AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Acceleration: acceleration, a, in metres per second squared, m/s²
Acceleration, symbol a, is the rate of change of velocity, measured in metres per second squared (m/s²).
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 6 of 23
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Acceleration, symbol a, is the rate of change of velocity, measured in metres per second squared (m/s²). It is a vector: speeding up, slowing down or changing direction all involve acceleration. The defining relationship is a = (v − u) ÷ t, where v is final velocity, u is initial velocity and t is the time taken. For example, a cyclist increasing from 4 m/s to 10 m/s in 3 s has a = (10 − 4) ÷ 3 = 2 m/s². A value of 2 m/s² means the velocity changes by 2 m/s every second. Negative acceleration, sometimes called deceleration, means the velocity change opposes the chosen positive direction. On a velocity–time graph, acceleration is the gradient, so a straight rising line shows constant positive acceleration and a horizontal line shows zero acceleration.
What earns the marks
- Defines acceleration as the rate of change of velocity and gives the unit m/s².
- Uses a = (v − u) ÷ t, subtracting the initial velocity from the final velocity before dividing by time.
- Interprets a numerical value such as 2 m/s² as a velocity change of 2 m/s each second.
- Explains that negative acceleration means the velocity change is opposite to the chosen positive direction.
- Reads acceleration from the gradient of a velocity–time graph, including zero gradient for constant velocity.
Common mistakes and how to put them right
Dividing the final velocity by time instead of the change in velocity.
Put it right by calculating v − u first.
Writing the unit as m/s rather than m/s².
Put it right by remembering that velocity changes by so many m/s each second.
Treating negative acceleration as always meaning the object is stationary.
Put it right by explaining that it is slowing down or moving in the negative direction.
Exam tips
- Write the equation a = (v − u) ÷ t, then substitute values one at a time to avoid sign errors.
- Check the unit of every answer against the quantity: acceleration must be in m/s².
- For graph questions, choose two points far apart on the line and divide the velocity change by the time interval.
Try the lesson
The start of the Acceleration: acceleration, a, in metres per second squared, m/s² lesson, made from checked teaching notes for this specification point.
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What is the standard unit for acceleration?
Listen
Acceleration, symbol a, is the rate of change of velocity, measured in metres per second squared (m/s²). It is a vector: speeding up, slowing down or changing direction all involve acceleration. The defining relationship is a = (v − u) ÷ t, where v is final velocity, u is initial velocity and t is the time taken. For example, a cyclist increasing from 4 m/s to 10 m/s in 3 s has a = (10 − 4) ÷ 3 = 2 m/s². A value of 2 m/s² means the velocity changes by 2 m/s every second. Negative acceleration, sometimes called deceleration, means the velocity change opposes the chosen positive direction. On a velocity–time graph, acceleration is the gradient, so a straight rising line shows constant positive acceleration and a horizontal line shows zero acceleration. A strong answer earns marks for these points. Defines acceleration as the rate of change of velocity and gives the unit m/s². Uses a = (v − u) ÷ t, subtracting the initial velocity from the final velocity before dividing by time. Interprets a numerical value such as 2 m/s² as a velocity change of 2 m/s each second. Explains that negative acceleration means the velocity change is opposite to the chosen positive direction. A common slip: Dividing the final velocity by time instead of the change in velocity. Instead, calculating v − u first. Exam tip: Write the equation a = (v − u) ÷ t, then substitute values one at a time to avoid sign errors.
See it
Key words
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Acceleration
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Vector nature of acceleration
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Velocity–time graph gradients
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Negative acceleration
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See every definition
- Acceleration
- The rate of change of velocity, symbol a, measured in metres per second squared (m/s²).
- Vector nature of acceleration
- Speeding up, slowing down or changing direction all involve acceleration, so it is a vector.
- Velocity–time graph gradients
- Acceleration is the gradient, so a straight rising line shows constant positive acceleration and a horizontal line shows zero acceleration.
- Negative acceleration
- Sometimes called deceleration, it means the velocity change opposes the chosen positive direction.
Label the diagram
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1Box 1
2Box 2
3Box 3
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