Length of the slider, \(l=30 cm =0.3 m\)
A soap film has two free surfaces.
\(\therefore\) Total length \(=2 l=2 \times 0.3=0.6 m\)
Surface tension, \(S=\frac{\text { Force o-Weight }}{2 l}\) \(=\frac{1.5 \times 10^{-2}}{0.6}\)\(=2.5 \times 10^{-2} N / m\)
Therefore, the surface tension of the film is \(2.5 \times 10^{-2}\; N m ^{-1}\)
(જો $\mathrm{g}=10 \mathrm{~ms}^{-2}$ હોય).
વિધાન $-2$ : પ્રવાહીનું તાપમાન વધતાં પૃષ્ઠતાણ ઘટે છે.