Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Analyse distance/time graphs including determination of speed from the…
Full specification wording
Topic 2 – Motion and forces: 2.7 Analyse distance/time graphs including determination of speed from the gradient
A distance/time graph plots distance travelled on the vertical axis against time on the horizontal axis.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 7 of 32
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. The gradient of the line gives the speed: speed = change in distance ÷ change in time. A steeper line means a higher speed, a horizontal line means the object is stationary, and a straight line means constant speed. To find speed from a gradient, pick two points on the line, read the change in distance and the change in time between them, then divide. For example, if distance rises from 0 m to 30 m while time goes from 0 s to 6 s, the gradient is 30 m ÷ 6 s = 5 m/s. A curved line shows changing speed, and the gradient at a point gives the instantaneous speed there.
What earns the marks
- Reads the vertical axis as distance and the horizontal axis as time before interpreting the line.
- Calculates speed by dividing the change in distance by the change in time between two points on the line.
- Identifies a steeper gradient as representing a greater speed.
- States that a horizontal section of the graph shows the object is stationary.
- Recognises that a straight line indicates constant speed and a curve indicates changing speed.
Common mistakes and how to put them right
Divides time by distance instead of distance by time.
Put it right: Divide the change in distance by the change in time.
Treats a horizontal line as fast motion.
Put it right: Recognise that a horizontal line means zero speed and the object is stationary.
Reads the gradient from a single point rather than between two points.
Put it right: Use the change in distance and change in time between two chosen points.
Assumes a curved line shows constant speed.
Put it right: Recognise that a curve shows changing speed.
Exam tips
- Label the two points you use on the line and show the change in distance and change in time before dividing.
- Check the units on each axis and give the final speed in m/s.
- Use the phrase 'gradient equals speed' to justify your reasoning in a written answer.
Try the lesson
The start of the Topic 2 – Motion and forces: 2.7 Analyse distance/time graphs including determination of speed from the gradient lesson, made from checked teaching notes for this specification point.
Have a go first
On a distance/time graph, a straight line rises from 0 m at 0 s to 20 m at 4 s. What is the speed shown by the gradient of this line?
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