Speed & Distance-Time Graphs
Calculate average speed using the equation speed = distance ÷ time, represent journeys on distance-time graphs, and interpret gradient as speed and flat sections as stationary periods
What a learner can do afterwards
- Uses speed = distance ÷ time to calculate average speed with correct units (m/s, km/h)
- Draws a distance-time graph for a given journey with correct axes and labels
- Reads a distance-time graph to determine speed, stopping points, and direction of travel
- Identifies which section of a distance-time graph represents the fastest speed
1 · Read
Speed tells you how fast something is moving. You work it out with a simple rule: speed = distance ÷ time. If a cyclist travels 20 kilometres in 4 hours, their average speed is 20 ÷ 4 = 5 kilometres per hour (km/h).
You already know how to read a distance-time graph. Now look closer at the slope, or gradient, of the line. A steep line means the distance is changing fast, so the speed is high. A gentle line means a slower speed. A flat, level line means the distance is not changing at all, so the object is stationary.
Mia's distance-time graph shows her walking 6 km in the first 2 hours, then a flat line for 1 hour while she eats lunch, then 4 km more in the next 2 hours. Her fastest section is the first 2 hours, because the line is steepest there. Her overall average speed uses the whole trip: total distance ÷ total time = 10 km ÷ 5 hours = 2 km/h.
Flat does not mean slow, it means stopped. Compare the steepness of different sections to find out which part of a journey was fastest.
Gradient shows speed: steeper means faster, flat means stopped, and average speed always comes from total distance ÷ total time.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
17 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.