Q. A non-zero external force acts on a systems of particles. The velocity and acceleration of the centre of mass are found to be $v_{0}$ and $a_{0}$ at an instant $t$. It is possible that
A) $v_{0} = 0,a_{0} = 0$
B) $v_{0} = 0,a_{0} \neq 0$
C) $v_{0} \neq 0,a_{0} = 0$
D) $v_{0} \neq 0,a_{0} = 0$
Explanation
(b) If external force is non-zero then acceleration of centre of mass must be non-zero $\left( a_{0} = \frac{F_{ext}}{M} \neq 0 \right)$. However, at a particular instant of time velocity of centre of mass may be zero or non-zero. Hence option (b) is correct.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.