Question

A disc of paper of radius R has a hole of radius r. It is floating on a liquid of surface tension T then the force acting on the disc is

Answer 1

$F=T\times 2\pi r$

$F^{\prime }=T\times 2\pi \left(r/2\right)$

$F_{net}=T\left(3\pi r\right)=\frac{3}{2}(T\times 2\pi r)$

$=\frac{3}{2}{F}^{\prime }$