Question

The adjoining diagram shows three soap bubbles $A$ , $B$ and $C$ prepared by blowing the capillary tube fitted with stop cocks, $S_1$ , $S_2$ and $S_3$ . The bubble $B$ is the largest and the bubble $C$ is the smallest. With stop cock $S$ closed, what will happen when we open the stop cocks $S_1$ , $S_2$ and $S_3$ simultaneously?

• A. $B$ will start collapsing with volumes of $A$ and $C$ increasing
• B. $C$ will start collapsing with volumes of $A$ and $B$ increasing
• C. $C$ and $A$ both will start collapsing with the volume of $B$ increasing
• D. Volumes of $A$ , $B$ and $C$ will become equal at equilibrium

Answer 1

Answer: (C)

Excess pressure inside soap bubble is inversely proportional to the radius of bubble i.e. $\Delta P\propto \frac{1}{r}$
This means that bubbles $A$ and $C$ posses greater pressure inside it than $B$ . So the air will move from $A$ and $C$ towards $B$ .