Question
An air bubble of radius 1.0 mm rises with uniform velocity through a viscous liquid of density 1625 kg/m^{3}. Calculate the velocity of the bubble if the coefficient of viscosity of the liquid is 10 poise and the density of air is negligible. (g = 10 m/s^{2}).

None of these



medium
Solution
The bubble is of air, hence its weight is negligible. Now, two forces act upon the rising bubble
(i) Upthrust of the liquid, (downward), where t is the radius of the bubble and is the density of liquid.
(ii) Viscous force, (downward), where is coefficient of viscosity of the liquid and v is the velocity of the bubble.
The bubble is rising upward with uniform velocity, hence net force on it is zero, that is
.
.
. Putting this and other given values
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