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An air bubble of radius 0.2 mm is situated just below the water surface. Calculate the gauge pressure. Surface tension of water = 7.2 x10-2 N/m.

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Explaination::

Given : Radius of bubble =0.2 mm =$$2\times 10^{-4} m$$  , surface tension of water = 0.072 N/m = $$720\times 10^{-4} N/m$$

We know that, excess pressure inside a air bubble in a liquid is given by

Where, t = surface tension of liquid r = radius of bubble

Thus,

The gauge pressure = $$2\times 720\times 10^{-4}\over 2\times 10^{-4}$$ = 720 N/m2

by Expert (11.5k points)