Q. A
circular disc of mass 10 kg is suspended by a wire attached to its
centre. The wire is twisted by rotating the disc and released. The
period of torsional oscillations is found to be 1.5 s. The radius of
the disc is 15 cm. Determine the torsional spring constant of the
wire. (Torsional spring constant α is defined by the relation J
= –α θ,
where J is
the restoring couple and θ
the angle of twist).