Question

A liquid is contained in a vertical tube of semicircular cross section. The contact angle is zero. The forces of surface tension on the curved part and on the flat part are in ratio.

• A. 1:1
• B. 1:2
• C. π:2
• D. 2:π

Answer 1

The correct option is C

π:2

The surface is in contact with curved and the flat part.Here is the top view of the container,

Arrow represents the way surface is trying to pull the contact part of container.
Let $F_1$ = Force due to surface tension on the curved part
Let S = surface tension of the liquid
r = radius of semicircular part
$\Rightarrow F_1=S\left\{\pi r\right\}$
$F_2$ = Force due to surface tension on the flat part
$F_2=S\times 2r$
$\Rightarrow \frac{F_1}{F_2}=\frac{S\pi r}{S2r}=\frac{\pi }{2}$
Hence (c)