AS Daily A Level Physics question
A delivery robot moves along a straight corridor. Its displacement–time graph is a straight line from 0 m at t = 0 s to +5 m at t = 10 s, then a straight line to −1 m at t = 20 s (it passes the origin and ends 1 m on the other side). Which value is the robot’s average speed over 0–20 s?
Answer
The correct answer is D.
Correct: D — 0.55 m/s. A uses net displacement over time (|−1 m|/20 s), which gives the magnitude of average velocity, not average speed. B takes only the first 10 s (5 m in 10 s) and ignores the return leg. C adds 5 m and 1 m, misreading the second segment; the robot actually travels 6 m from +5 m to −1 m. D uses total distance (5 m + 6 m = 11 m) over total time (20 s), so 11/20 = 0.55 m/s.