A archer pulls back the string of a bow, then releases the arrow. Describe the energy changes that take place from the moment the archer begins to pull the string until the arrow is flying through the air.

AQA GCSE Physics (8463) — 4.1.1 Energy changes in a system, and the ways energy is stored before and after such changes · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

1. Elastic potential energy is stored in the bow and string as the archer pulls the string back.
2. When the string is released, the stored elastic potential energy is transferred to the arrow.
3. The arrow gains kinetic energy and moves forward.
4. Some of the energy is lost as thermal energy (and sound) due to friction and air resistance.

Examiner tips

  • Use the word "elastic potential energy" and "kinetic energy" exactly. Show the transfer of energy from bow to arrow. Mention the loss of energy to heat/sound to earn the final point.

Common mistakes

  • Confusing potential energy with kinetic energy of the bow. Forgetting to mention energy loss as heat or sound. Using vague terms like "energy" without specifying type.

Mark scheme (4 marks)

  1. Elastic potential energy is stored in the bow/string as it is stretched
  2. When the string is released, elastic potential energy is transferred to the arrow
  3. The arrow gains kinetic energy as it moves
  4. Some energy is dissipated/wasted as thermal energy (and/or sound) due to friction/air resistance

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