Conservation of Momentum (OCR GCSE Physics A (Gateway Science Suite)): Revision Notes
5.9.2 Conservation of Momentum
Conservation of Momentum
In a closed system, the total momentum before an event is equal to the total momentum after the event. This principle is known as the conservation of momentum.
Example:
Consider two footballs with the same mass, . One football is stationary, while the other is moving at a velocity of .
The momentum before they collide is just the sum of the momentum of each ball:
total momentum before =
Total momentum before =
So the total momentum before the collision is just the momentum of the moving ball because the other ball is not moving and so has no momentum.
After the collision, the total momentum remains Ball B, which was initially stationary, now has velocity and momentum, while ball A moves with a reduced velocity. The sum of these two momentums after the collision will still equal the total momentum before the collision,