The viscous drug on a sphere of medis, moving through a fluid with velocity can be expressed as` 6 pi eta ` where `eta` is the coefficient of viscosity of the fluid. A small sphere of radius a and density ` sigma ` is released from the bottom of a column of liqaid of density `rho`. If `rho` ger than `sigma` describe the motion of the sphere. Deduce an expression for
(i) initial acceleration of the sphere and
(ii) its terminal velocity