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AS Daily A Level Physics question

2025-12-22 OCR A Kinematics: displacement–time (M3) 3.1.1(c)

A trolley’s displacement s from a motion sensor at one end of a straight track is recorded against time t. The displacement–time graph is a straight line with a constant negative gradient. Which statement must be true?

  1. A It moves toward the sensor at constant speed. (correct)
  2. B It moves away from the sensor but slows down.
  3. C It remains at rest because the line is straight.
  4. D It accelerates because its displacement keeps changing.

Answer

The correct answer is A.

Correct: A — It moves toward the sensor at constant speed. A — A constant negative gradient on an s–t graph means constant velocity toward decreasing displacement (toward the sensor). B — A downward slope shows direction (toward the sensor), not slowing; slowing would require the line to become less steep over time. C — Stationary motion would give a horizontal line (zero gradient), not a sloped straight line. D — Acceleration would be shown by a changing gradient (a curve), but the gradient here is constant.

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