Back to Daily Question archive

AS Daily A Level Physics question

2025-09-27 OCR A Physical quantities & SI, Scalars vs vectors, Kinematics: displacement–time 3.1.1(a) 3.1.1(c)

A trolley moves along a straight track. Its displacement s from the start is recorded versus time t. The displacement–time graph is piecewise straight: from t = 0 to 8 s, s increases uniformly from 0 m to +6 m; from 8 s to 12 s, s is constant at +6 m; from 12 s to 24 s, s decreases uniformly back to 0 m. Which statement must be true?

  1. A A The average velocity from 0 to 24 s is +0.50 m s^-1 since 12 m is covered in 24 s.
  2. B B The average speed from 0 to 24 s is 0.50 m s^-1, and the average velocity over the same interval is 0 m s^-1. (correct)
  3. C C The instantaneous velocity is zero between 0 and 8 s because the motion starts at s = 0 m.
  4. D D The speed between 12 and 24 s is 1.5 times the speed between 0 and 8 s because that time interval is longer.

Answer

The correct answer is B.

Correct: B — B The average speed from 0 to 24 s is 0.50 m s^-1, and the average velocity over the same interval is 0 m s^-1. Total distance is 6 m out and 6 m back = 12 m, so average speed = 12/24 = 0.50 m s^-1, while total displacement over 0–24 s is 0, so average velocity is 0. A Average velocity uses net displacement (0 m) over time, not total distance, so it is not +0.50 m s^-1. B This correctly distinguishes scalar speed from vector velocity and uses the correct distances and times. C From 0–8 s the graph has a positive slope, so velocity is constant and non-zero; starting at s = 0 m does not imply zero velocity. D The same 6 m is covered over a longer time (12 s vs 8 s), so the return speed is smaller (0.50 vs 0.75 m s^-1), not 1.5 times larger.

Try today's guest Daily MCQ A Level Physics MCQ practice Problem-solving previews