1Plotting a journey
A distance–time graph shows how far something is from its starting point at each moment. Time goes along the bottom and distance up the side.
distance–time graph
Lesson 18.3 notes
Distance–time graphs
Drawing and reading distance–time graphs, speed from the gradient, and changing speed.
2Stopped
When something stops, its distance from the start stays the same, so its line is flat (horizontal). It is stationary.
stationary
3Steady speed
At a steady speed the same distance is added every second, so the line is straight and slopes upwards.
steady speed
4Steeper is faster
A faster object covers more distance in the same time, so its line is steeper. A slower one has a gentler slope.
steeper
5Speed from the gradient
The gradient (steepness) of the line is the speed: change in distance ÷ change in time. Rising 20 m in 10 s means 2 m/s.
gradient
6Coming back
A line sloping down means the distance from the start is getting smaller: the object is coming back. At zero, it is back where it started.
7Changing speed
A curved line means the speed is changing. A line getting steeper means speeding up; one getting flatter means slowing down.
speeding upslowing down
Explore: Graph builder
Build a journey 10 seconds at a time. Watch the walker move and the distance–time graph grow.
Common mistake: A flat line doesn't mean a steady speed
On a distance–time graph, a horizontal line means the distance isn't changing, so the object has stopped. A steady speed is a straight line that slopes.
Remember
- Flat line: stopped. Straight sloping line: steady speed. Steeper: faster.
- A line sloping down means coming back towards the start. A curving line means the speed is changing.
- speed = gradient = change in distance ÷ change in time.
Going further at GCSE
GCSE: Distance–time graphs → GCSE: Distance, speed and velocity →