Two identical drops of water are falling through air with a steady speed of .V. each . If the drops coalesce to from a single drop, what is the new terminal velocity ?

Explanation

From conservation of mass , `4/3 pi R^3 xx rho = 4/3 pi r^3 xx rho + 4/3 pi r^3 xx rho`
(or) R`=(2^(1//3)) r. and V_(T) prop r^2 ` (stokes law) `(V^1)/(V) = (R^2)/(r^2) = 2^(2//3) therefore V^1 = 2^(2//3) V`.