A small metal ball falls in liquid with a terminal velocity of V. If a ball of radius twice of first ball but same mass falls through a same medium, calculate the terminal velocity with which it falls.

Explanation

Given `v = (2r^(2)rhog)/(9eta)`
mass `= 3/4 pi r^(3) rho = 4/3 pi (2r)^(3)rho_(1)` or `rho_(1) = (rho)/(8)`
Terminal velocity of second ball is
`v_(1) = (2(2r)^(2)(rho/8)g)/(9eta) = v/2`
`v_(1) = v/2`