An air bubble of radius $0.1$ cm lies at a depth of $20$ cm below the free surface of a liquid of density $1000\, ext{kg/m}^3$. If the pressure inside the bubble is $2100\, ext{N/m}^2$ greater than the atmospheric pressure, then the surface tension of the liquid in SI unit is (use $g=10\, ext{m/s}^2$)

Question

An air bubble of radius $0.1$ cm lies at a depth of $20$ cm below the free surface of a liquid of density $1000\,	ext{kg/m}^3$. If the pressure inside the bubble is $2100\,	ext{N/m}^2$ greater than the atmospheric pressure, then the surface tension of the liquid in SI unit is (use $g=10\,	ext{m/s}^2$)

Dr. Abubacker · Accepted Answer

[Solution by Dr. Abubacker] Excess pressure $=\rho gh+\frac{2T}r$: $2100=1000\cdot10\cdot0.2+\frac{2T}{10^{-3}}$, so $\frac{2T}{10^{-3}}=100\Rightarrow T=0.05$ N/m. Answer (2).

Explanation

Reviewed by Dr. Abubacker

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