Reading Distance-Time Graphs
Read and plot distance-time graphs for moving objects; interpret the gradient (steepness) of a line as speed; identify stationary periods (horizontal sections), constant speed (straight diagonal lines), and relative speeds by comparing gradients; calculate average speed from the gradient of a straight-line segment using speed = distance ÷ time
What a learner can do afterwards
- Read a distance-time graph and describe what is happening at each stage: moving, stopped, returning
- Calculate speed from the gradient of a straight section of a distance-time graph
- Sketch a distance-time graph from a written description of a journey with stops and speed changes
1 · Read
A distance-time graph shows how far something has traveled as time passes. Time runs along the bottom. Distance goes up the side. Reading the line from left to right tells you the story of a journey.
The steepness of the line is called the gradient, and the gradient tells you the speed. A steep line means a lot of distance covered in a short time, so the object was moving fast. A gentle line means it was moving slowly.
Zara's line rises from 0 to 100 meters over 20 seconds. Her speed is distance divided by time: 100 divided by 20 equals 5 meters per second. If the next part of the line is flatter than that, she has slowed down.
When comparing two lines, the steeper one always shows the faster speed, even if it starts lower down on the graph.
A steeper line means a faster speed, a flat line means the object has stopped, and speed always comes from distance divided by time.
More to read
3 Ways to Calculate Distance
A distance-time graph shows how far an object has traveled over time. The horizontal axis is time. The vertical axis is distance. A flat horizontal line means the object is stopped. A straight diagonal line means constant speed. The steeper the line, the faster the speed. A curved line means changing speed. If the curve gets steeper, the object is speeding up. If it gets flatter, the object is slowing down.
Key ideas: Interpret line graphs
You can find speed from a distance-time graph. On a straight section, speed equals the gradient (slope). Pick two points on the line. Divide the change in distance by the change in time. That is the average speed for that section. Speed = distance / time. The units are distance units per time units, like meters per second or kilometers per hour.
Interpreting and comparing proportional relationships
A journey with stops and speed changes makes a graph with different sections. Flat sections are stops. Diagonal sections are constant speed. Curved sections are acceleration or deceleration. A line that goes back toward the start means the object is returning. You can sketch a graph from a story: start flat, go diagonal for steady travel, go flat for a stop, curve up for speeding up, diagonal for steady speed, curve down for slowing down, flat for final stop.
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2 · Watch
به انگلیسیTake it off screen
Where it sits
Learn first
Optional connections
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
12 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.