An object of mass 10 g executes SHM along the $x$-axis with frequency of $\left(\frac{10}{\pi}\right) \mathrm{Hz}$. At the point $x=2 \mathrm{~cm}$ the object has KE 1.2 J and PE 0.4 J . The amplitude of oscillation is

A body is executing SHM. When its displacements from the mean position are $$4 \mathrm{~cm}$$ and $$5 \mathrm{~cm}$$ it has velocity $$10 \mathrm{~cms}^{-1}$$ and $$8 \mathrm{~cms}^{-1}$$ respectively. Its periodic time $$\mathrm{t}$$ is

A circular disc of mass $$20 \mathrm{~kg}$$, having radius $$10 \mathrm{~cm}$$ is suspended by a wire attached to its centre. The wire is twisted by rotating the disc and released. The time period of torsional oscillations is found to be $$1 \mathrm{~s}$$. The torsional spring constant of the wire is