JEE Mains · Physics · STD 11 - Fluid mechanics
- JEE Mains 2015
- Hard
- MCQ
If it takes \(5\,minutes\) to fill a \(15\,litre\) bucket from a water tap of diameter \(\frac{2}{{\sqrt \pi }}cm\) then the Reynolds number for the flow is (density of water \(= 10^3\,kg/m^3\) ) and viscosity of water \(= 10^{-3}\,Pa.s\) ) close to
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(5500\)
Step-by-step Solution
Detailed explanation
Given: Diameter of water tap \( = \frac{2}{{\sqrt \pi }}\,cm\)
\(\therefore \,\,Radius,\,r = \frac{1}{{\sqrt \pi }} \times {10^{ - 2}}\,m\)
\(\frac{{dm}}{{dt}} = \rho AV\)
\(\frac{{15}}{{5 \times 60}} = {10^3} \times \pi {\left( {\frac{1}{{\sqrt \pi }}} \right)^2} \times {10^{ - 4}}V\)
\( \Rightarrow V = 0.05\,m/s\)
Reynold's number, \({R_e} = \frac{{\rho Vr}}{n}\)
\( = \frac{{{{10}^3} \times 0.5 \times \frac{2}{{\sqrt \pi }}{{10}^{ - 2}}}}{{{{10}^{ - 3}}}} \cong 5500\)
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