Answer: Smaller bubble (r 2 ) shrinks and larger (r 1 ) grows.
- A Smaller bubble (r<sub>2</sub>) shrinks and larger (r<sub>1</sub>) grows
- B The larger bubble shrinks while the smaller one grows instead
- C Both bubbles settle to exactly the same final equilibrium radius
- D Neither bubble's size changes once they are connected by the tube
Correct answer: A. Smaller bubble (r<sub>2</sub>) shrinks and larger (r<sub>1</sub>) grows
Explanation: Excess pressure in a soap bubble = 4T/r. The smaller bubble (r<sub>2</sub>) has higher pressure than the larger one (r<sub>1</sub>). Air flows from smaller to larger. The smaller bubble shrinks.
Since the same volume of fluid must pass every cross-section per second (continuity), the fluid speeds up where the pipe narrows; Bernoulli's equation then says this faster-moving fluid has lower pressure - the principle behind a venturi meter and an aircraft wing's lift.
Concept context
Pressure, buoyancy, Bernoulli equation, viscosity, and surface tension.