What does the principle of conservation of momentum state?

The principle of conservation of momentum asserts that in a closed system, where no external forces are acting, the total momentum remains constant over time. This fundamental principle indicates that if two or more bodies collide or interact in some way, their combined momentum before the interaction will be equal to their combined momentum after the interaction, provided that no outside forces interfere.

This means that the total momentum calculated by summing the individual momenta of all objects involved will not change, thus preserving the overall momentum in that closed system. For example, in a collision between two cars on a frictionless surface, the momentum before collision will equal the momentum after collision, so long as no external forces like friction or air resistance come into play.

Understanding this principle is crucial in various fields, including physics and engineering, as it helps explain a wide range of phenomena, from everyday situations like sports to complex interactions in particle physics.