An incompressible fluid flows through a pipe that becomes narrower in one section. The fluid speed increases in that region to maintain:
Correct answer: C. Constant mass flow rate
- A. Constant pressure
- B. Constant energy
- C. Constant mass flow rate
- D. Constant volume
Explanation
The same mass must pass every cross section each second, so where the area falls the speed must rise in proportion, which is the equation of continuity and is simply conservation of mass applied to a fluid. Pressure certainly does not stay constant; it falls in the constriction, which is Bernoulli's principle. This is why a thumb over a hose makes the water squirt further.
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About Equation of Continuity
The equation of continuity expresses conservation of mass in fluid flow. For steady incompressible flow, Av remains constant, so fluid speed increases when the cross-sectional area decreases; for compressible flow, ρAv is constant. This relation describes flow rate and area-speed changes without including pressure effects from Bernoulli’s equation.
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