Acceleration and Equations of Motion — AQA GCSE Physics
Acceleration describes how quickly velocity changes. It can be calculated and shown on graphs.
Acceleration
Acceleration is the change in velocity per second, measured in m/s²:
$$a = \frac{\Delta v}{t}$$ (change in velocity ÷ time taken)
A negative acceleration means the object is slowing down (deceleration).
The uniform acceleration equation
For constant (uniform) acceleration: $$v^2 - u^2 = 2as$$
- v = final velocity (m/s)
- u = initial velocity (m/s)
- a = acceleration (m/s²)
- s = distance (m)
Free fall
Near the Earth's surface, objects in free fall accelerate at about 9.8 m/s² due to gravity (often taken as 9.8 or 10 m/s²).
Typical values
You should know rough everyday values, e.g. a car can accelerate at around 2 m/s²; the acceleration of free fall is about 9.8 m/s².
Worked example
A car speeds up from 5 m/s to 25 m/s in 4 s.
- a = (25 − 5) ÷ 4 = 20 ÷ 4 = 5 m/s².
Exam tips
- Acceleration = change in velocity ÷ time (m/s²).
- Learn v² − u² = 2as for uniform acceleration.
- Free-fall acceleration ≈ 9.8 m/s².
- A negative acceleration means deceleration.