A disc of moment of inertia \(I_{1}\) is rotating in horizontal plane about an axis passing through a centre and perpendicular to its plane with constant angular speed \(\omega_{1}\). Another disc of moment of inertia \(I_{2}\) having zero angular speed is placed coaxially on a rotating disc. Now both the discs are rotating with constant angular speed \(\omega_{2}\). The energy lost by the initial rotating disc is
1
\(\dfrac {1}{2}\left [\dfrac {I_{1} + I_{2}}{I_{1}I_{2}}\right ]\omega_{1}^{2}\)
2
\(\dfrac {1}{2}\left [\dfrac {I_{1} I_{2}}{I_{1} - I_{2}}\right ]\omega_{1}^{2}\)
3
\(\dfrac {1}{2}\left [\dfrac {I_{1} - I_{2}}{I_{1}I_{2}}\right ]\omega_{1}^{2}\)
4
\(\dfrac {1}{2}\left [\dfrac {I_{1} I_{2}}{I_{1} + I_{2}}\right ]\omega_{1}^{2}\)