Скачать или смотреть Basic Mechanics 08 - conservation of linear momentum

Continuing with our discussion of Newton's second law for a system of particles, I show how this can be rewritten to read that the rate of change of the net linear momentum of a system is equal to the net external force acting on it. A direct corollary of this leads to the law of conservation of linear momentum for a system of particles. I then show how this can be applied to a problem of two colliding bodies.

This leads to a puzzle - just how can we use the law of conservation of momentum to discuss the results of collision between two bodies, despite the presence of external forces? The answer leads us to the concept of impulse and impulsive forces.

I end by posing another puzzle as a challenge to the viewer, by (apparently) proving using the law of conservation of momentum that no gun can ever fire. If you have managed to solve this puzzle, feel free to comment below,