Question

Which of the following is the most accurate statement of the law of conservation of momentum?
The total momentum of a system of objects before and after an interaction is the same, if there are no outside forces acting.
When two objects collide, the momentum of each object stays the same.
The impulse acting on an object is equal to the momentum change it causes on another object.
Momentum is a vector quantity.

Answer 1

The most accurate statement of the law of conservation of momentum is:

The total momentum of a system of objects before and after an interaction is the same, if there are no outside forces acting.

For example, if object A collides with B, it transfers its momentum to object B.