Question

When two objects collide their momentum after the collision is explained by what law?

Answer 1

When two objects collide their momentum change is explained by

Newton's Third law - Every action has equal and opposite reaction

Answer 2

The law of momentum conservation can be stated as follows. For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.