Question

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 x 10-2 N (which includes the small weight
of the silder). The length of the silder is 30 cm.
What is the surface tension of the film ?​

Answer 1

Answer:

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.

∴ Total length = 2l = 2 × 0.3 = 0.6 m

Surface tension, S = Force or Weight / 2l

= 1.5 × 10-2 / 0.6

= 2.5 × 10-2 N/m

Therefore, the surface tension of the film is 2.5 × 10–2 N m–1.

Answer 2

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