Question

What is the value of pressure inside the bubble of radius 1cm, if the bubble is in water at a depth (H) of 1m? Assume atmospheric pressure to be 1atm, surface tension = 0.075N/m & density of water = 1000kg/m^3.

(a) 110015 Pa

(b) 109985 Pa

(c) 26 atm

(d) 4 atm

This question was addressed to me in semester exam.

My doubt stems from Fluids Mechanical Properties in portion Mechanical Properties of Fluids of Physics – Class 11

Answer 1

Correct answer is (a) 110015 Pa

The explanation: The pressure in the bubble will be more than the pressure just outside it by an amount 2S/R.

The pressure just outside the bubble is P0 + ρgh.

Therefore, pressure inside bubble = P0 + ρgh + 2S/R

= 10^5 + (1000*10*1) + (2*0.075/0.01)

= 110015 Pa.