Question

Water flows at a speed of $16\text{cm/s}$ through a tube of radius $10\text{cm}$. Co-efficient of viscocity of water at room temperature is $0.01$ poise. Then, find the Reynolds number.

• A. $3000$
• B. $2800$
• C. $3200$
• D. $3400$

Answer 1

The correct option is C $3200$

Given, speed of water, $\left(v\right)=16\text{cm/s}=16\times {10}^{-2}\text{m/s}$
Co-efficient of viscocity of water, $\eta =0.01\text{poise}$
Radius of tube, $\left(r\right)=10\text{cm}$
$\therefore$ Diameter of tube, $\left(D\right)=2r=20\text{cm}=20\times {10}^{-2}\text{m/s}$
Density of water, $\rho =1000{\text{kg/m}}^3$
We know from the definition of
Reynolds number, $\left(R\right)=\frac{\rho vD}{\eta }$
$=\frac{1000\times 16\times {10}^{-2}\times 20\times {10}^{-2}}{0.01}$
$\Rightarrow R=3200$
Hence, option (c) is the correct answer.