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

A particle executes a simple harmonic motion of amplitude $$\mathrm{A}$$. The distance from the mean position at which its kinetic energy is equal to its potential energy is

The phase difference between displacement and velocity of a particle in simple harmonic motion is