Question

A circular disc of radius \(15\,cm\) and mass \(10\,kg\) is suspended by a wire attached to its centre. When the wire is twisted by rotating the disc and released, the period of torsional oscillations of the disc is \(1.5\,s\). The torsional spring constant of the wire is nearly:

• A. \(2\,Nm\,rad^{-1}\)
• B. \(3\,Nm\,rad^{-1}\)
• C. \(4\,Nm\,rad^{-1}\)
• D. \(1\,Nm\,rad^{-1}\)

Hint:

For torsional oscillations: \[ T=2\pi\sqrt{\frac{I}{C}}. \] This is analogous to the spring formula \[ T=2\pi\sqrt{\frac{m}{k}}. \]

Answer 1

The Correct Option is A