Question

If the resultant of all external forces is zero, then velocity of centre of mass will be

• A. zero
• B. constant
• C. either $\left(a\right)$ or $\left(b\right)$
• D. neither $\left(a\right)$ nor $\left(b\right)$

Answer 1

The correct option is B constant

$F_{external}=M{a}_{CM}$ where M is the total mass.

Zero net external force implies that $a_{CM}=0$

Thus $V_{CM}=constant$ OR zero

(If the system is at rest initially, then $V_{CM}=0$)