A cubical block of side ‘a’ and density ‘ ρ ’ slides over a fixed inclined

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9-1.Fluid Mechanics

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A cubical block of side $‘a’$ and density ‘$\rho $’ slides over a fixed inclined plane with constant velocity $‘v’$. There is a thin film of viscous fluid of thickness $‘t’$ between the plane and the block. Then the coefficient of viscosity of the thin film will be

A

$\frac{{3\rho agt}}{{5v}}$

B

$\frac{{4\rho agt}}{{5v}}$

C

$\frac{{\rho agt}}{{v}}$

D

none of these

Solution

For constant velocity, viscous force $=\mathrm{mg} \sin \mathrm{g} \theta$

$\sigma a^{2} \frac{V}{t}=\rho a^{3} g\left(\frac{3}{5}\right)$

$\sigma=\frac{3 \rho a g t}{5 v}$

Standard 11

Physics

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