The velocity of water in a rier is `18kmh^-1` near the surface. If the river is 5 m deepm, find the shearing stress between the horizontal lyers of water. The coefficient of viscosity of water `=10^-2 poise.

Explanation

As velocity at the bottom of the river will be zero,
Velocity gradient `(dv)/(dy)=(18xx10^(3))/(60xx60xx5)=1s^(-1)`
Shear stress `=F/A= eta (dv)/(dy)=10^(-3)xx1=1xx10^(-3)N//m^(2)`