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Let σ be the surface tension ......

I got to know that the excess pressure for a liquid-gas interface with radii of curvature (see http://en.wikipedia.org/wiki/Surface_tension#Surface_curvature_and_pressure .....the part on Surface curvature and pressure and Young-Laplace equation).

is given by ΔP= σ(1/R1 + 1/R2)

I have 3 cases as shown in my attached figure... in there cases,

I'm guessing that

Please help!!

I got to know that the excess pressure for a liquid-gas interface with radii of curvature (see http://en.wikipedia.org/wiki/Surface_tension#Surface_curvature_and_pressure .....the part on Surface curvature and pressure and Young-Laplace equation).

is given by ΔP= σ(1/R1 + 1/R2)

I have 3 cases as shown in my attached figure... in there cases,

**how do we know which radii/lengths to plug into the above formula?**

*how do we/on what basis do we make the selection..?*I'm guessing that

**we just look at the liquid-gas interface and see what radii are on the opposite sides....but that doesn't work for the**

also, especially in regard to the liquid droplet, if we take the inner radius to be one radius, on the other side of the boundary of the droplet,*rectangular plate*....*we have an infinite radius*!!Please help!!