Two coaxial discs, having moments of inertia
I₁ and I₁/2, are rotating with respective angular
velocities _1 and
₁/2
, about their common axis.
They are brought in contact with each other and
thereafter they rotate with a common angular
velocity. If E_f and E_i are the final and initial total
energies, then (E_f - E_i) is: