Key idea: A force acting on an object for some time changes its momentum. Force is the rate of change of momentum.
Key relationships (Higher tier):
- Force = Change in momentum ÷ Time (F = Δp ÷ t), with force in newtons (N) and time in seconds (s)
- Change in momentum = Force × Time (Δp = F × t), measured in kg m/s
- Change in momentum = Final momentum − Initial momentum (Δp = mv − mu), measured in kg m/s
The crucial insight:
- For the same change in momentum, increasing the time decreases the force
- F = Δp ÷ t → longer time = smaller force
- This is why safety features work!
This key facts covers Force and Change in Momentum within Force & Collisions for GCSE Physics. Revise Force & Collisions in Forces for GCSE Physics with 10 exam-style questions and 10 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 2 of 7 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Force & Collisions
Which equation links force, change in momentum and time?
Explain how an airbag reduces the risk of injury to a driver in a collision.
Quick recall flashcards
Force and Change in Momentum
Change in momentum = final momentum minus initial momentum (Δp = mv − mu), measured in kg m/s
Force and Change in Momentum
Change in momentum = force × time (Δp = F × t)