Two masses m and 2 m are connected by a light string going over a pulley (disc) of mass 30 m with radius r=0.1 m. The pulley is mounted in a vertical…

Two masses $\displaystyle m$ and $\displaystyle 2$ m are connected by a light string going over a pulley (disc) of mass $\displaystyle 30$ m with radius $\displaystyle r=0.1 \mathrm{~m}$. The pulley is mounted in a vertical plane and it is free to rotate about its axis. The 2m mass is released from rest and its speed when it has descended through a height of $\displaystyle 3.6$ m is $\displaystyle \_\_\_\_$ $\displaystyle \mathrm{m} / \mathrm{s}$. (Assume string does not slip and $\displaystyle \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )