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
Diffcult
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$F=\eta A\left(\frac{\Delta V}{\Delta x}\right) ; F=\operatorname{mg} \sin \theta$
$\eta=\frac{F}{A \cdot\left(\frac{\Delta V}{\Delta x}\right)}$
$\eta=\frac{\rho a^{3} \cdot g \sin \theta}{a^{2} v / t}$
$\eta=\frac{\rho a \operatorname{tg} \sin \theta}{v}$
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