Linear momentum is a physical quantity that describes the motion of an object. It is calculated by multiplying an object's mass by its velocity, represented by the formula p = mv, where p is momentum, m is mass, and v is velocity. Momentum is a vector quantity, meaning it has both magnitude and direction, and it is conserved in isolated systems, meaning the total momentum before and after an event remains constant. In practical terms, linear momentum helps us understand how objects interact during collisions. For example, when two cars collide, the total momentum of the system (both cars) before the collision equals the total momentum after the collision, assuming no external forces act on them. This principle is crucial in fields like physics, engineering, and sports science.