Uniform Acceleration (v² − u² = 2as)

✏️ Paper first! Work out every question on paper before you tap Show solution. Write down every step – the equation, the numbers with units, the rearranging and the answer with its unit. In the exam, if your final answer is wrong you can still get marks for correct working, but only if the examiner can see it.

Course: Combined Science + Separate Physics  |  Tier: Foundation + Higher  |  Equation sheet: given in the exam

The equation

(final velocity)² − (initial velocity)² = 2 × acceleration × distance    v² − u² = 2 a s

QuantitySymbolUnit
final velocityvmetres per second (m/s)
initial velocityumetres per second (m/s)
accelerationametres per second squared (m/s²)
distancesmetres (m)

Rearranged: s = (v² − u²) ÷ 2a  |  a = (v² − u²) ÷ 2s  |  v = √(u² + 2as)  |  “From rest” means u = 0

Use FIFA for every answer

  • F – Formula: write the equation as it appears on the sheet.
  • I – Insert: put in the numbers (convert to standard units first).
  • F – Fix: rearrange to make the unknown the subject.
  • A – Answer: calculate and always give the unit.

Foundation: aim for Q1–8.   Higher: aim for Q4–10. Every question needs rearranging.


Questions

Q1 (F) A cyclist accelerates from rest to 6 m/s at 1.5 m/s². How far does she travel?

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F: v² − u² = 2 a s
I: 6² − 0² = 2 × 1.5 × s, so 36 = 3 × s
F: s = 36 ÷ 3
A: 12 m

Q2 (F) A sprinter starts from rest and reaches 8 m/s after 16 m. Calculate her acceleration.

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F: v² − u² = 2 a s
I: 8² − 0² = 2 × a × 16, so 64 = 32 × a
F: a = 64 ÷ 32
A: 2 m/s²

Q3 (F) A car starts from rest and accelerates at 4 m/s² over 50 m. Calculate its final speed.

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F: v² − u² = 2 a s
I: v² − 0² = 2 × 4 × 50
F: v² = 400, so v = √400
A: 20 m/s

Q4 (F) A car speeds up from 10 m/s to 20 m/s over a 75 m slip road. Calculate its acceleration.

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F: v² − u² = 2 a s
I: 20² − 10² = 2 × a × 75, so 300 = 150 × a
F: a = 300 ÷ 150
A: 2 m/s²

Q5 (F) A car travelling at 72 km/h brakes to a stop with a deceleration of 8 m/s². Calculate its braking distance.

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Convert first: 72 km/h = 72 000 ÷ 3600 = 20 m/s; deceleration means a = −8 m/s²
F: v² − u² = 2 a s
I: 0² − 20² = 2 × −8 × s, so −400 = −16 × s
F: s = −400 ÷ −16
A: 25 m

Q6 (F/H) A plane starts from rest and reaches its take-off speed of 80 m/s over 1600 m of runway. Calculate its acceleration.

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F: v² − u² = 2 a s
I: 80² − 0² = 2 × a × 1600, so 6400 = 3200 × a
F: a = 6400 ÷ 3200
A: 2 m/s²

Q7 (F/H) A car brakes with a deceleration of 6.0 m/s² and stops in 48 m. How fast was it going before braking?

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F: v² − u² = 2 a s
I: 0² − u² = 2 × −6.0 × 48, so −u² = −576
F: u² = 576, so u = √576
A: 24 m/s

Q8 (F/H) An electron starts from rest and accelerates at 4.5 × 1014 m/s² over a distance of 0.010 m. Calculate its final speed.

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F: v² − u² = 2 a s
I: v² − 0² = 2 × 4.5 × 1014 × 0.010
F: v² = 9.0 × 1012, so v = √(9.0 × 1012)
A: 3.0 × 106 m/s

Q9 (H) A 1200 kg car travelling at 30 m/s brakes with a braking force of 7200 N. Calculate its braking distance.

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Step 1 – deceleration: a = F ÷ m = 7200 ÷ 1200 = 6 m/s², so a = −6 m/s²
Step 2 – distance
F: v² − u² = 2 a s
I: 0² − 30² = 2 × −6 × s, so −900 = −12 × s
F: s = −900 ÷ −12
A: 75 m

Q10 (H) A ball is thrown straight up at 15 m/s. Calculate the maximum height it reaches, to 2 significant figures. (Acceleration due to gravity = 9.8 m/s²; ignore air resistance.)

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Think: at the top, v = 0; gravity slows it, so a = −9.8 m/s²
F: v² − u² = 2 a s
I: 0² − 15² = 2 × −9.8 × s, so −225 = −19.6 × s
F: s = −225 ÷ −19.6 = 11.47… m
A: 11 m (2 s.f.)