Two soap bubbles are blown from the same soap solution ( N m ) on the two ends of a…
PHYSICS · Subjective · Fermi University Physics · Fluids & Continuum Physics · Fluid statics and the continuum picture · Fluid statics and the continuum picture
Fluids and Continuum Physics, Ch Surface tension, capillarity and wetting
Problem
Two soap bubbles are blown from the same soap solution (γ=0.025 N m−1) on the two ends of a short tube fitted with a closed tap in the middle. One bubble has radius 1.0 cm, the other 3.0 cm. Both bubbles are surrounded by air at atmospheric pressure, and each film has two faces. The tap is now opened, so that air can pass between the two bubbles and nowhere else. Evaporation and any flow resistance in the tube are ignored. Which one of the following happens? (a) Air flows from the large bubble into the small one, until the two radii are equal. (b) Air flows from the small bubble into the large one, so the small bubble shrinks further and the large one grows. (c) No air flows, because the gauge pressure inside a soap bubble does not depend on its radius. (d) Air flows from the large bubble into the small one until the small bubble bursts.