Question

A pulley fixed with celling 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 centre of mass moves with acceleration –

• A. g
• B. g/s
• C. g/4
• D. Zero

Answer 1

Answer: (C)

g/4

Answer 2

Acceleration of each mass w.r.t. pulley

= $\frac{3mg–mg}{(3m + m)}$ = g/2

Acceleration of centre of mass

= $\frac{(3m)\frac{g}{2}–m\frac{g}{2}}{(3m + m)}$= g/4