Question

A flat plate of 0.15 $m^2$ is pulled at 20 cm/s relative to another plate, fixed at a distance of 0.02 cm from it with a fluid having $\mu$ = 0.0014 N-s/$m^2$ separating them. What is the power required to maintain the motion?

• A. 0.014 W
• B. 0.021 W
• C. 0.035 W
• D. 0.042 W

Answer 1

The correct option is D 0.042 W

$Force,F=\mu \frac{du}{dy}\times A=0.0014\times \frac{0.2}{0.02\times {10}^{-2}}\times 0.15=0.21NPowerrequired=F\times v=0.21\times 0.2=0.042W$