Water flows through a horizontal pipe of non-uniform cross-section. At a constriction where the pipe narrows and fluid velocity increases, what happens to the internal fluid pressure according to Bernoulli's principle?

Answer and explanation

Correct answer: C. the fluid pressure decreases as kinetic energy density increases

  1. Step 1: Bernoulli's principle for horizontal streamline flow states P + 0.5 ρ v² = constant. Step 2. Where cross-section narrows, flow velocity v increases by continuity. Step 3. An increase in dynamic pressure (0.5 ρ v²) requires a corresponding decrease in static pressure P. Answer: the fluid pressure decreases as kinetic energy density increases. Why not the others: Pressure drops rather than rises; pressure changes with velocity; temperature does not drop to absolute zero.

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