The surface tension of soap solution is `0.030` N/m . What is the energy needed to increase the radius of a soap bubble from 4 cm to 6 cm ?

Options

A. `1.5 xx10^(3)`J
B. `1.5 xx10^(-2)`J
C. `3xx10^(-2)`J
D. `1.5 xx10^(-4)`J

Answer

A

Explanation

`W = 2 xx T xx[ 4piR_(2)^(2)-4piR_(1)^(2)]`
`=8piT[R_(2)^(2)-R_(2)^(2)]`
`= 8 xx 3.14 xx 30 xx 10^(-3) [(36 -16)xx10^(-4)]`
` = 240 xx 3.14 xx20 xx10^(-7)`
` divide 150 xx 10^(-5) = 1.5 xx10^(-3)`J