Answer: h = P atm /(ρg) ≈ 10.3 m for water.
- A h = P<sub>atm</sub>/(ρg) ≈ 10.3 m for water
- B h = ∞, since a siphon can theoretically rise to any height
- C h = 5 m, a fixed value independent of atmospheric pressure
- D h = 1 m, a fixed value independent of fluid density or pressure
Correct answer: A. h = P<sub>atm</sub>/(ρg) ≈ 10.3 m for water
Explanation: The siphon works as long as pressure at the top does not go below zero (vacuum). Maximum height: P<sub>atm</sub> - ρgh = 0 → h = P<sub>atm</sub>/(ρg) = 10⁵/(1000×10) = 10 m for water.
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.