The velocity of small ball of mass `M` and density `d_(1)` when dropped a container filled with glycerine becomes constant after some time. If the density of glycerine is `d_(2)`, the viscous force acting on ball is

Explanation

At equilibrium the viscous forc acting upward =
Effective force downward
Effective force `=Vd_(1)g=Vd_(2)g=V(d_(1)-d_(2))g`
`=M/(d_(1))(d_(1)-d_(2))g=Mg[1-(d_(2))/(d_(1))]`
`[ :' V=M/(d_(1))]`