Question

The diameter of an air bubble which was initially 2 mm, rises steadily through a solution of density 1750 kg m–3 at the rate of 0.35 cms–1. The coefficient of viscosity of the solution is _______ poise (in nearest integer). (The density of air is negligible).

Answer 1

F=6 πηrv
$\frac{4}{3}$πr3ρlg=6 πηrv
η=$\frac{2r^2ρlg}{v}$=$\frac{2×2×10^{−3}×1750×10}{9×3.5×10^{−3}×4}$
=11 poise