Oscillation

Define point of oscillation. Show that the point of suspension and point of oscillation are interchangeable in bar pendulum.

A wire has a torsional constant of $2\,\mathrm{Nm/rad}$. A disk of radius $r = 5\,\mathrm{cm}$ and mass $m = 100\,\mathrm{g}$ is suspended at its center. What is the time period of torsional oscillations?

Derive an expression for time period of compound pendulum in terms of equivalent length of simple pendulum and hence define the point of oscillation.