Thinking & Braking Distances (AQA GCSE Physics)

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Thinking & Braking Distances

  • The stopping distance of a car is defined as:

The total distance travelled during the time it takes for a car to stop in response to some emergency

  • It can be written as an equation involving two distances:

Stopping distance = Thinking distance + Braking distance

  • Where:
    • Thinking distance = the distance travelled in the time it takes the driver to react (reaction time) in metres (m)
    • Braking distance = the distance travelled under the braking force in metres (m)
    • Stopping distance = the sum of the thinking distance and braking distance, in metres (m)

  • For a given braking force, the greater the speed of the vehicle, the greater the stopping distance

Worked example

At a speed of 20 m/s, a particular vehicle had a stopping distance of 40 metres. The car travelled 14 metres whilst the driver was reacting to the incident in front of him. What was the braking distance?

A      54 m

B      34 m

C      26 m

D      6 m

ANSWER:  C

Step 1: Identify the different variables

    • Stopping distance = 40 m
    • Thinking distance = 14 m

Step 2: Rearrange the formula for stopping distance

Stopping distance = Thinking distance + Braking distance

Braking distance = Stopping distance – Thinking distance

Step 3: Calculate and identify the correct braking distance

    • Braking distance = 40 – 14 = 26 metres
    • Therefore, the answer is C

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.