Question $3.$

A thin disk of mass $0\mathrm{.}8$ kg and radius $60$ mm is attached to the end of a $1\mathrm{.}2$ m steel

$\frac{N}{m^2},$ density is $7500k\frac{g}{m^3})$ shaft of diameter $20$ mm $.$ The disc is subjected to a harmonic

torque of amplitude $12\mathrm{.}5$ Nm at a frequency of $700ra\frac{d}{s}.$ What is the steady state amplitude

of angular oscillations of the disk?

$[$Ans: $2\mathrm{.}24]$