Acceleration — AQA GCSE Physics
Test yourself on Acceleration with AQA GCSE practice questions.
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Acceleration explained
This equation links the change in the square of velocity to acceleration and distance for motion in a straight line with constant acceleration.
Read the full explanation
The symbol v is final velocity in metres per second (m/s), u is initial velocity in m/s, a is acceleration in m/s² and s is distance in metres (m). The term v² − u² is the difference between the squares of the final and initial velocities, not the square of the difference. To use it, list the known quantities with units, rearrange for the unknown, substitute values and solve. For example, a car accelerating uniformly from rest (u = 0 m/s) over 50 m with a = 2 m/s² has v² = 0² + 2 × 2 × 50 = 200 m²/s², so v = √200 ≈ 14 m/s.
Your focus
- Select and apply v² − u² = 2 a s to solve problems involving uniform acceleration in a straight line.
- Rearrange the equation to find v, u, a or s and substitute values with consistent units.
- Interpret the sign and magnitude of calculated values in the context of the motion described.
Acceleration exam tips
Marking Points
- States that v is final velocity in m/s, u is initial velocity in m/s, a is acceleration in m/s² and s is distance in m.
- Recognises that the equation applies to uniform acceleration in a straight line.
- Calculates v² − u² correctly by squaring each velocity before subtracting, rather than squaring the difference between the velocities.
- Rearranges the equation correctly for the required quantity, for example v = √(u² + 2 a s) or s = (v² − u²) ÷ (2 a).
- Substitutes values with consistent units and evaluates the square root when finding v, giving the final velocity with the correct unit and a sensible magnitude.
- Interprets a negative value of v² − u² as deceleration, indicating that the final speed is less than the initial speed.
Examiner Tips
- 💡Write down u, v, a and s with their units before substituting, so it is clear which quantity is unknown.
- 💡Show the rearrangement step explicitly, especially when the unknown is v or s, to make the method clear.
- 💡Check that the final answer has the correct unit and a realistic size for the context described.
Common Mistakes
- Squaring the difference between the velocities instead of subtracting the squares; correct this by squaring u and v separately before subtracting.
- Forgetting to take the square root after finding v²; correct this by applying the square root to the value of v² to obtain v.
- Confusing the symbol 's' with speed; correct this by remembering that 's' stands for distance in this kinematic equation.