When two simple harmonic motions of same periods, same amplitude, having phase difference of $3\pi /2$, and at right angles to each other are super imposed. The resultant wave form is a:

A particle of mass 200 g executes linear simple harmonic motion with an amplitude 10 cm. When the particles at a point midway between the mean and the extreme position, its kinetic energy is $3{\pi }^2\times 10^{-3}J$. Assuming the initial phase to be $\frac{2\pi }{3}$, the equation of motion of the particle will be :