A rectangular film of liquid is extended from `(4 cm xx 2 cm)` to `(5 cm xx 4 xx cm)`. If the work done is `3 xx 10^(-4)J`, the value of the surface tension of the liquid is

Options

A. `0.2 Nm^(-1)`
B. `8.0 Nm^(-1)`
C. `0.250 Nm^(-1)`
D. `0.125Nm^(-1)`

Answer

D

Explanation

`W=T (2Delta A) {Delta A= (20-8) cm^(2)}`
`rArr T= (W)/(2 Delta A) = (3 xx 10^(-4))/(2 xx 12 xx 10^(-4))= 0.125Nm^(-1)`