Fluid Mechanics

Water rises upto a height of \(4 \mathrm{~cm}\) in a capillary tube. The lower end of the capillary tube is at a depth of \(8 \mathrm{~cm}\) below the water level. The mouth pressure required to blow an air bubble at the lower end of the capillary will be '\(\mathrm{X}\)' \(\mathrm{cm}\) of water, where \(\mathrm{X}\) is equal to