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PART - 2 CH - 9 Mechanical Properties of Fluids — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsPART - 2 CH - 9 Mechanical Properties of Fluids2 Marks
Question
Define critical velocity.
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Answer

Critical velocity : The critical velocity is that maximum velocity of the flow of a fluid, at a velocity below which the flow of fluid is streamline and at a velocity above which the flow of fluid is trubulent.
Critical velocity is directly proportion to coefficient of viscosity $\eta$ of fluid and it is inversely proportional to the density of liquid ( $\rho$ ) and inversely proportional to the diameter of tube (D).
Therefore, $v _{ C } \propto \frac{\eta}{\rho D }$
$\therefore\quad v _{ C }=\frac{ R \eta}{\rho D }$
where $R \approx 2000$ is Reynolds number.

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