Answer: 8 m/s.
- A 4 m/s
- B 8 m/s
- C 6 m/s
- D 12 m/s
Correct answer: B. 8 m/s
Explanation: By continuity A<sub>1</sub>v<sub>1</sub> = A<sub>2</sub>v<sub>2</sub>: v<sub>2</sub> = 6 × 2/1.5 = 8 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.