A circular disc of moment of inertia `I_(t)` is rotating in a horizontal plane about its symmetry axis with a constant angular velocity `omega_(i)`. Another disc of moment of inertia `I_(b)` is dropped co-axially onto the rotating disc. Initially, the second disc has zero angular speed. Eventually, both the discs rotate with a constant angular speed `omega_(f)`. Calculate the energy lost by the initially rotating disc due to friction.

Options

A. `1/2 I_b^2/((I_t + i_b))omega_i^2`
B. `1/2 I_t^2/((I_t +I_b))omega_i^2`
C. `(I_b - I_t)/((I_t + I_b))omega_u^2`
D. `1/2 (I_b I_t)/((I_t+I_b))omega _i^2`

Answer

D