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What is momentum in physics?

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Quick answer

Momentum is a measure of how much motion an object has — it depends on both its mass and its velocity. A heavy, fast object has lots of momentum and is hard to stop. In a closed system, total momentum is always conserved.

Key things to understand

  1. Momentum = mass × velocity.
  2. More mass or speed means more momentum.
  3. It measures how hard something is to stop.
  4. Total momentum is conserved in collisions.

People also ask

What is momentum?
A measure of an object's motion, equal to its mass times its velocity.
What is conservation of momentum?
In a closed system with no outside forces, the total momentum stays the same before and after a collision.
Why is a truck harder to stop than a bike?
It has far more mass, so at the same speed it carries much more momentum.

Part of the guide: Cars, Trains, Planes & Ships →