Question

Two water pipes of diameters 2 cm and 4 cm are connected with the main supply line. The velocity of flow of water in the pipe of 2 cm diameter is

• A. 4 times that in the other pipe
• B. 1/4 times that in the other pipe
• C. 2 times that in the other pipe
• D. 1/2 times that in the other pipe

Answer 1

The correct option is A

4 times that in the other pipe

$d_A=2cm$ and $d_B=4cm$$\therefore r_A=1cm$ and $r_B=2cm$

From equation of continuity, av = constant

$\therefore \frac{v_A}{v_B}=\frac{a_B}{a_A}=\frac{\pi (r_B{)}^2}{\pi (r_A{)}^2}=⟮\frac{2}{1}{⟯}^2\Rightarrow v_A=4v_B$