A wire is bent in the form of a `U`-shape and a slider of negligible mass is connecting the two vertical sides of the U-shape. This arrangement is dipped in a soap solution and lifted a thin soap film is formed in t he frame it supports a weight of `2.0xx10^(-2) N` if the length of the slider is 40 cm what is the surface tension of the film?

Explanation

`W=2.0xx10^(-2)N" "l=40cm=0.4m`
Upward force due to surface tension `=Txx2l`
In equilibrium, `W=Txx2l`
`T=(W)/(2l)=(2xx10^(-2))/(2xx0.4)=2.5xx10^(-2)Nm^(-1)`,