Answer: 2h.
- A h/2
- B h
- C 2h
- D 4h
Correct answer: C. 2h
Explanation: Capillary rise h = 2T cosθ/(ρgr), so h ∝ 1/r; halving r doubles the rise to 2h.
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.