The surface tension of a liquid is `5` Newton per metre. If a film is held on a ring of area `0.02 metres^(2)`, its surface energy is about :

Options

A. `10^(-1)`J
B. `2.5 xx10^(2)`J
C. `20 xx 10^(-2)`J
D. `3 xx 10^(-1)`J

Answer

C

Explanation

Surface energy ` = S.T xx "area"`
` = T xx 2A`
` = 5 xx 2 xx 0.02 = 0.2 ` J