Question

If the external forces acting on a system have zero resultant, the cenrre of mass

• A. May move but not accelerate
• B. May accelerate
• C. Must not move
• D. None of the above

Answer 1

The correct option is A May move but not accelerate

Acceleration of center of mass $a_{cm}=\frac{F_{external}}{M_{cm}}$

From $F_{external}=0$, we get $a_{cm}=0$

Thus the acceleration of center of mass must be zero when no external force is acting on the system.

So, the center of mass either can be at rest or move with constant velocity but it must not accelerate.