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AS Daily A Level Physics question

2025-09-30 OCR A Dynamics: forces, free-body diagrams; Newton’s laws; friction and drag (qualitative) 3.2.2(d)(i)

Which statement must be true when a skydiver has just reached terminal speed during a vertical fall?

  1. A The skydiver’s weight has decreased until it matches the drag force.
  2. B The resultant force is downward but very small because the speed is large.
  3. C The upward drag equals the weight; acceleration is zero, but forces still act. (correct)
  4. D Air resistance no longer acts because the speed has stopped changing.

Answer

The correct answer is C.

Correct: C — The upward drag equals the weight; acceleration is zero, but forces still act. A — Weight does not decrease during the fall; drag increases with speed until it balances the (essentially constant) weight. B — A downward resultant would mean the skydiver is still speeding up, which is not the case at terminal speed. C — This is the only option consistent with zero resultant force and constant speed at terminal conditions. D — Drag continues to act at constant speed; it does not switch off just because the speed stops changing.

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