A thin liquid film formed between a U-shaped wire and a light slider supports a weight of `1.5 xx 10^(-2)` N (see figure). The length of the slider is 30 cm and its weight negligible. The surface tension of the liquied film is

Options

A. `0.0125 N m ^(-1) `
B. ` 0.1 Nm ^(-1) `
C. ` 0.05 N m ^(-1) `
D. ` 0.025 N m ^ ( -1) `

Answer

D

Explanation

The force due to the surface tension will balance the weight.
`F=W" "Rightarrow" "2TL=W" "or" "T=(W)/(2L)`
Substituting the given values, we get
`T=(1.5xx10^(-2)N)/(2xx30xx10^(-2)m)=0.025Nm^(-1)`