The surface tension of a liquid is ` 5 N m ^ ( -1 ) ` If a film is held on a ring of area ` 0.02 m ^ 2 `, its total surface energy is about x Joules. Find x.

Options

A. `5 xx 10^(-2) J`
B. `2.5 xx 10^(-2) J`
C. `2 xx 10^(-1) J`
D. `3 xx 10^(-1) J`

Answer

C

Explanation

We know that surfaces energy
`U_(s) = T xx Area`.
Hence. As `2` films are formed because of ring. So
`U_(s) = T xx 2 xx (A)`
`= 5 (N)/(m) xx 2 xx 0.02 m^(2) = 0.2 J`