Correct Answer - (a) `(mg cos omegat)/(Bb)`; (b) `(Bomegab^(2))/(2) + (mg R cos omega t)/(Bb)`
(a) `tau_(B) = F_(B) xx (b)/(2) rarr tau_(B) = IbB xx (b)/(2) = IB(b^(2))/(2)`
`tau_(net) = 0 `rarr` mg cos theta xx (b)/(2) = (IBb^(2))/(2)`
`rarr` `mg cos theta = IBb`
`theta = omegat`
`rarr` `I = (mg cos omegat)/(Bb)`
(b) `((E - E_(i nd)))/(R) = I`, `E = E_(i nd). + IR`
`rarr` `E = (Bomegab^(2))/(2) + (mg R cos omegat)/(Bb)`