What does the law of conservation of momentum state?

The law of conservation of momentum asserts that the total momentum of a closed system remains constant, provided that no external forces act upon it. This principle is fundamental in physics, particularly in scenarios involving collisions and interactions between objects.

In a closed system, such as two colliding billiard balls on a frictionless table, the momentum before the collision must equal the momentum after the collision. This means that if one object loses momentum, another object gains an equivalent amount of momentum, keeping the total unchanged. This law holds true regardless of the types of interactions taking place, making it a powerful tool for analyzing a wide variety of physical situations.

The concept of external forces is crucial; if an external force does act on a system, it can change the total momentum. Thus, in an isolated system where external influences are absent, the law guarantees that momentum will remain consistent over time.