A U-shaped wire is dipped in a soap solution, and removed. A thin soap film formed between the wire and a light slider supports a weight of `1.5xx10^(-2)N` (which includes the small weigh of the slider). The length of the slider is 30cm. What is the surface tension of the film?

Explanation

In present case force of surface tension is balancing the weight of `1.5xx10^(-2)N` hence force of surface tension `F=1.5xx10^(-2)N`
Total length of liquid film `l=2xx30cm=60cm=0.6m` because the liquid film has two surfaces.
surface tension `T=F//l=1.5xx10^(-2)N//0.6m=2.5xx10^(-2)Nm^(-1)`