The small sphere A has mass m and is fixed at the end of the arm OA of negligible mass, wh...

The small sphere A has mass m and is fixed at the end of the arm OA of negligible mass, which is pinned at O. If the linear elastic spring has stiffness k, determine the equation of motion for small oscillations, using

(a) the vertical position of the mass A as the position coordinate,

(b) the angle formed by the arm OA with the horizontal as the position coordinate.

Figure P9.18