Question

Spherical balls of radius R are falling in a viscous fluid of viscosity η with a velocity v. The retarding viscous force acting on the spherical ball is

(a) Directly proportional to R but inversely proportional to v 

(b) Directly proportional to both radius R and velocity v 

(c) Inversely proportional to both radius R and velocity v

(d) inversely proportional to R but directly proportional to velocity v

Answer 1

Correct Option (b) Directly proportional to both radius R and velocity v 

Explanation:

Retarding force acting on a ball falling into a viscous fluid

Or in other words, retarding force is directly proportional to both R and v.