Question

If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can surely say that

• A. linear momentum of the system does not change in time
• B. kinetic energy of the system does not change in time
• C. angular momentum of the system does not change in time
• D. potential energy of the system does not change in time

Answer 1

Answer: (A)

On a system of particles if, $\Sigma F_{\text{ext. }}=0$
then, $p_{\text{system }}=\text{ constant }$
No other conclusions can be drawn.