question_answer

In a laminar boundary layer over a flat plate, what would be the ratio of wall shear stresses \[{{\tau }_{1}}\] and \[{{\tau }_{2}}\] at the two sections which lie at distances \[{{x}_{1}}=30\,\,cm\] and \[{{x}_{2}}=90\,\,cm\] from the leading edge of the plate?

A) \[\frac{{{\tau }_{1}}}{{{\tau }_{2}}}=3.0\]                  

B) \[\frac{{{\tau }_{1}}}{{{\tau }_{2}}}=\frac{1}{3}\]

C) \[\frac{{{\tau }_{1}}}{{{\tau }_{2}}}=\,\,{{\left( 3.0 \right)}^{1/2}}\]               

D) \[\frac{{{\tau }_{1}}}{{{\tau }_{2}}}=\,\,\left( 3.0 \right)\]