Question

Initially two stable particles $x$ and $y$ start moving towards each other under mutual attraction. If at one time the velocities of $x$ and $y$ are $V$ and $2V$ respectively, what will be the velocity of centre of mass of the system?

• A. $V$
• B. Zero
• C. $\frac{V}{3}$
• D. $\frac{V}{5}$

Answer 1

The correct option is B Zero

Since they are moving under mutual force at attraction their internal forces cancel each other and $M\overrightarrow{a_{cm}}=F_{external}\overrightarrow{F_{external}}=0\overrightarrow{a_{cm}}=0Sinceinitialvelocity=0Finalvelocity=0Since\overrightarrow{a}=0$