Question

Explain how the conservation of momentum is a consequence of Newton's third law.

Answer 1

Newton's Second Law says that Force = mass × acceleration. Since acceleration is the change in velocity per unit time, F ∝ mΔv, which is to say that force is proportional to change in momentum.

Newton's Third Law says that every force is balanced by an equal and opposite reaction force. Since force is proportional to change in momentum, a change in momentum must also be balanced by an equal and opposite change in momentum. Hence, the conservation of momentum is a consequence of Newton's Third Law.