The law of momentum is one of the universal theorems of dynamics. It states that the increment of an object's momentum is equal to the impulse of the total external force it receives, that is, Ft=Δvm, or the vector sum of the impulses of all external forces. If a system is not subject to external forces or the vector sum of the external forces it receives is zero, then the total momentum of the system remains unchanged. This conclusion is called the law of conservation of momentum. The law of conservation of momentum is one of the most important and universal conservation laws in nature. It applies to both macroscopic objects and microscopic particles; to both slow-moving objects and high-speed moving objects. It is an experimental law and can also be derived from Newton's second law and the law of kinetic energy.

Momentum: ΔM＝F*ΔT

F = Force

ΔT = change in time