Question
The velocity of water in a river is 18 km/hr at the surface. If the river is 5 m deep, find the shearing stress between the horizontal layers of water. The viscosity of water is 10^{–3} poiseuille.

None of these



easy
Solution
As velocity at the bottom of the river will be zero, velocity gradient
Now as the viscous force is tangential to the area,
Shear stress,
.
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