A battery-powered toy car is switched on and accelerates across a smooth floor. It then hits a wall and comes to a sudden stop. Explain the energy transfers that occur from the moment the toy car is switched on until it comes to rest against the wall.

Edexcel GCSE Physics (1PH0) — 3.1 Conservation of energy · 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 battery contains chemical energy, which is converted into kinetic energy of the toy car when it is switched on.
When the car collides with the wall its kinetic energy is transferred to sound and to heat (thermal energy) in the car, the wall and the surrounding air.
The total energy of the system is conserved – energy is neither created nor destroyed, only transferred between forms.
The sound and heat produced are waste energy transfers; they are dissipated to the surroundings and are not useful for the car’s motion.

Examiner tips

  • Use the word "converted" or "transferred" to link energy forms. Mention the wall and surroundings as the recipients of the waste energy. Show the conservation statement clearly. Keep the answer concise – 4 points only.

Common mistakes

  • Forgetting to mention the battery’s chemical energy as the source. Describing the collision as a loss of energy rather than a transfer to sound/heat. Including unnecessary detail such as the car’s internal friction.

Mark scheme (4 marks)

  1. Chemical energy stored in the battery is transferred to kinetic energy (of the moving car)
  2. When the car hits the wall, its kinetic energy is transferred to sound (and/or heat / thermal energy)
  3. The total energy of the system is conserved / energy is never created or destroyed, only transferred
  4. The sound and heat produced are waste energy transfers / the energy is dissipated to the surroundings

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