Answer: 288 Pa.
- A 576 Pa
- B 144 Pa
- C 72 Pa
- D 288 Pa
Correct answer: D. 288 Pa
Explanation: A liquid drop has one surface, so ΔP = 2T/r = 2 × 0.072/(5 × 10<sup>-4</sup>) = 288 Pa.
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.