Question

Figure shows a capillary tube of radius $r$ dipped into water. The atmospheric pressure is $P_0$ and the capillary rise of water is $h$. $s$ is the surface tension for water-glass.


Initially, $h=10\text{cm}$. If the capillary tube is now inclined at ${45}^{\circ }$, the length of water rising in the tube will be

• A. $10\text{cm}$
• B. $10\sqrt{2}\text{cm}$
• C. $\frac{10}{\sqrt{2}}\text{cm}$
• D. None

Answer 1

The correct option is B $10\sqrt{2}\text{cm}$


If number of capillary tubes are in the fluid at different angles then the capillary rise will be the same in all tubes that is independent of angle.
In this case the height of water rise is same but they ask the length of tube upto which water rise.
so,
$l\cos \theta =h$
$l=\frac{h}{\cos 45}$
$l=10\sqrt{2}cm$