AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
If an object moves along a straight line, the distance travelled can be…
Full specification wording
The distance–time relationship: If an object moves along a straight line, the distance travelled can be represented by a distance–time graph.
A distance–time graph plots distance travelled on the vertical axis against time on the horizontal axis for motion along a straight line.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 1 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A distance–time graph plots distance travelled on the vertical axis against time on the horizontal axis for motion along a straight line. The gradient of the line gives the speed: a steeper line means a greater speed, a horizontal line means the object is stationary, and a straight line means constant speed. For example, a cyclist travelling 100 m in 20 s gives a straight line from (0 s, 0 m) to (20 s, 100 m), with gradient 100 m ÷ 20 s = 5 m/s. A curved line shows changing speed, meaning the object is accelerating or decelerating. The graph represents distance travelled, not displacement, so it does not show direction. Reading values from the axes and calculating gradients for straight lines are key skills.
What earns the marks
- Plots distance travelled on the vertical axis and time on the horizontal axis with suitable scales and labels.
- Interprets the gradient of the line as the speed of the object.
- Identifies a horizontal line as an object at rest and a straight sloping line as constant speed.
- Calculates speed from the gradient using speed = distance ÷ time with correct units.
- Recognises that a curved line represents changing speed, indicating acceleration or deceleration.
Common mistakes and how to put them right
Reading the vertical axis as speed rather than distance.
Put it right by checking the axis label before interpreting the graph.
Assuming a horizontal line means the object is moving slowly.
Put it right by stating it shows the object is stationary.
Calculating gradient as time ÷ distance.
Put it right by dividing the change in distance by the change in time.
Exam tips
- Label both axes with quantity and unit before plotting or reading points.
- Show the gradient calculation clearly, including the values substituted and the unit m/s.
- Check whether the graph is a straight line or a curve before deciding whether speed is constant or changing.
Try the lesson
The start of the The distance–time relationship: If an object moves along a straight line, the distance travelled can be represented by a distance–time graph. lesson, made from checked teaching notes for this specification point.
Have a go first
On a distance–time graph, what does a horizontal line show about an object moving along a straight line?
Listen
A distance–time graph plots distance travelled on the vertical axis against time on the horizontal axis for motion along a straight line. The gradient of the line gives the speed: a steeper line means a greater speed, a horizontal line means the object is stationary, and a straight line means constant speed. For example, a cyclist travelling 100 m in 20 s gives a straight line from (0 s, 0 m) to (20 s, 100 m), with gradient 100 m ÷ 20 s = 5 m/s. A curved line shows changing speed, meaning the object is accelerating or decelerating. The graph represents distance travelled, not displacement, so it does not show direction. Reading values from the axes and calculating gradients for straight lines are key skills. A strong answer earns marks for these points. Plots distance travelled on the vertical axis and time on the horizontal axis with suitable scales and labels. Interprets the gradient of the line as the speed of the object. Identifies a horizontal line as an object at rest and a straight sloping line as constant speed. Calculates speed from the gradient using speed = distance ÷ time with correct units. A common slip: Reading the vertical axis as speed rather than distance. Instead, checking the axis label before interpreting the graph. Exam tip: Label both axes with quantity and unit before plotting or reading points.
See it
Key words
Say what each word means before you turn the card.
distance–time graph
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gradient
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straight line
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curved line
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See every definition
- distance–time graph
- A graph that plots distance travelled on the vertical axis against time on the horizontal axis for motion along a straight line.
- gradient
- The gradient of the line gives the speed, calculated by dividing the change in distance by the change in time.
- straight line
- A straight line means constant speed, while a horizontal line means the object is stationary.
- curved line
- A curved line shows changing speed, meaning the object is accelerating or decelerating.
Label the diagram
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