Question

The lower end of a capillary tube of diameter $2.00$mm is dipped $8.00$ below the water surface in a beaker. What is the pressure required in the tube in order to blow a hemisphere bubble at its end in water? Given that density of water $={10}^3$ kg $m^{-3}$, surface tension of water $=7.3\times {10}^{-2}$ N $m^{-1}$ and atmospheric pressure $=1.01\times {10}^5$Pa.

Answer 1

The excess pressure in a bubble of gas in a liquid is given by 2S/r

There is only one liquid surface in this case. Pressure outside the bubble

wy = Atmospheric pressure + pressure due to 8cm of water column

$wy=1.01\times 10gw+0.08\times 1000\times 9.80=1.01784\times 10gw$