AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Acceleration: a = Δv / t
Acceleration measures how quickly velocity changes.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 11 of 23
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Acceleration measures how quickly velocity changes. The equation a = Δv / t links acceleration a (m/s²), to the change in velocity Δv (m/s), and the time t taken (s). Δv is found by subtracting the initial velocity from the final velocity, so Δv = v − u. For example, a cyclist speeds up from 4 m/s to 10 m/s in 3 s: a = (10 - 4) / 3 = 2 m/s². Negative acceleration indicates a velocity change in the negative direction, meaning speeding up if velocity is negative, or slowing down if positive. Always convert units before substituting, and rearrange the equation when the question asks for Δv or t rather than a. Ensure time is in seconds and velocity in m/s to yield acceleration in m/s².
What earns the marks
- State the equation as a = Δv ÷ t and identify each symbol with its unit: a in m/s², Δv in m/s and t in s.
- Calculate the change in velocity (Δv) correctly by subtracting the initial velocity from the final velocity.
- Rearrange the equation to Δv = a × t or t = Δv ÷ a when the question supplies acceleration and asks for velocity change or time.
- Interpret negative acceleration as a negative velocity change, meaning speeding up if velocity is negative, or slowing down if positive.
Common mistakes and how to put them right
Assuming negative acceleration always means deceleration.
Put it right: Recognise it means speeding up if the object is moving in the negative direction.
Forgetting to convert time units like minutes into seconds.
Put it right: Multiply minutes by 60 before calculating.
Adding the initial and final velocities instead of subtracting to find Δv.
Put it right: Subtract the initial velocity from the final velocity.
Exam tips
- Check the question wording for direction; negative acceleration means deceleration only if initial velocity is positive.
- Write out the formula and substitute the numbers before rearranging to secure method marks.
Try the lesson
The start of the Acceleration: a = Δv / t lesson, made from checked teaching notes for this specification point.
Have a go first
A cyclist's velocity changes by 15 m/s in 3 s. Using the equation a = Δv / t, what is the cyclist's acceleration?
Listen
Acceleration measures how quickly velocity changes. The equation a = Δv / t links acceleration a (m/s²), to the change in velocity Δv (m/s), and the time t taken (s). Δv is found by subtracting the initial velocity from the final velocity, so Δv = v − u. For example, a cyclist speeds up from 4 m/s to 10 m/s in 3 s: a = (10 - 4) / 3 = 2 m/s². Negative acceleration indicates a velocity change in the negative direction, meaning speeding up if velocity is negative, or slowing down if positive. Always convert units before substituting, and rearrange the equation when the question asks for Δv or t rather than a. Ensure time is in seconds and velocity in m/s to yield acceleration in m/s². A strong answer earns marks for these points. State the equation as a = Δv ÷ t and identify each symbol with its unit: a in m/s², Δv in m/s and t in s. Calculate the change in velocity (Δv) correctly by subtracting the initial velocity from the final velocity. Rearrange the equation to Δv = a × t or t = Δv ÷ a when the question supplies acceleration and asks for velocity change or time. Interpret negative acceleration as a negative velocity change, meaning speeding up if velocity is negative, or slowing down if positive. A common slip: Assuming negative acceleration always means deceleration. Instead, recognise it means speeding up if the object is moving in the negative direction. Exam tip: Check the question wording for direction; negative acceleration means deceleration only if initial velocity is positive.
See it
Key words
Say what each word means before you turn the card.
Acceleration
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Change in velocity (Δv)
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Negative acceleration
Try answering aloud or in your head before turning the card.
See every definition
- Acceleration
- Measures how quickly velocity changes, linked by the equation a = Δv / t to the change in velocity and the time taken.
- Change in velocity (Δv)
- Found by subtracting the initial velocity from the final velocity, so Δv = v − u.
- Negative acceleration
- Indicates a velocity change in the negative direction, meaning speeding up if velocity is negative, or slowing down if positive.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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