Conservation of Linear Momentum

The law of conservation of linear momentum is quite simple: if no net force acts on a physical system, its entire momentum will be conserved. A common way to look at this is through collisions, which are often used in physics and are important in engineering. However, let's first define two types of collisions:

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An elastic collision is one where the objects that collide "bounce" or "rebound" off one another. Another way to state this is that an elastic collision is one where the system's kinetic energy is conserved.

An inelastic collision is one where the objects that collide don't bounce off one another and thus the system's kinetic energy is partially lost. Rather, the objects that collide stick together kind of like Play-Doh if you want to think about it that way(this is easier to visualize if two rolling balls collide but the basic principle still holds for any object).