A skydiver jumps from an aircraft and falls through the air. Describe how the skydiver's acceleration changes from the moment they jump until they reach terminal velocity, and explain why these changes occur.

Cambridge International IGCSE Physics (0625) — 1.2 Motion · Describe and explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Initially the skydiver accelerates at g (≈9.8 m s⁻²) because the only force is gravity. As the speed increases, air resistance grows, reducing the net downward force. Consequently the acceleration decreases. When the upward drag equals the downward weight the net force is zero, so the acceleration becomes zero and the skydiver reaches terminal velocity.

Examiner tips

  • Use the word ‘initially’ to show the first stage, then ‘as speed increases’ for the middle stage, and finish with ‘when drag equals weight’ for the final stage.
  • Mention the forces (weight, drag) and the concept of net force to justify the change in acceleration.

Common mistakes

  • Saying the acceleration stays at g until terminal velocity; ignores the drag effect.
  • Confusing terminal velocity with the speed at which the skydiver starts falling; terminal velocity is the constant speed after acceleration stops.

Mark scheme (4 marks)

  1. Initially, acceleration is at its maximum (equal to g / approximately 9.8 m/s²) because the only force acting is the skydiver's weight / there is no air resistance at the start
  2. As speed increases, air resistance increases
  3. The resultant (downward) force decreases, so acceleration decreases
  4. When air resistance equals weight, the resultant force is zero, so acceleration is zero and terminal velocity is reached

Key terms in this question

terminal velocity · acceleration

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