Q. A horizontal disk, having a rotational inertia I 1 = 0.61 kg m 2 , placed parallel to, and onto a smooth horizontal plan. Is spinning at an angular speed of w 1 = 22 rad/s . Another disk, with rotational inertia I 2 =0.44kg m 2 spinning at an angular speed w 2 = 32 rad/s is carefully lower onto the first disk so that they are coaxial. As a result of the friction between their surfaces, after a while, both disks spin at the similar angular speed. Determine the work done by the frictional torque. (Sign is important)