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.

${\overrightarrow{F}}_{ex}=0\Rightarrow \frac{d\overrightarrow{P}}{dt}=0\Rightarrow \overrightarrow{P}=constant$