A student drops a rubber ball from a height. The ball bounces several times before eventually coming to rest on the floor. Explain the energy stores and transfers involved from the moment the ball is released until it comes to rest.

OCR GCSE Physics A: Gateway Science (J249) — P5.1 Energy stores and transfers · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

The ball has gravitational potential energy (GPE) at the start. As it falls, GPE is converted into kinetic energy (KE). When it strikes the floor, the KE is stored as elastic potential energy (EPE) as the ball deforms. The ball then recoils, converting the EPE back into KE for the upward motion. At each impact a part of the KE is lost to heat and sound, so the bounce height decreases. Repeating this, the ball’s energy is gradually transferred to thermal energy and sound until all the original GPE has been dissipated and the ball comes to rest.

Examiner tips

  • Use the exact terms GPE, KE, EPE and state the direction of transfer. Mention the loss of energy as heat/sound at each bounce. Show the final state as rest with all energy dissipated.
  • Keep the answer concise – 4 marks can be earned with a short paragraph covering each stage.

Mark scheme (4 marks)

  1. The ball starts with gravitational potential energy (GPE) which transfers to kinetic energy (KE) as it falls
  2. When the ball hits the floor, kinetic energy is transferred to elastic potential energy as the ball deforms/is squashed
  3. Each bounce involves a waste energy transfer — kinetic energy is transferred to thermal energy (heat) and/or sound
  4. The ball comes to rest because, by conservation of energy, all the original gravitational potential energy has been transferred to thermal energy and sound — none is created or destroyed

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