A U-shaped wire is dipped in a soap solution, and removed. The thin soap film formed between the wire and the light slider supports a weight of 1.5 × 10–2 N (which includes the small weight of the slider). The length of the slider is 30 cm. What is the surface tension of the film ?
Weight mg=1.5×10−2N Length of slider l=30×10−2m Force due to surface tension = weight We know that σ×2l=mg Therefore surface tension σ=2lmg =2×30×10−21.5×10−2 =2.5×10−2 Nm−1.
