This topic summary covers Knowledge Organiser: Stopping Distances within Stopping Distances for GCSE Physics. Revise Stopping Distances in Forces for GCSE Physics with 15 exam-style questions and 5 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Stopping Distances
Key Terms
- Thinking distance: Distance during reaction time
- Braking distance: Distance while brakes applied
- Stopping distance: Thinking + braking distance
- Reaction time: Time to respond to hazard
Key Facts
- Thinking distance ∝ v (linear)
- Braking distance ∝ v² (squared)
- Thinking: affected by driver (drugs, fatigue)
- Braking: affected by car/road (tyres, conditions)
Key Equations
- Stopping = Thinking + Braking
- Thinking distance = speed × reaction time
- Braking ∝ v² (from KE = ½mv²)
Exam Tips
- Doubling speed: thinking ×2, braking ×4
- Always link braking distance to KE = ½mv²
- State "driver" factors for thinking, "car/road" for braking
- Wet road → more braking distance (less friction)
Common Mistakes
- Thinking doubling speed doubles braking distance: Braking distance is proportional to v² — doubling speed quadruples braking distance (because KE = ½mv²)
- Confusing thinking distance and braking distance factors: Thinking distance is affected by driver factors (tiredness, drugs, distractions); braking distance is affected by vehicle and road conditions (tyres, brakes, road surface)
- Not linking braking distance to kinetic energy: Examiners expect you to state that larger KE requires more work done by brakes to stop — mention W = F × d and KE = ½mv²
- Saying wet roads affect thinking distance: Wet or icy roads affect braking distance (less friction), not thinking distance — thinking distance depends only on reaction time
- Forgetting large decelerations are dangerous: A very large braking force causes large deceleration — this can cause skidding and loss of vehicle control
Practice questions for Stopping Distances
What is the correct definition of stopping distance?
Explain why a car travelling at higher speed has a greater braking distance than a car travelling at lower speed, assuming the same braking force.
Quick recall flashcards
🧠 Factors Affecting THINKING Distance
Alcohol — impairs judgment and reactions
🧠 Factors Affecting THINKING Distance
Tiredness — slower brain processing