Question

A thin liquid film formed between a U-shaped wire and a light slider supports a weight of `1.5xx10^-2N` (see figure). The length of the slider is 30cm and its weight negligible. The surface tension of the liquid film is

A. (a) `0.0125Nm^-1`
B. (b) `0.1Nm^-1`
C. (c) `0.05Nm^-1`
D. (d) `0.025Nm^-1`

Answer 1

Correct Answer - D
At equilibrium,
`2Tl=mg`
`T=(mg)/(2l)=(1.5xx10^-2)/(2xx30xx10^-2)=1.5/60=0.025N//m=0.025Nm`