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AS Daily A Level Physics question

2026-02-01 OCR A Dynamics — terminal velocity and drag OCR AS Physics A (H156) Module 3.1.2 Forces in action — drag and terminal velocity; Newton’s laws

Two skydivers of the same size, shape and body position fall with parachutes closed. In this regime, air drag is proportional to the square of speed. The second skydiver carries 25% extra mass (same area and drag coefficient). Compared with the first, what happens to the second skydiver’s terminal speed, and why?

  1. A No change; terminal speed depends only on shape and area, not mass.
  2. B Increases by 25%, because balancing a 25% larger weight needs a 25% higher speed.
  3. C Decreases by about 12%, because the greater inertia makes air resistance less effective.
  4. D Increases by about 12%, because balancing 1.25 times the weight needs speed about √1.25 ≈ 1.12 times larger. (correct)

Answer

The correct answer is D.

Correct: D — Increases by about 12%, because balancing 1.25 times the weight needs speed about √1.25 ≈ 1.12 times larger. A ignores that terminal velocity is reached when weight equals drag; with the same area/shape, a larger weight must be balanced by a larger drag, so mass matters. B assumes drag increases linearly with speed; with drag proportional to speed squared, terminal speed scales with the square root of mass, not directly with mass. C has the wrong sign: a greater weight requires a higher balancing drag, which is achieved by a higher, not lower, terminal speed; inertia doesn’t change the drag law. D uses the correct proportional reasoning: mg balanced by k v^2 gives v ∝ √m, so a 1.25× mass gives about a 12% higher terminal speed.

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