Two masses ${\text{m}}_{\text{1}}=10\text{kg}\text{and}{\text{m}}_{\text{2}}=5\text{kg}$ are connected by an ideal string as shown in figure. The coefficients of friction between${\text{m}}_{\text{1}}$ and the surface is$\mu =0.2$ . Assuming that the system is released from rest. The velocity of blocks in${\text{ms}}^{-1}$ when ${\text{m}}_{\text{2}}$  has descended by 4m is $\left[\text{g}=10{\text{ms}}^{-2}\right]$