A drop of Volume `V` is pressed between the two glass plates so as to spread to an area of `A`. If `T` is the surface tension, the normal force required to separate the glass plates is

Options

A. `sqrt((sigma)/(g(2rho-d)))`
B. `sqrt((2sigma)/(g(2rho-d)))`
C. `sqrt((6sigma)/(g(2rho-d)))`
D. `sqrt((12sigma)/(g(2rho-d)))`

Answer

D

Explanation

`2pirsigma+(1)/(2)xx(4)/(3)pir^(3)dg=(4)/(3)pir^(3)rhog`
or `2pirsigma=(pir^(2)g)/(3)[4rho-2d]` or `r^(2)=(3xx2pisigma)/(g(2rho-2d))`
or `r^(2)=(3sigma)/(g(2rho-d))` or `r=sqrt((3sigma)/(g(2rho-d)))`
Diamter `=2r=sqrt((12sigma)/(g(2rho-d)))`