Evaluate — 4 marks
A theme park is designing a new roller coaster. Engineers must choose between two braking systems for the final descent: System A uses friction brake pads that convert kinetic energy directly to heat, while System B uses regenerative electromagnetic brakes that convert kinetic energy into electrical energy stored in a battery. Both systems must safely stop a 500 kg carriage travelling at 20 m/s within 50 m.
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(a) Calculate the kinetic energy of the carriage before braking begins.
[1 mark]
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(b) System A converts all kinetic energy to thermal energy in the brake pads. Explain why this system might be considered wasteful from an energy conservation perspective.
[1 mark]
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(c) Evaluate the advantages and disadvantages of System B (regenerative braking) compared to System A for use on a theme park roller coaster. Consider both energy efficiency and practical factors.
[2 marks]
Show mark scheme
- (a) Correct calculation: KE = ½mv² = ½ × 500 × 20² = 100,000 J (or 100 kJ) (1 mark)
- (b) The energy is dissipated/lost as heat to the surroundings rather than being stored or reused, so it cannot be recovered for other purposes (1 mark)
- (c) Advantage: System B stores electrical energy in the battery which can be reused to power the ride or other park systems, improving overall energy efficiency / less energy is wasted (1 mark)
- (c) Disadvantage: System B is more complex/expensive to install and maintain; the battery has limited capacity so may not store all the energy; electromagnetic brakes may be less reliable in extreme weather; friction brakes provide more predictable, consistent stopping performance (accept any one practical disadvantage) (1 mark)
Show — 2 marks
A student drops a rubber ball from a height of 2 metres onto a hard floor. The ball bounces back up to a height of 1.5 metres. Some energy is lost during the collision with the floor.
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(a) Show that the ball loses gravitational potential energy as it falls from 2 m to the floor.
[1 mark]
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(b) Explain why the ball does not bounce back to its original height of 2 metres.
[1 mark]
Show mark scheme
- (a) As the ball falls, height decreases, so gravitational potential energy (Ep = mgh) decreases / energy is converted to kinetic energy as the ball accelerates downwards
- (b) Energy is dissipated/lost as heat, sound and deformation during the collision with the floor / not all kinetic energy is converted back to gravitational potential energy / some energy is wasted
Calculate — 2 marks
A student investigates the energy transfers in a filament lamp. The lamp is switched on for one minute. During this time, 3000 J of electrical energy is supplied to the lamp. Of this energy, 2700 J is transferred to the surroundings as thermal energy.
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(a) Calculate the amount of useful light energy transferred by the lamp.
[1 mark]
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(b) Calculate the efficiency of the lamp.
[1 mark]
Show mark scheme
- (a) 300 (J) or 3000 – 2700
- (b) 10% or 0.1 or correct calculation using their answer from 01.1
Explain — 3 marks
A student drops a basketball from a height of 1 metre. The ball bounces on the floor several times, with each bounce lower than the one before. Eventually, the ball stops moving.
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(a) State the main energy store of the ball just before it is released.
[1 mark]
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(b) Explain why the ball does not bounce back up to its original height of 1 metre.
[2 marks]
Show mark scheme
- (a) Gravitational potential energy (store)
- (b) Energy is transferred to the surroundings / thermal energy store (of ball, floor, air)
- (b) Energy is also transferred to the sound energy store / dissipated
Describe — 2 marks
A student drops a rubber ball onto a hard floor. The ball bounces several times, with each bounce reaching a lower height than the previous one, until the ball eventually comes to rest on the floor.
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(a) Describe what happens to the total kinetic and potential energy of the ball after each bounce.
[1 mark]
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(b) Describe what happens to the energy that is 'lost' from the ball as it bounces.
[1 mark]
Show mark scheme
- (a) Total kinetic and potential energy decreases (after each bounce)
- (b) Dissipated/transferred to surroundings as thermal energy/heat
- (b) OR dissipated/transferred to surroundings as sound
GCSE Perfect