AQA GCSE Physics

Revision Notes

5.9.4 Force & Momentum

Higher Tier Only

Force & Momentum

  • When a force acts on an object that is moving, or able to move, the object will accelerate (or decelerate)
    • This causes a change in momentum
  • More specifically, the force is the rate of change in momentum

Force and momentum equation, downloadable AS & A Level Physics revision notes

  • Δt is the change in time, or the time taken for the force to change
  • Where the change in momentum is defined as

Final momentum – Initial momentum

  • Force and momentum are vectors so they can be either positive or negative values

Exam Tip

Maths Tip: Remember ‘rate of change’ describes how one variable changes with respect to another

In maths, how fast something changes with time is represented as dividing by Δt (e.g. acceleration is the rate of change in velocity)

More specifically, Δt is used for finite and quantifiable changes such as the difference in time between two events

WE - Tennis ball contact time content part, downloadable AS & A Level Physics revision notes

Higher Tier Only

Calculating Force & Momentum

  • The force and momentum equation can be derived from Newton’s Second law and the definition of acceleration

Worked Example

A tennis ball hits a racket with a change in momentum of 0.5 kg m/s.

For the different contact times, which tennis racket experiences more force from the tennis ball?

WE - Tennis ball contact time answer image, downloadable AS & A Level Physics revision notes

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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.
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