One end of a metal wire is fixed at the centre of a uniform disc of radius 4.0 cm and mass 100 g. The other end of the wire is fixed with a clamp.…

One end of a metal wire is fixed at the centre of a uniform disc of radius $\displaystyle 4.0$ cm and mass $\displaystyle 100$ g. The other end of the wire is fixed with a clamp. The hanging disc is rotated about the wire through a small angle and is released. If the disc makes torsional oscillations with time period $\displaystyle 0.20$ s, the torsional constant of wire is (Given $\displaystyle \pi^2=10$ )