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A U shaped wire is dipped in soap solution and removed. The thin soap film formed between the wire and the light slider supports a weight of #1.5 xx 10^(-2) N# {including the weight of the slider}. The length of the slider is 30 cm. Find the surface tension of the soap solution?

1 Answer
A08
Mar 7, 2018

Surface tension #gamma# of a liquid is the force per unit length.

The soap film formed on the U shaped wire has two sides, each of which contributes equally to the force.

Total weight supported by the soap film#=1.5xx10^-2\ N#
The length of the slider is #=30/100=0.3\ m#
Total force due to surface tension #=2xx"length"xxgamma=0.6gamma#

Equating the two we get

#0.6gamma=1.5xx10^-2#
#=>gamma=(1.5xx10^-2)/0.6=2.5xx10^-2\ Nm^-1#

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