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AS Daily A Level Physics question

2026-01-01 OCR A Kinematics (displacement–time) 3.1.1(c)

In a school lab, a toy robot moves in a straight line along a track. A motion sensor records its displacement from the start point against time. Over one 4 s interval, the displacement–time graph is a straight line with a steady positive slope. Which statement must be true during this interval?

  1. A Its speed increases since the displacement increases with time.
  2. B It moves with constant positive velocity along the track. (correct)
  3. C It has constant positive acceleration along the track.
  4. D It is stationary at a constant distance from the start point.

Answer

The correct answer is B.

Correct: B — It moves with constant positive velocity along the track. A Displacement getting larger does not imply increasing speed; a straight-line displacement–time graph has constant gradient so speed is constant. B A straight-line displacement–time segment with positive slope means a constant positive gradient, i.e. constant positive velocity. C Constant positive acceleration would make the displacement–time graph curve upward; a straight line implies zero acceleration. D Stationary motion would appear as a horizontal line with zero gradient, not a sloped line.

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