Physics Fluid Dynamics PMDC Conceptual Practice
PMDC Verified Question 23 of 37
For an ideal fluid flowing exclusively through a uniform horizontal pipe, how is Bernoulli's equation simplified?
A
\( P + \frac{1}{2}\rho v^2 = \text{constant} \)
B
\( P + \rho g h = \text{constant} \)
C
\( P + \rho v = \text{constant} \)
D
\( 2P + 2\rho v^2 = \text{constant} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( P + \frac{1}{2}\rho v^2 = \text{constant} \)
Concept:

Bernoulli's equation accounts for pressure, kinetic energy, and potential energy per unit volume along a streamline.

Formula:

$$ P + \frac{1}{2}\rho v^2 + \rho g h = \text{constant} $$

Solution:

  • Because the pipe is perfectly horizontal, the elevation height \( h \) remains constant along the flow path.
  • Therefore, the potential energy term \( \rho g h \) does not change and is absorbed into the constant on the right side of the equation.
  • The simplified equation becomes: \( P + \frac{1}{2}\rho v^2 = \text{constant} \).


Why other options are incorrect:

Option B removes the kinetic energy term entirely (used only for static fluids). Option C drops the square on the velocity, violating energy dimensions. Option D applies incorrect arbitrary multipliers.

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