A skydiver jumps from an aeroplane and falls vertically downwards. At first, the skydiver accelerates. After some time, the skydiver reaches terminal velocity. Explain why the skydiver first accelerates and then reaches terminal velocity.

Eduqas GCSE Physics — 4.2 Forces, accelerations and Newton's laws of motion · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

1. At the start the skydiver’s weight (mg) is greater than the air resistance, so the net force is downward.
2. Because the net force is unbalanced, Newton’s second law gives a downward acceleration.
3. As the speed increases, the drag force increases.
4. When the drag equals the weight the net force is zero and the skydiver reaches terminal velocity, moving at constant speed.

Examiner tips

  • Use the exact terms ‘weight’, ‘air resistance’, ‘net force’ and ‘terminal velocity’.
  • Show the logical sequence: weight > drag → acceleration → drag increases → drag = weight → zero net force → constant speed.

Common mistakes

  • Confusing drag with weight or omitting the net force step.
  • Using ‘gravity’ instead of ‘weight’ or not recognising that terminal velocity occurs when forces balance.

Mark scheme (4 marks)

  1. At the start, the weight (gravitational force) is greater than the air resistance (drag)
  2. Because there is a resultant (net) downward force, the skydiver accelerates (Newton's second law / unbalanced force causes acceleration)
  3. As speed increases, air resistance (drag) increases
  4. At terminal velocity, air resistance equals weight, so the resultant force is zero and the skydiver moves at constant velocity

Key terms in this question

terminal velocity

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