Physics Fluid Dynamics PMDC Conceptual Practice
PMDC Verified Question 5 of 37
In the study of fluid dynamics, a fluid is considered to be undergoing 'incompressible flow' if:
A
Its velocity at a given point cannot change with time.
B
Its density remains perfectly constant regardless of time or location.
C
Its pressure at a given point remains unchanged.
D
There are no internal frictional forces present.
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Its density remains perfectly constant regardless of time or location.
Concept:

Incompressibility is a material property defining how density responds to changes in pressure.

Formula:

$$ \rho = \text{constant} $$

Solution:

  • When a fluid is incompressible, it cannot be squeezed into a smaller volume.
  • This physically means the density (mass per unit volume) does not change under pressure variations.
  • Hence, the density remains constant with time and location throughout the flow field.


Why other options are incorrect:

Option A describes steady flow, not incompressible flow. Option C is incorrect because pressure inherently changes in flow fields (e.g., Bernoulli). Option D describes a non-viscous (ideal) fluid.

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