What is the conservation of momentum?

The conservation of momentum is a fundamental law of physics stating that the total momentum of a closed system remains constant.

In more detail, the principle of conservation of momentum is derived from Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. This means that the forces two objects exert on each other are equal in magnitude and opposite in direction. As a result, any changes in momentum experienced by one object are balanced by corresponding changes in the other object, ensuring that the total momentum of the system remains unchanged.

Momentum, in physics, is a vector quantity, meaning it has both magnitude and direction. It is calculated as the product of an object's mass and its velocity. Therefore, if a system is closed, meaning it is not influenced by external forces, the total momentum before an event (like a collision or explosion) must be equal to the total momentum after the event. This is true regardless of the nature of the forces between the objects within the system.

For example, consider two ice skaters pushing off each other in opposite directions. Before they push off, their combined momentum is zero (as they are stationary). After they push off, one skater moves in one direction and the other skater moves in the opposite direction. Each skater now has momentum, but the total momentum of the system (the two skaters) is still zero, as the momentum of one skater is equal in magnitude but opposite in direction to the momentum of the other skater.

The conservation of momentum is a powerful tool in physics. It is used to analyse collisions, explosions, and even the motion of rockets. It is also fundamental in the study of atomic and subatomic particles in quantum mechanics. Understanding and applying the principle of conservation of momentum is crucial for solving many problems in physics.