A pendulum swings back and forth. Describe the energy changes that take place as the pendulum swings from its highest point on one side to its lowest point, and explain what happens to the total energy of the system.

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).

A pendulum is released from rest at its highest point and swings down to its lowest point.

Model answer (4 marks)

At the highest point the pendulum has maximum gravitational potential energy.
As it swings down, this potential energy is converted into kinetic energy.
At the lowest point the pendulum has maximum kinetic energy.
The total energy of the system remains constant – energy is conserved.

Examiner tips

  • Use the exact terms ‘maximum gravitational potential energy’ and ‘maximum kinetic energy’.
  • Show the transfer of energy from potential to kinetic as the pendulum moves.
  • Mention that the total energy is conserved because energy cannot be created or destroyed.
  • Keep the answer concise – one sentence per point.

Mark scheme (4 marks)

  1. At the highest point the pendulum has (maximum) gravitational potential energy
  2. As the pendulum swings down, gravitational potential energy is transferred to kinetic energy
  3. At the lowest point the pendulum has (maximum) kinetic energy
  4. The total energy of the system remains constant / is conserved (because energy cannot be created or destroyed)

Key terms in this question

system

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