An air bubble of radius $r$ rises steadily through a liquid of density $\rho $ with velocity $v$ . The coefficient of viscosity of liquid is
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Steady motion $\Rightarrow \mathrm{a}=0$
$\mathrm{F}_{\mathrm{net}}=0$
$\mathrm{F}_{\mathrm{v}}=\mathrm{F}_{\mathrm{B}}$
$6 \pi \eta r v=\rho \cdot \frac{4}{3} \pi r^{3} g$
$\eta=\frac{2}{9} \frac{\rho r^{2} g}{v}$
$Method \,II:$ Dimensional analysis.
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