AS Daily A Level Physics question
A trolley’s displacement from a motion sensor is plotted against time. For a 4 s interval the displacement–time graph is a straight horizontal line. Which statement must be true during that interval?
Answer
The correct answer is D.
Correct: D — It is stationary; its displacement is constant. A horizontal displacement–time line means displacement does not change, so velocity and speed are zero. A says constant non-zero speed, which would require a sloped line, not a flat one. B says motion toward the sensor, which would be a straight line sloping down (if toward is defined as negative), not horizontal. C confuses constant with zero; the line could be at any fixed displacement, not necessarily at zero. D correctly identifies that the object is at rest and its displacement remains unchanged.