Question

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

a. may move b. may accelerate

c. must not move d. must not accelerate

• A. a & b are correct
• B. b & c are correct
• C. c & d are correct
• D. a & d are correct

Answer 1

The correct option is D

a & d are correct

If the net external force acting on a system is zero , i.e., ${\overrightarrow{F}}_{net}=0$,the system may be at rest or moving

with uniform velocity. But it will not accelerate, because

${\overrightarrow{F}}_{net}=M{\overrightarrow{a}}_{cm}$

$\Rightarrow$ ${\overrightarrow{a}}_{cm}=\frac{{\overrightarrow{F}}_{net}}{M}=\frac{0}{M}=0$