A child pushes a toy car along a flat surface and releases it. The car travels a short distance and then comes to a stop. Explain the energy transfers that take place from when the child pushes the car 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).

A toy car is pushed along a flat, rough surface and released. It travels a short distance before stopping completely.

Model answer (4 marks)

The child’s hand does work on the car, giving it kinetic energy. As the car moves, friction between the wheels and the rough surface acts, converting that kinetic energy into thermal energy in the car and the surface. The heat is lost to the surroundings, so the energy is dissipated but the total energy is conserved.

Examiner tips

  • Use the word ‘work’ to show the child’s force transfers energy.
  • Mention friction as the force that changes kinetic to thermal energy.
  • Explain that the energy is not destroyed, only moved to heat.
  • Keep the answer concise and use correct terminology.

Mark scheme (4 marks)

  1. Work is done by the child's force on the car, transferring energy to the car's kinetic energy store
  2. As the car moves, friction acts between the wheels/car and the surface
  3. Kinetic energy is transferred to thermal (heat) energy stores of the car/surface
  4. This is a waste energy transfer / the total energy is conserved (not destroyed) but dissipated to the surroundings

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