Question

What will be critical velocity of water in a tube of radius $1m$, if the coefficient of viscosity of water is $1793$ poise and Reynold's number is $1000$.

• A. $17.93cm/s$
• B. $17.93\times {10}^{2}cm/s$
• C. $17.93\times {10}^{4}cm/s$
• D. $17.93\times {10}^{3}cm/s$

Answer 1

The correct option is D $17.93\times {10}^{3}cm/s$

$V_c=\frac{\mu N_r}{\rho R}Given\mu =1793poise=179.3N.s{m}^{-2},N_r=1000\rho =1000kg{m}^{-3},R=1m{V}_c=\frac{179.3\times 1000}{1000\times 1}\left(\frac{kgm{s}^{-2}\times s{m}^{-2}}{kg{m}^{-3}\times m}\right)V_c=179.3m{s}^{-1}{V}_c=17.9\times {10}^{-3}cm{s}^{-1}$