Graphs of Motion
Acceleration
The rate of change of speed, read as the gradient of a speed–time graph.
| English | Acceleration |
|---|---|
| Bahasa Melayu | Pecutan |
| 中文 | 加速度 |
How it is used
A motorcycle's speed rises from 10 m/s to 30 m/s in 5 s. Acceleration = (30 − 10) ÷ 5 = 20 ÷ 5 = 4 m/s².
This is the gradient of that part of the speed–time graph.
Where it shows up in SPM
In Graphs of Motion (Form 5), almost always via a speed–time graph. Paper 2 questions ask you to compute acceleration from a gradient, spot when acceleration is zero (a flat line), or recognise deceleration as a negative value.
Don't confuse it with
Open the chapter: Graphs of Motion →
Frequently asked questions
What are the units of acceleration and why?
The units are m/s² (metres per second squared). Acceleration is a change in speed (m/s) divided by time (s), so the units become (m/s) ÷ s = m/s².
Always include the squared second in your answer.
Can acceleration be zero even when the object is moving?
Yes. If the speed stays constant, say a steady 30 m/s shown as a flat horizontal line on the speed–time graph, there is no change in speed, so the gradient and the acceleration are both zero even though the object keeps moving.
What does a negative acceleration mean?
It means the object is slowing down, called deceleration. For a fall from 25 m/s to 5 m/s in 4 s, acceleration = (5 − 25) ÷ 4 = −5 m/s².
The minus sign shows the speed is decreasing, not that the object moves backward.