Question

A river $10m$ deep is flowing at $5m/s$. The shearing stress between horizontal layers of the river is $(\eta ={10}^{-3}SIunits)$.

• A. ${10}^{-3}N/m^2$
• B. $0.8\times {10}^{-3}N/m^2$
• C. $0.5\times {10}^{-3}N/m^2$
• D. $1N/m^2$

Answer 1

Answer: (C)

$0.5\times {10}^{-3}N/m^2$

Shearing stress $=\frac{|viscousforce|}{area}$
$=\frac{\eta A\frac{dv}{dx}}{A}=\eta \frac{dv}{dx}$
$={10}^{-3}\times \frac{5}{10}N/m^2=0.5\times {10}^{-3}N/m^2$.