A wheel of radius 0.4 m can rotate freely about its axis as shown in the figure. A string is wrapped over its rim and a mass of 4 kg is hung. An angular acceleration of $8\;rad-s^{-2}$ is produced in it due to the torque. Then moment of inertia of the wheel is :

Question

 

 

$$\begin {array} {1 1} (1)\;2\;kg-m^{2} & \quad (2)\;1\;kg-m^{2} \\ (3)\;4\;kg-m^{2} & \quad (4)\;8\;kg-m^{-2} \end {array}$$