Question

The velocity of upper layer of water in a river is $36\ kmh^{–1}$. Shearing stress between horizontal layers of water is $10^{–3} Nm^{–2}$. Depth of the river is ______ m. (Co-efficient of viscosity of water is $10^{–2} Pa.s$)

Answer 1

We know that,
$F = -ηA\frac {du}{dx}$

$10^{-3} = 10^{-2} \times \frac {10}{h}$

$h =\frac {10^{-1}}{10^{-3}}$
$h = 100\ m$

So, the answer is $100 \ m$.