Question

An incompressible fluid is flowing in a cylindrical pipe of internal diameter $4cm$ with a velocity of $5m/s$. If this tube is joined with another tube of internal diameter $2cm$, then the velocity of flow of fluid in the smaller tube will be

• A. $10m/s$
• B. $20m/s$
• C. $40m/s$
• D. $5m/s$

Answer 1

The correct option is B $20m/s$

According to equation of continuity for incompressible fluid
$A_1{V}_1=A_2{V}_2$
Thus ${R_1}^2{V}_1={R_2}^2{V}_2$ $(Area=\pi R^2)$
$\frac{2^2}{{100}^2}\times 5=\frac{1^2}{{100}^2}\times V_2$
$V_2=20m/s$