A thin disc of radius `R`, just touching the liquid surface forms one arm of a balance. The palte is balanced by some weight on the other side of the balance. How much extra weight should be added on the other side, so that the disc can just come cut of water ?

Explanation

Surface tension force on the disc is `(T)(2piR)`
For balance `(T)(2piR) = (Deltam)g rArr Deltam = ((T)(2piR))/(g)`