Question 1
The displacement–time graph of an object moving along a straight path is shown below.
| t (s) | 0 | 6 |
|---|---|---|
| s (m) | 0 | 24 |
What is the object's velocity?
The right answer is the one marked above.
4 m s-1. The gradient of a displacement–time graph is the velocity. Take two points on the line — (0, 0) and (6, 24) — and work out the gradient:
gradient = (24 − 0) m ÷ (6 − 0) s = 24 ÷ 6 = 4 m s-1
24 m s-1 is the total displacement, not the velocity — it still has to be divided by the time. 0.25 comes from dividing the other way round, time by displacement.
Since the graph is a straight line, its gradient is the same everywhere — so we can say the velocity is uniform without any calculation at all.