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
| Quantity | Symbol | Unit |
|---|---|---|
| final velocity | v | metres per second (m/s) |
| initial velocity | u | metres per second (m/s) |
| acceleration | a | metres per second squared (m/s²) |
| distance | s | metres (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?
Show solution
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.
Show solution
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.
Show solution
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.
Show solution
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.
Show solution
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.
Show solution
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?
Show solution
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.
Show solution
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.
Show solution
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.)
Show solution
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.)