Question

the excess pressure inside an air bubble of radius r just below the surface of the water is p. the excess pressure inside a drop of the same radius just outside the surface is p2. if t is surface tension, then how is p=p2?

Answer 1

because excess pressure inside an air bubble just below =2T/R and excess pressure of drop just outside = 2T/R

Answer 2

Pressure inside and outside the bubble is equal:

Explanation:

• A bubble is made of very thin spherical layer.
• A stable bubble requires a pressure balance between inside and outside the bubble.
• The pressure inside the bubble is need to be higher than pressure outside the bubble to keep a bubble stable.
• Here, half the bubble is inside the water and another half is outside the water. But the pressure inside the bubble balances out the pressure outside the bubble.
• Excess pressure inside an air bubble below surface is given by the formula:

P = 2T/r

• Excess pressure inside an air bubble above surface is given by the formula:

P1 = 2T/r

• Therefore,

P = P1