Give an expression for the terminal speed of a small spherical object in a homogenous surrounding fluid.

Explanation

`V_(1)=((2)/(9eta))a^(2)g(p-rho)`
where, `rho`-density of the small spherical object.
`sigma`- density of the surrounding fluid.
`eta`- viscosity of the fluid
a -radius of a spherical object
`v_(t)` - terminal speod of the object.