Answer: Faster (by continuity equation).
- A Faster (by continuity equation)
- B Slower
- C At the same speed
- D Depends on fluid density
Correct answer: A. Faster (by continuity equation)
Explanation: A<sub>1</sub> v<sub>1</sub> = A<sub>2</sub> v<sub>2</sub>. Smaller cross-section A<sub>2</sub> requires larger velocity v<sub>2</sub> for the same volume flow rate. This is seen in nozzles and hoses.
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.