Free GCSE Physics lesson: Stopping and Momentum
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Free Lessons -> GCSE / Key Stage 4 -> Physics -> Stopping and Momentum

Lesson 16 · GCSE / Key Stage 4 · Physics

Stopping distances and momentum

Calculate momentum, explain stopping distance and connect forces to road safety.

Qualification: GCSE Subject: Physics Safety Separate Physics and Combined Science

Forces

This lesson builds stopping distances, momentum and safety for GCSE Physics.

Use the core lesson first, then match the exam-board guidance to your school route. Many pupils meet this content through Combined Science as well as Separate Physics.

Good forSeparate Physics and Combined Science
FocusStopping distances, momentum and safety
Time45-60 minutes
EquipmentCalculator and road-safety context notes.
Paper fitPaper 2 focus on most GCSE Physics routes
TierFoundation and Higher core
Practical linkNo required practical focus
Maths tagsM1 substitution with units

What you will learn

  • Distinguish thinking distance and braking distance.
  • Explain factors that affect stopping distance.
  • Use momentum = mass x velocity.
  • Explain why longer stopping time reduces impact force.

Exam-board fit

RouteSeparate Physics and Combined Science
PaperPaper 2 focus on most GCSE Physics routes
TierFoundation and Higher core
Specification fitForces: Stopping distances, momentum and safety
Practical linkNo required practical focus
Maths ladderM1 substitution with units

Exact paper labels and specification-point numbering vary by board and cohort, so match this lesson to your school route before using past-paper questions.

Safety scenarios supplied on this page

Use the car, bicycle and collision examples to practise stopping-distance reasoning and momentum calculations.

Clear explanation

Stopping distance is thinking distance plus braking distance. Thinking distance depends on reaction time and speed. Braking distance depends on speed, road conditions, tyres, brakes and mass.

Momentum is mass times velocity. In a closed system, total momentum before a collision equals total momentum after the collision.

Safety features increase the time taken to stop during a collision. For the same change in momentum, a longer stopping time means a smaller average force.

Worked examples

Calculating momentum

A 70 kg cyclist moves at 6 m/s.

momentum = mass x velocity

momentum = 70 x 6 = 420

Answer: The cyclist's momentum is 420 kg m/s.

Quick checks

Choose an answer, then check your thinking.

1. What two parts make stopping distance?

2. A 2 kg object moves at 4 m/s. What is its momentum?

Practice questions

Question 1

A car has thinking distance 12 m and braking distance 28 m. Calculate stopping distance.

Reveal answer and marking guidance

Answer: 40 m.

Marking: Credit adding thinking and braking distances.

Question 2

A 1200 kg car travels at 15 m/s. Calculate momentum.

Reveal answer and marking guidance

Answer: 18 000 kg m/s.

Marking: Credit p = m v and 1200 x 15 = 18 000 kg m/s.

Question 3

Name two factors that increase braking distance.

Reveal answer and marking guidance

Answer: Higher speed and wet or icy roads.

Marking: Credit any two valid factors such as worn tyres, poor brakes, downhill slope or greater mass.

Question 4

Why does an airbag reduce injury risk?

Reveal answer and marking guidance

Answer: It increases the time over which the passenger slows down, reducing the average force.

Marking: Credit longer collision time and reduced force.

Exam practice ladder

AO1 fluencyRecall the key definition, unit, equation or model before using the lesson questions.
AO2 applicationApply stopping distances, momentum and safety to an unfamiliar device, practical setup or data description.
AO3 analysisUse evidence, graph features, uncertainty, method quality or conclusion wording where the question asks you to evaluate.
Maths skillM1 substitution with units

Answers and marking guidance

The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.

Common mistakes

  • Forgetting thinking distance in total stopping distance.
  • Saying momentum is the same as force.
  • Ignoring velocity direction in momentum questions.
  • Claiming safety features reduce momentum change rather than increasing stopping time.

Exam-board guidance

All supported routes assess the core physics idea, but they may group topics, practicals and paper wording differently.

AQA GCSE Physics

AQA GCSE Physics: use this lesson for stopping distances, momentum and safety, then check whether your class is taking Separate Physics or Combined Science.

OCR GCSE Physics

OCR GCSE Physics: the core physics idea is shared, but Gateway and Twenty First Century may organise questions differently.

Pearson Edexcel GCSE Physics

Pearson Edexcel GCSE Physics: practise the concept, the equation use and the practical language because questions often connect them.

Eduqas GCSE Physics

Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.

WJEC Wales

WJEC Wales: check whether your class is using the current GCSE Physics route or a newer science route, then use this lesson for the shared physics idea.

CCEA GCSE Physics

CCEA GCSE Physics: connect the idea to your unit and remember that practical skills are assessed directly.

Extension challenge

Compare two drivers at different speeds and explain why doubling speed more than doubles the danger.

Reveal answer

Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.

Next lesson

Next, continue with Wave Behaviour and Lenses.

Previous lesson: Newton's LawsBack to GCSE Physics lessonsNext lesson: Wave Behaviour and Lenses