Estimating Decelerating Forces (AQA GCSE Physics)

Revision Note

Test yourself
Ashika

Author

Ashika

Last updated

Estimating Decelerating Forces (HT only)

  • The work done by the brakes when a vehicle slows to a halt is given by the following equation:

Estimating Decelerating Forces, downloadable IGCSE & GCSE Physics revision notes

This equation shows the work done (energy transferred) by the brakes on the wheels of a car

  • This equation shows that:
    • The work done is the transfer of kinetic energy
    • The braking distance is proportional to the speed squared (if the speed is doubled, the distance increases 4 times)

  • We can use this equation to estimate the decelerating forces required for a typical vehicle moving at everyday speeds

Worked example

At 18 m/s (40 mph) the braking distance of a typical car of mass 1500 kg is about 24 m.Use this information to estimate the braking force for a typical car. 

Examiner Tip

You should be able to deduce from the equation that the braking distance is proportional to the vehicle's speed2. Note, this actually doesn't apply at very high speeds because the brakes get hot and become less effective. This reduces the braking force, causing the braking distance to increase even further.

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

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.