may have on the environment [1] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 4

5 6 Fig. 6.1 shows the horizontal forces as a cyclist travels forwards. Fig. 6.1 (b) The total mass of the bicycle and the cyclist is 75 kg. At one instant, the speed of the bicycle is 4.0 m / s, the driving force is 30 N and the air resistance is 20 N. Calculate (i) the total kinetic energy of the bicycle and the cyclist, (ii) the acceleration of the bicycle and the cyclist. kinetic energy =...[3] acceleration =...[2] (c) As the bicycle moves, energy is transmitted from the pedals to the back wheel. Fig. 6.2 shows what happens to the energy input to the pedals. Fig. 6.2 (i) As energy is transmitted to the back wheel, some is lost. Explain how this happens.... [2] (ii) Calculate the efficiency of the bicycle in transmitting energy from the pedals to the back wheel. efficiency =...[2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 5

6 7 Fig. 7.1 shows a boat stationary in still water in a narrow tunnel. Fig. 7.1 To move the boat, two men lie on the top of it and push against the tunnel roof with their legs. They exert a total forwards force of 1680 N on the boat. (a) The men push the boat 50.0 m to the end of the tunnel. Calculate the work done on the boat by the men. work done =... [2] (b) Explain why the kinetic energy of the boat at the end of the tunnel is less than the work done on the boat by the men [2] 8 A student carries out an experiment to measure the power he produces. He runs up a flight of stairs, as shown in Fig Fig. 8.1 The student takes readings to calculate his power. (a) (i) List all of the readings he must take.... [3] (ii) State one precaution he should take to make sure one of his readings is accurate.... [1] (b) Write down all of the equations he must use to calculate his power from the readings. You may use symbols or words in your equations [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 6

7 9 Fig. 9.1 shows a motor used to operate a lift (elevator). There is a man in the lift. The input power to the motor is 6200 watts. Fig. 9.1 (a) Define the watt [2] (b) The lift and the man have a total mass of 580 kg. The lift moves up a distance of 12 m in 15 s. (i) Calculate the tension in the cable when the lift is moving at constant speed. (ii) Calculate the increase in potential energy of the lift and man. tension =... [1] (iii) Calculate the efficiency of the motor. potential energy =... [2] efficiency =... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Energy 7