Question

Two capillary tubes A and B are immersed in water. One is straight and the other is in the form of a rectangular U-tube as shown in the figure. The tube A is sufficiently long. The lower end of the bent tube is at depth $H$. Then, there will be no flow of water from tube B if

• A. $H=h$
• B. $0<h<H$
• C. $H=0$
• D. all of the above

Answer 1

The correct option is D all of the above

Pressure at the point in the tube parallel to the surface of water will be $P_o+\rho gh$

Applying Bernoulli's law at points in bent tube i.e at surface of water and exit of tube

$P_o+\rho gh=P_o-\rho gH+\frac{1}{2}\rho {v_c}^2$

Velocity at point C is given by, $V_c=\sqrt{2g(H-h)}$

Hence $V_c$ is real for $H\ge h$