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.

Options

A. `10^(-1) N//m^(2)`
B. `10^(-2) N//m^(2)`
C. `10^(-3)N//m^(2)`
D. `10^(-4) N//m^(2)`

Answer

B

Explanation

`eta=10^(-2)` poise, v=18 km/h =5m/s, l=5m
Velocity gradient `=v/l=5/5 =1s^(-1)`
Coefficient of viscosity, `eta=("shearing stress")/("velocity gradient")`
Shearing stress `=eta xx " velocity gradient"`
`=10^(-2) xx 1=10^(-2)Nm^(-2)`