Question

the ring radius 1 m is lying on the surface of liquid. It is lifted the liquid surface by a force of 4 Newtons in such a way that the liquid fifrn in it remains. intact . The surface tension of liquid will be:-

• A. $\frac{2}{\pi }N/m$
• B. $\frac{1}{\pi }N/m$
• C. $\frac{1}{2\pi }N/m$
• D. $\frac{1}{4\pi }N/m$

Answer 1

The correct option is A $\frac{2}{\pi }N/m$

The loop has a circumference $C=2\pi R$ along which surface tension works, applies force of:

$F=TL=2\pi T$ This force is counteracted by external force of $=4N$ hence

$2\pi T=4\Rightarrow$ $T=\frac{2}{\pi }N/m$