10 GCSE Physics questions about the electric car that get harder as you go, from Foundation to Higher, each with a full worked answer. An electric car stores energy in a large battery in its floor. Electric motors turn the wheels, and when the car slows down the motors can work in reverse to put some of the energy back into the battery – this is called regenerative braking.
Course: Combined Science + Separate Physics | Tier: Foundation + Higher | Topics: Forces · Energy · Electricity
📌 KEY DEFINITIONS – learn them word for word
Kinetic energy store: the energy an object has because it is moving.
Thinking distance: the distance the car travels during the driver’s reaction time.
Braking distance: the distance the car travels under the braking force.
Stopping distance: thinking distance + braking distance.
Equations you’ll use
| Quantity | Symbol | Unit |
|---|---|---|
| kinetic energy | Eₖ | joules (J) |
| mass | m | kilograms (kg) |
| speed | v | metres per second (m/s) |
| power | P | watts (W) or kilowatts (kW) |
| potential difference | V | volts (V) |
| current | I | amps (A) |
| force | F | newtons (N) |
| acceleration | a | m/s² |
| distance | s | metres (m) |
Use FIFA for every calculation
- 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.
Questions
Q1 (F) A 1600 kg electric car travels at 15 m/s. Calculate its kinetic energy.
Show solution
F: Eₖ = ½ m v²
I: Eₖ = 0.5 × 1600 × 15²
F: already the subject
A: 0.5 × 1600 × 225 = 180 000 J
Q2 (F) The car’s battery stores 60 kWh. The car uses 0.15 kWh for each kilometre. Calculate its range.
Show solution
range = energy stored ÷ energy used per km
= 60 ÷ 0.15 = 400 km
Q3 (F) A home charger works at 230 V with a current of 32 A. Calculate its power in kW.
Show solution
F: P = V I
I: P = 230 × 32
F: already the subject
A: 7360 W = 7.4 kW
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Q4 (F) How long does the 7.4 kW charger take to add 37 kWh to the battery?
Show solution
F: E = P t
I: 37 = 7.4 × t
F: t = 37 ÷ 7.4
A: 5.0 hours
Q5 (F/H) The car accelerates from 0 to 27 m/s in 6.0 s. Calculate (a) the acceleration (b) the resultant force needed.
Show solution
(a) a = Δv ÷ t = 27 ÷ 6.0 = 4.5 m/s²
(b) F = m a = 1600 × 4.5 = 7200 N
Q6 (F/H) Charging the 60 kWh battery from empty costs 25p per kWh. Calculate (a) the cost of a full charge (b) the cost per kilometre if the range is 400 km.
Show solution
(a) 60 × £0.25 = £15
(b) £15 ÷ 400 = £0.0375 = 3.75p per km
Q7 (F/H) Describe the energy transfers when an electric car uses regenerative braking to slow down. [3 marks]
Show answer
• Energy is transferred from the car’s kinetic energy store…
• …by the motor acting as a generator, electrically, to the battery’s chemical energy store.
• Some energy is dissipated to the thermal store of the brakes and surroundings, so not all of it is recovered.
Q8 (H) The car is travelling at 25 m/s. The brakes give it a deceleration of 6.25 m/s². Calculate the braking distance.
Show solution
F: v² − u² = 2 a s
I: 0² − 25² = 2 × (−6.25) × s, so −625 = −12.5 × s
F: s = 625 ÷ 12.5
A: 50 m
Q9 (H) The driver’s reaction time is 0.70 s. Calculate the total stopping distance from 25 m/s, using your answer to Q8.
Show solution
Thinking distance: s = v t = 25 × 0.70 = 17.5 m
Stopping distance: 17.5 + 50 = 67.5 m ≈ 68 m
Q10 (H) Electric cars are often heavier than petrol cars of a similar size because of their batteries. Explain the factors that affect the braking distance of a car, including the effect of its mass. [6 marks]
Show answer
Marking points (any 6):
• Braking distance increases with speed – doubling the speed roughly quadruples the braking distance, because kinetic energy ∝ v².
• A larger mass means more kinetic energy at the same speed, so for the same braking force the deceleration (a = F ÷ m) is smaller and the braking distance is longer.
• Wet or icy roads reduce friction between the tyres and the road, so braking distance increases.
• Worn tyres (little tread) reduce grip and increase braking distance.
• Worn brakes produce a smaller braking force, so braking distance increases.
• The work done by the brakes (force × distance) must equal the kinetic energy, so more kinetic energy needs a longer distance for the same force.
⚠️ Where students lose marks
- Forgetting to square the speed in Eₖ = ½ m v².
- Mixing up kW and W, or hours and seconds, in charging questions – keep kWh questions in kW and hours.
- Missing out thinking distance when asked for stopping distance.
- Saying a heavier car “stops faster because it has more grip”. More mass means more kinetic energy to remove, so a longer braking distance.
More devices: all 40 everyday devices · Forces · Energy
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