A pulley fixed to the ceiling carries a string with blocks of mass `m` and `3m` attached to its ends. The masses of string and pulley are negligible .When the system is released, its center of mass moves with what acceleration

Options

A. 0
B. `-g//4`
C. `g//2`
D. `-g//2`

Answer

C

Explanation

When the system is released, heavier mass move downward and the lighter one upward. Thus, centre of mass will move towards the heavier mass with acceleration
`a=((3m-m)/(3m+m))g=(g)/(2)`