The Laplace formula is a result in fluid mechanics that gives the surface pressure between two continuous media. The surface of separation is really a transitional layer, but it is so thin that in classical mechanics it can be considered a dividing surface between the two media.
Consider two continuous media (top and bottom) whose surface of separation undergoes a small displacement. If and are the principal radii of curvature of the surface in some sample region, then the difference of pressures is
where is the surface tension coefficient.
- Landau, L.D. and Lifschitz, E.M. Fluid Mechanics. Oxford : Butterworth-Heinemann, 1987.
- "Film notes for surface tension in fluid mechanics" (PDF). Trefethen, Encyclopedia Britannica. 1969. Retrieved 2014-03-25.