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

Eduqas GCSE Physics — 3.1 Forces and their interactions · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

At the start the weight (mg) is greater than the upward air resistance, so the net force is downward and the skydiver accelerates.
As the speed increases, the drag force increases.
When the drag equals the weight the net force becomes zero.
At this point the skydiver moves at a constant terminal velocity.

Examiner tips

  • Use the terms weight, drag, net force and terminal velocity. Show the sequence: weight > drag → acceleration → drag ↑ → weight = drag → no acceleration.
  • Include the cause of drag increasing with speed (higher velocity → more air molecules hit the body).

Common mistakes

  • Confusing drag with weight or omitting the net force step. Forgetting to state that terminal velocity is reached when drag equals weight.

Mark scheme (4 marks)

  1. At the start, the weight (gravitational force) acting downwards is greater than the air resistance (drag) acting upwards
  2. A resultant (net) downward force causes the skydiver to accelerate downwards
  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 a constant velocity

Key terms in this question

terminal velocity

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