Answer: 4 m/s.
- A 4 m/s
- B 0.25 m/s
- C 2 m/s
- D 1 m/s
Correct answer: A. 4 m/s
Explanation: A<sub>1</sub> v<sub>1</sub> = A<sub>2</sub> v<sub>2</sub>. A ∝ d². (4²)(1) = (2²)(v<sub>2</sub>). 16 = 4 v<sub>2</sub>. v<sub>2</sub> = 4 m/s.
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.