A skydiver jumps from an aircraft and falls towards the ground. Explain why the skydiver first accelerates and then reaches a terminal velocity.

Edexcel GCSE Physics (1PH0) — 9.1 Forces and their effects · Explain · 4 marks · View as Markdown

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

A skydiver jumps from an aircraft at high altitude and falls vertically downwards through the air.

Model answer (4 marks)

Initially the skydiver’s weight is greater than the air resistance, so the resultant force acts downwards and the skydiver accelerates.
As the speed increases, the air resistance increases.
The resultant force therefore decreases, so the acceleration decreases.
When the air resistance equals the weight, the resultant force is zero and the skydiver reaches terminal velocity, so there is no further acceleration.

Examiner tips

  • Use the word ‘resultant force’ to link weight and air resistance
  • Show the change in force as speed increases
  • Explain that zero resultant force gives zero acceleration
  • Keep the answer concise and use the exact terms

Common mistakes

  • Forgetting to mention the resultant force becomes zero at terminal velocity
  • Using ‘gravity’ instead of ‘weight’
  • Not linking the increase in air resistance to the decrease in acceleration

Mark scheme (4 marks)

  1. Initially, weight is greater than air resistance (resultant force acts downwards), so the skydiver accelerates.
  2. As the skydiver's speed increases, air resistance increases.
  3. The resultant force decreases as air resistance increases, so acceleration decreases.
  4. Terminal velocity is reached when air resistance equals weight, so the resultant force is zero and there is no acceleration.

Key terms in this question

terminal velocity

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