In the system shown, block A is of mass 4.0 kg and blocks B and C are of equal mass each of 3 kg. Find the acceleration in m/s² of block C, if the system is set free. $\left[g=10\mathrm{m}/{\mathrm{s}}^2\right]$

F.B.D. of the blocks A, B and C

Conditions of forces on B and C arc same so they both will move with same downward acceleration a. The block A moves with the same acceleration a upwards

 $\mathrm{From} \mathrm{block} \mathrm{A}:$ $2T-40=4a$   …….(i)

$\text{ From block }B\text{ or }C:30-T=3a$  ……..(ii)

$\text{ From above two equations }a=2\mathrm{m}/{\mathrm{s}}^2$