Question

The velocity of water in river is 8 km/hr of the upper surface. The river is 12 m deep. If the coefficient of viscosity of water is 10^-2 poise then the shearing stress between horizontal layers of water is ______.

Options

• 0.25 x 10^-2 N/m²

• 1.85 x 10^-3 N/m²

• 1.5 x 10^-3 N/m²

• 0.75 x 10^-3 N/m²

Answer 1

The velocity of water in river is 8 km/hr of the upper surface. The river is 12 m deep. If the coefficient of viscosity of water is 10^-2 poise then the shearing stress between horizontal layers of water is 1.85 x 10^-3 N/m².

Explanation:

F = ` eta  "A" "dv"/"dx"`

`therefore "shearing stress" = "F"/"A" = eta  "dv"/"dx"`

`therefore "shearing stress" = 10^-2 xx (8 xx 5/18)/12`

= 1.85 x 10^-3 N/m²