What is the terminal velocity of a glass ball falling through a tall jar containing glycerine? The densities of the glass ball and glycerine are $8.5\;g/cc$ and $1.32 \;g/cc$ respectively and the viscosity of the glycerin is $0.85\;poise$ and radius of the glass ball is $2\;mm$.

Given,
Density of glass $(\rho) = 8.5\;g/cc = 8500\;kg/m^3$
Density of the glycerin $(\sigma) = 1.32\;g/cc = 1320\;kg/m^3$
Viscosity of glycerin $(\eta) = 0.85\;poise = 0.085 \; decapoise$
Radius of the ball $(r) = 2\;mm = 2 * 10^{-3}\;m$
Terminal Velocity $(v) = ?$

We know,

$v = \frac{2\; r^2 \; (\rho \; - \; \sigma)\;g}{9\; \eta} = \frac{2 \; * \; (2 \; * \; 10^ {-3})^2 \; * \; (8500 \; - \; 1320) \; 10}{9 \; * \; 0.085}$  $= 0.75 \; m/s$

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