Two soap bubbles of radii 3 cm and 5 cm are blown at the ends of a tube and the tube is opened so they can communicate. After equilibrium:
ABoth bubbles become equal in size
BSmall bubble shrinks and large bubble grows (because $\Delta P \propto 1/r$, small bubble has higher pressure)
CSmall bubble grows and large shrinks
DNothing happens — bubbles are stable
Answer & Solution
Correct answer: B. Small bubble shrinks and large bubble grows (because $\Delta P \propto 1/r$, small bubble has higher pressure)
Excess pressure $\Delta P = 4T/r$ ⇒ smaller bubble has HIGHER internal pressure. Air flows from high P (small) to low P (large) — small shrinks, large grows. Counter-intuitive but a classic surface-tension result.
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