GCSE Physics · Edexcel 1PH0 · Topic 2C
Momentum
Key points
- Momentum is mass × velocity: , measured in kg m/s. It is a vector, so direction matters (use + and − for opposite directions).
- In a closed system the total momentum before an event equals the total momentum after it (conservation of momentum).
- Use conservation of momentum for collisions and explosions: add up for each object before and after.
- Force equals the rate of change of momentum: (higher tier).
- Increasing the time of a collision reduces the force. This is how crumple zones, airbags, seat belts and cycle helmets protect people.
- In an explosion from rest the total momentum is zero, so the pieces move off in opposite directions with equal-sized momenta.
Topic notesPremium
Momentum combines mass and velocity into one quantity that is conserved in every collision and explosion. It explains why seat belts and airbags save lives and lets you predict what happens after two objects collide. (Higher tier) In this…
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Momentum.