Answer: Force per unit length along the surface.
- A Force per unit length along the surface
- B Force per unit area
- C Energy per unit volume
- D Pressure difference across a surface
Correct answer: A. Force per unit length along the surface
Explanation: Surface tension T = F/L (force per unit length, or equivalently, energy per unit area). It acts along the surface of a liquid, minimizing surface area.
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.