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AS Daily A Level Physics question

2026-03-16 OCR A Mechanics: suvat problems OCR Physics A (H156) Module 3: Forces and motion — 3.1 Motion: equations of motion (suvat) OCR Physics A (H156) Module 3: Forces and motion — 3.1 Motion: velocity–time and displacement–time reasoning

In a lab, two low-friction trolleys both start from rest and move in straight lines with constant (but not necessarily equal) accelerations. Motion sensors show trolley A travels 1.6 m in 1.0 s, while trolley B travels the same 1.6 m in 2.0 s. At the end of these times, what is the ratio v_B / v_A of B’s speed to A’s speed?

  1. A 1.0
  2. B 0.5 (correct)
  3. C 2.0
  4. D 0.25

Answer

The correct answer is B.

Correct: B — 0.5. A assumes equal final speeds because the distances are the same, but for motion from rest over a fixed distance, taking longer means a smaller final speed. B is correct because for motion from rest over distance s, v = 2s/t, so v_B/v_A = (2s/t_B)/(2s/t_A) = t_A/t_B = 1/2. C reverses the ratio, as if a longer time produced a larger final speed. D incorrectly applies a squared time effect; the final speed scales with 1/t, not 1/t^2.

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