Q. Water in river 20 m deep is flowing at a speed of $10\ {ms}^{- 1}$. The shearing stress between the horizontal layers of water in the river in ${N\ m}^{- 2}$ is (coefficient of viscosity of water$= 10^{- 3}$ SI units)
A) $1 \times 10^{- 2}\ {Nm}^{- 2}$
B) $0.5 \times 10^{- 2}\ {Nm}^{- 2}$
C) $1 \times 10^{- 3}\ {Nm}^{- 2}$
D) $0.5 \times 10^{- 3}\ {Nm}^{- 2}$
Explanation
(d) $Shearing\ stress = ɳ\left( \frac{dv}{dx} \right)$
= $10^{- 3}\left( \frac{10}{20} \right) = 0.5 \times 10^{- 3}{Nm}^{- 2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.