The Total solution for NCERT class 6-12
A U-shaped wire is dipped in a soap solution, and removed. Thethin soap film formed between the wire and the light slider supports a weightof 1.5 × 10–2 N (which includes the small weight of theslider). The length of the slider is 30 cm. What is the surface tension of thefilm?
The weight that the soap film supports, W = 1.5 ×10–2 N
Length of the slider, l = 30 cm = 0.3 m
A soap film has two free surfaces.
∴Totallength = 2l = 2 × 0.3 = 0.6 m
Surface tension,
=
Therefore, the surface tension of the film is 2.5 × 10–2 Nm–1.