Evaluate — 4 marks
A student investigates energy changes in a system by dropping a rubber ball from a height of 2.0 m onto a hard floor. The ball bounces back to a height of 1.4 m on the first bounce. The student claims that energy is not conserved in this system because the ball does not return to its original height.
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Calculate the percentage of gravitational potential energy lost during the first bounce. (Assume g = 10 m/s²)
[1 mark]
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Evaluate the student's claim that energy is not conserved in this system. In your answer, explain what happens to the 'missing' energy and identify the type of energy transformation that occurs.
[2 marks]
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The student repeats the experiment with a tennis ball dropped from the same height. The tennis ball bounces to only 0.8 m. Suggest why the tennis ball loses a greater percentage of its energy than the rubber ball, and explain whether this observation supports or contradicts the principle of conservation of energy.
[1 mark]
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Describe — 3 marks
A student is investigating energy changes by dropping a rubber ball from a height of 2 metres onto a hard floor. The ball bounces several times before coming to rest on the ground.
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Describe the energy change that occurs as the ball falls from the height of 2 metres towards the floor.
[1 mark]
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Describe what happens to the energy when the ball hits the floor and bounces back up.
[1 mark]
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Describe why the ball eventually comes to rest on the ground, in terms of energy changes in the system.
[1 mark]
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Calculate — 2 marks
A student uses an electric kettle to heat water for a hot drink. The kettle has a power rating of 2400 W and is switched on for 45 seconds. The student wants to understand the energy changes involved in heating the water.
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Calculate the total electrical energy supplied to the kettle. Give your answer in joules (J).
[1 mark]
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If 85% of the electrical energy is transferred to the water as thermal energy, calculate the thermal energy gained by the water.
[1 mark]
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Suggest — 2 marks
A student is investigating energy changes when a ball is dropped from different heights onto a concrete floor. The ball bounces to different heights each time it is dropped. The student notices that the ball becomes slightly warmer after being dropped multiple times.
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Suggest why the ball becomes warmer after being dropped multiple times.
[1 mark]
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Suggest why the ball does not bounce back to its original height after each drop.
[1 mark]
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Define — 2 marks
A student is investigating energy changes in a system by dropping a ball from different heights onto a force plate connected to a motion sensor. The ball bounces to different heights depending on the initial drop height. The student needs to understand how energy is transferred and transformed during this process.
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Define what is meant by a 'closed system' in the context of the bouncing ball experiment.
[1 mark]
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Define the term 'energy dissipation' and identify one way energy is dissipated when the ball bounces.
[1 mark]
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GCSE Perfect