Class 11 NEET Physics System of Particles and Rotational Motion

A circular disk of moment of inertia It is rotating in a horizontal plane, about its symmetry axis, with a constant angular speed ωi.Another disk of moment of inertia Ib is dropped co-axially Ib is dropped coaxially onto the rotating disk. Initially the second disk has zero angular speed. Eventually both the disks rotate with a constant angular speed ωf.The lost by the initially rotating disc to friction is