What earns the marks for Topic 2 – Motion and forces in Physics Pearson Edexcel GCSE?

Uses work done = force × distance and equates it to the initial kinetic energy ½ × m × v² to link braking force, braking distance and speed. Rearranges the relationship to give braking distance = (m × v²) ÷ (2 × F) and substitutes consistent SI values. Calculates kinetic energy or work done correctly, for example ½ × 1200 × 20² = 240 000 J for a 1200 kg car at 20 m/s. Shows that doubling the initial velocity quadruples the braking distance because the velocity is squared while mass and braking force stay constant. States the final answer with the correct unit, such as joules for work done...

What mistakes do students make with Topic 2 – Motion and forces?

Squares the velocity but forgets the factor of ½ in the kinetic energy. Include ½ × m × v² in the calculation. Doubles the braking distance when the speed doubles. Recognise that squaring the velocity quadruples the distance. Mixes units such as grams with kilograms or kilometres per hour with metres per second. Convert all quantities to SI before substituting.

What are the exam tips for Topic 2 – Motion and forces in Physics Pearson Edexcel GCSE?

Write the equation F × d = ½ × m × v² before substituting so the examiner sees the link between work done and kinetic energy. Convert mass to kilograms and speed to metres per second first, then substitute to avoid unit errors. When asked to show the squared dependence, compare two speeds such as v and 2v and state the ratio of distances explicitly.

Pearson Edexcel · GCSE · Physics

Course version: 1PH0 · Version from Sept 2016

2.33P Carry out calculations on work done to show the dependence of…

Full specification wording

Topic 2 – Motion and forces: 2.33P Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy)

This specification point asks you to calculate the work done in stopping a vehicle and to use that result to show why braking distance grows with the square of the initial velocity.

Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on 2 November 2026.

Point 32 of 32

Study notes

From the checked teaching notes for this specification point.

The idea

This specification point asks you to calculate the work done in stopping a vehicle and to use that result to show why braking distance grows with the square of the initial velocity. The braking force does work over the braking distance, and this work equals the vehicle's initial kinetic energy, so F × d = ½ × m × v². Rearranging gives d = (m × v²) ÷ (2 × F). Because v is squared, doubling the speed quadruples the braking distance for the same mass and braking force. For example, a 1200 kg car at 10 m/s has kinetic energy ½ × 1200 × 10² = 60 000 J; at 20 m/s it has 240 000 J, four times as much, so it needs four times the distance to stop. Work through the numbers, keep units in joules, kilograms, metres per second and metres, and state the squared relationship explicitly.

What earns the marks

Uses work done = force × distance and equates it to the initial kinetic energy ½ × m × v² to link braking force, braking distance and speed.
Rearranges the relationship to give braking distance = (m × v²) ÷ (2 × F) and substitutes consistent SI values.
Calculates kinetic energy or work done correctly, for example ½ × 1200 × 20² = 240 000 J for a 1200 kg car at 20 m/s.
Shows that doubling the initial velocity quadruples the braking distance because the velocity is squared while mass and braking force stay constant.
States the final answer with the correct unit, such as joules for work done or metres for braking distance.

Common mistakes and how to put them right

Squares the velocity but forgets the factor of ½ in the kinetic energy.
Put it right: Include ½ × m × v² in the calculation.
Doubles the braking distance when the speed doubles.
Put it right: Recognise that squaring the velocity quadruples the distance.
Mixes units such as grams with kilograms or kilometres per hour with metres per second.
Put it right: Convert all quantities to SI before substituting.

Exam tips

Write the equation F × d = ½ × m × v² before substituting so the examiner sees the link between work done and kinetic energy.
Convert mass to kilograms and speed to metres per second first, then substitute to avoid unit errors.
When asked to show the squared dependence, compare two speeds such as v and 2v and state the ratio of distances explicitly.

Try the lesson

The start of the Topic 2 – Motion and forces: 2.33P Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy) lesson, made from checked teaching notes for this specification point.

Have a go first

A car of mass 800 kg is travelling at 10 m/s. The brakes do work to bring the car to rest. Using the idea that the work done by the brakes equals the car's initial kinetic energy, calculate the work done by the brakes.

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