Introduction to Conservation of Momentum with Demonstrations

Momentum is defined as mass times velocity, and both are vectors. Conservation of momentum applies to isolated systems, where the net force on the system is zero. This means the initial momentum of the system equals the final momentum of the system.

In physics, conservation of momentum is particularly true during collisions and explosions. An explosion, in this context, refers to a system where its parts move apart from each other.

A demonstration using a skateboard and a medicine ball illustrates conservation of momentum. Initially, the system's total momentum is zero. When the medicine ball is thrown (negative momentum), the person on the skateboard moves in the opposite direction (positive momentum) to conserve the total zero momentum of the system.

The concept is extended to how a rocket works: rocket fuel is ejected quickly downward (negative momentum), causing the rocket to move upward. Similarly, a hose spray nozzle ejects water downward, giving the nozzle an upward momentum.