Law of Conservation of Linear Momentum

Newton’s second law of motion states that the rate of change of momentum of a body is directly proportional to the applied force. Hence, in the absence of an external force, there is no change in the momentum of a body. This law is also applicable to a system consisting of several bodies. The members in a many-body system may have interactions among themselves due to collisions, attractions, repulsions, etc. These forces are internal and not external forces.

Conservation Law of Linear Momentum:

In the absence of any external force acting on a system of bodies, even if interactions exist among the bodies, the total linear momentum of the system remains constant.

This statement is the law of conservation of linear momentum. For a system of bodies, we can calculate the components of linear momentum of all the bodies present in any chosen direction. The sum of these individual components in this direction will be a constant.