GCSE Physics revision

Factors affecting braking distance 1

Forces and braking

AQA 4.5.6.3.3

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Explain factors affecting emergency stopping distance and their safety implications, and estimate how stopping distance varies with typical vehicle speeds.

MOST 🎯🎯

Apply the scientific explanation of factors affecting braking distance 1 to a relevant example.

SOME 🎯🎯🎯

Analyse a new situation involving factors affecting braking distance 1 and explain the scientific reasoning.

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

Thinking Distance

Thinking distance is the distance the car travels during the driver's reaction time, before the brakes are applied.
Reaction time is the time taken for the driver to spot the obstruction, make a decision, and move their foot to the brake.
Reaction time typically ranges from 0.2 seconds to 0.9 seconds, varying from person to person.

1. Thinking DistanceAQA

Notes

Thinking distance is the distance the car travels during the driver's reaction time, before the brakes are applied.
Reaction time is the time taken for the driver to spot the obstruction, make a decision, and move their foot to the brake.
Reaction time typically ranges from 0.2 seconds to 0.9 seconds, varying from person to person.

Measuring Reaction Time

A ruler drop test can be used to measure reaction time: the further the ruler falls before being caught, the longer the reaction time.
The distance the ruler falls is used to look up the corresponding reaction time from a table.

Factors Affecting Thinking Distance

A tired driver has a longer reaction time than an alert driver, which increases the thinking distance.
Alcohol and certain drugs slow a driver's reactions, increasing reaction time and therefore thinking distance.
Distractions inside the car, such as using a mobile phone, also increase the driver's reaction time and thinking distance.

3. Factors Affecting Thinking DistanceAQA

Notes

A tired driver has a longer reaction time than an alert driver, which increases the thinking distance.
Alcohol and certain drugs slow a driver's reactions, increasing reaction time and therefore thinking distance.
Distractions inside the car, such as using a mobile phone, also increase the driver's reaction time and thinking distance.

Braking Distance

Braking distance is the distance the car travels from when the brakes are applied to when the car stops.
Wet or icy road conditions reduce the friction between the tyres and the road, increasing the braking distance.
Worn tyres reduce the grip between the tyres and the road surface, which increases the braking distance.
Worn brakes are less effective at applying a braking force, which also increases the braking distance.

4. Braking DistanceAQA

Notes

Braking distance is the distance the car travels from when the brakes are applied to when the car stops.
Wet or icy road conditions reduce the friction between the tyres and the road, increasing the braking distance.
Worn tyres reduce the grip between the tyres and the road surface, which increases the braking distance.
Worn brakes are less effective at applying a braking force, which also increases the braking distance.

The Relationship Between Speed and Stopping Distance

As speed increases, both the thinking distance and the braking distance increase, so the overall stopping distance becomes significantly greater.
This means that driving at higher speeds is considerably more dangerous in an emergency situation, as the car needs much more distance to stop safely.

5. The Relationship Between Speed and Stopping DistanceAQA

Notes

As speed increases, both the thinking distance and the braking distance increase, so the overall stopping distance becomes significantly greater.
This means that driving at higher speeds is considerably more dangerous in an emergency situation, as the car needs much more distance to stop safely.