Answer: Mass (for incompressible fluid).
- A Mass (for incompressible fluid)
- B Kinetic plus potential energy along the streamline
- C Linear momentum of the fluid element
- D Static pressure across the pipe cross-section
Correct answer: A. Mass (for incompressible fluid)
Explanation: The continuity equation follows from conservation of mass for incompressible (constant density) fluids. The volume flow rate Q = Av must be the same everywhere in a pipe.
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.