Question

There is an air bubble of radius $1.0mm$ in a liquid of surface tension $0.075N/m$ and density $1000kg/m^3$ The bubble is at a depth of $10cm$ below the free surface. By what amount is the pressure inside the bubble greater than the atmospheric pressure? (Take $g=9.8m/s^2)$

Answer 1

Given : Depth of air bubble below the water surface $h=10cm=0.1m$

Radius of air bubble $R=1mm=0.001m$

Surface tension of water $S=0.075N/m$

Excess pressure inside the air bubble $\Delta P=\rho gh+\frac{2S}{R}$

$\therefore$ $\Delta P=1000\times 9.8\left(0.1\right)+\frac{2\left(0.075\right)}{0.001}=1130N/m^2$