A uniform disc of radius 5-0 cm and mass 200 g is fixed at its centre to a metal uwire, the other end of which is fixed with a clamp. The hanging disc is rotated about the wire through an angle and is released. If the disc makes torsional oscillations with time period 0-20 s, find the torsional constant of the wire.

A uniform disc of radius 5-0 cm and mass 200 g is fixed at its centre to a metal uwire, the other end of which is fixed with a clamp. The hanging disc is rotated about the wire through an angle and is released. If the disc makes torsional oscillations with time period 0-20 s, find the torsional constant of the wire.