# A metal sphere of radius 1 mm and mass 50 mg

Question:

A metal sphere of radius $1 \mathrm{~mm}$ and mass $50 \mathrm{mg}$ falls vertically in glycerine. Find

(a) the viscous force exerted by the glycerine on the sphere when the speed of the sphere is $1 \mathrm{~cm} / \mathrm{s}$,

(b) the hydrostatic force exerted by the glycerine on the sphere and

(c) the terminal velocity with which the sphere will moved down without acceleration. Density of glycerine = $1260 \mathrm{~kg} / \mathrm{m}^{3}$ and its coefficient viscosity at room temperature $=8.0$ poise.

Solution: