Graphs of Motion
Distance–time graph
A graph showing distance against time; its gradient gives the speed.
| English | Distance–time graph |
|---|---|
| Bahasa Melayu | Graf jarak–masa |
| 中文 | 距离-时间图 |
How it is used
A car travels along a straight road, drawn as a line from (0 s, 0 m) to (20 s, 300 m). The gradient is 300 ÷ 20 = 15, so the car moves at a steady 15 m/s.
Where it shows up in SPM
In the Graphs of Motion chapter (Form 5). Common in Paper 2 as a multi-part question: read distance at a given time, find speed from a gradient, describe a stationary period (a horizontal segment), or compute average speed over the whole journey.
Don't confuse it with
Open the chapter: Graphs of Motion →
Frequently asked questions
What does a horizontal line on a distance–time graph mean?
A horizontal line means the distance is not changing while time passes, so the object is stationary. Its gradient is zero, which gives a speed of 0 m/s.
Segments before and after it show the object moving again.
How do I find speed from a distance–time graph?
Take two clear points on the line and work out gradient = change in distance ÷ change in time. For a line from (0, 0) to (4 s, 100 m), speed = 100 ÷ 4 = 25 m/s.
A steeper line means a faster speed.
Is average speed the same as the gradient of each segment?
No. Each segment's gradient gives the speed during that part only.
Average speed uses the whole journey: total distance ÷ total time, including any resting periods. The two match only when the graph is a single straight line.