Eduprobe
Question:
The velocity of water in a river is 18 km/hr near the surface. If the river is 5 m deep, find the shearing stress between the horizontal layers of water. The coefficient of viscosity of water = 10⁻⁶ poise.
10⁻⁷ N/m²
10⁻⁸ N/m²
10⁻⁶ N/m²
10⁻⁵ N/m²
Solution:
Velocity of a layer of water, V = (18 * 1000) / (60 * 60) = 5 m/s
Also, η = 10⁻⁶ poise = 10⁻⁷ Ns/m²
Shear stress, τ = η(dV/dy) = η(V/d) = 10⁻⁷ * 5 / 5 = 10⁻⁷ N/m²