Physics Fluid Dynamics PMDC Conceptual Practice
PMDC Verified Question 18 of 37
In fluid mechanics, when a liquid is described strictly as 'incompressible', this indicates that:
A
Its density remains entirely constant.
B
It experiences no internal frictional forces.
C
Its velocity is independent of spatial coordinates.
D
Its mass changes based on the applied pressure.
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Its density remains entirely constant.
Concept:

Compressibility is the measure of a fluid's relative volume change in response to a pressure change.

Formula:

$$ \rho = \frac{m}{V} = \text{constant} $$

Solution:

  • An incompressible fluid cannot change its volume (\( V \)) regardless of how much pressure is applied.
  • Since the mass (\( m \)) is conserved and volume (\( V \)) is fixed, the ratio \( m/V \), which is density, must remain strictly constant.


Why other options are incorrect:

Option B defines a 'non-viscous' fluid. Option C defines 'uniform flow'. Option D violates the law of conservation of mass.

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