A liquid having coefficient of viscosity $0.02$ decapoise is filled in a container of cross-sectional area $20 \,m ^2$. If viscous drag between two adjacent layers in flowing is $1 \,N$, then velocity gradient is ........ $s ^{-1}$
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(b)
Given,
$F=1\,N$
$\eta=0.02 \text { decapoise }=0.02\,N / sm ^2$
$A=20\,m ^2$
The drag force is given by
$F =\eta A \frac{ dv }{ dx }$
$\frac{ dv }{ dx }=\frac{ F }{\eta A }=\frac{1}{0.02 \times 20}$
velocity gradient, $\frac{ dv }{ dx }=2.5\,s ^{-1}$
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