Question

11.A circular disc of moment of inertia It is rotating in a horizontal plane, about its symmetry axis, with a constant angular speed ωi. Another disc of moment of inertia Ib is dropped coaxially onto the rotating disc. Initially the second disc has zero angular speed. Eventually both the discs rotate with a constant angular speed ωf. The energy lost by the initially rotating disc to friction is : 1) (1/2)[Ib2/(It+Ib)] ωi2 2) (1/2)[It2/(It+Ib)] ωi2 3) [(Ib-It)/(It+Ib)] ωi2 4) (1/2)[(Ib-It)/(It+Ib)] ωi2

Answer 1