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

The correct option is A linear momentum of the system does not change in time

We know that Newton's second law is valid in an inertial frame and the law states that,

Linear momentum remains constant if net external force on the system of particles is zero.

$F_{resultant}=\frac{dP}{dt}$

Hence, since $F_{resultant}=0$, we can say that momentum of system will not change with time.