Question

Internal forces do not affect the conservation of momentum because (a) they cancel each other, (b) their effects are canceled by external forces, (c) they can never produce a change in velocity, (d) newton's second law is not applicable to them.

Answer 1

The best answer is C. They can never produce a change in velocity. This question is best described as the "Newton's Cradle Law". For Newton's Cradle Law, it neglects the energy losses but the velocity, momentum and energy of the first object, once strike the second object, will just be transferred if they have the same weight and equal efficient elasticity. It will never produce a change in velocity but it will be just transferred.

Answer 2

Option A. Internal forces do not affect the conservation of the moment because they cancel each other. A system of particles subjected to external forces and also interact with each other, meet the internal forces Newton's third law and those internal forces are canceled and the moment is preserved.