5.7 - Momentum

• In a closed system, the total momentum before an event is equal to the total momentum after the event. This is called conservation of momentum.
• A collision is when an object transfers momentum to another.
• In a collision, the seat belt stretches. The time it takes for the person held by the seat belt to lose momentum compared to a person not wearing a seat belt, increases. The force on the person's body decreases and so reduces the risk of injury.