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AS Daily A Level Physics question

2026-05-16 OCR A Mechanics & Materials (M3) OCR A Physics A (H156) Module 3.2 Forces in action — drag and terminal speed OCR A Physics A (H156) Module 3.5 Newton’s laws of motion (qualitative)

A skydiver is falling steadily at terminal speed in a spread‑eagle position. They quickly tuck into a narrower shape, keeping the same mass and altitude. Immediately after tucking, which statement about the net force, acceleration, and speed is most accurate?

  1. A The net force becomes downward, so acceleration is downward and the speed increases toward a higher terminal value. (correct)
  2. B The net force becomes upward, so acceleration is upward and the speed decreases toward a lower terminal value.
  3. C The forces remain balanced, so acceleration is zero and the speed stays the same.
  4. D The net force is downward but the acceleration is upward, so the speed decreases because the drag is reduced.

Answer

The correct answer is A.

Correct: A — The net force becomes downward, so acceleration is downward and the speed increases toward a higher terminal value. A is correct because reducing cross‑sectional area suddenly reduces drag at the same speed, making weight exceed drag so the skydiver accelerates downward toward a new, higher terminal speed. B is wrong because tucking decreases drag, so the net force cannot be upward and the terminal speed does not become lower. C is wrong because changing shape instantly upsets the previous balance of forces; they no longer cancel at that moment. D is wrong because acceleration is in the direction of the net force; it cannot be upward while the net force is downward.

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