Question

An air bubble of radius 5 $\times$ 10${}^{-4}$m rises in a liquid of viscosity 0.1 Pas (g$=10m{s}^{-2}$) and density 900kgm${}^{-3}$. The terminal velocity of the bubble is:

• A. 0.005ms${}^{-1}$
• B. 0.01ms${}^{-1}$
• C. 0.5ms${}^{-1}$
• D. 0.4ms${}^{-1}$

Answer 1

The correct option is A 0.005ms${}^{-1}$

We know from the formula that,
Terminal Velocity = $\frac{2r^2(T-\sigma )g}{9\eta }$
$\frac{2(5\times {10}^{-4}{)}^2}{9\times 0.1}\times 900\times 10$ [Neglecting the density of air]
$=0.005m{s}^{-1}$