A small metal sphere of radius a is falling with a velocity `upsilon` through a vertical column of a viscous liquid. If the coefficient of viscosity of the liquid is `eta`, then the sphere encounters an opposing force of

Options

A. `6 pi eta a^(2)upsilon`
B. `(6eta upsilon)/(pia)`
C. `6pi eta a upsilon`
D. `(pi eta upsilon)/(6a^(3))`

Answer

C

Explanation

Stock estbalished that if a sphere of radius a moves with velocity v through a fluid of viscosity n, the the viscous force opposing the motion of the sphere if `F=6pieta av`