The value of the momentum of a system is the same at a later time as at an earlier time if there are no
A) collisions between particles within the system.
B) inelastic collisions between particles within the system.
C) changes of momentum of individual particles within the system.
D) internal forces acting between particles within the system.
E) external forces acting on particles of the system.

Question

Quizplus · Accepted Answer

The value of the momentum of a system remains constant (is conserved) if there are no external forces acting on the system. This is a direct consequence of Newton's third law of motion and the principle of conservation of momentum. Internal forces, regardless of their nature (collisional or non-collisional), do not change the total momentum of the system; it is the external forces that can change the system's total momentum.

The Value of the Momentum of a System Is the Same