Sentence:  Just as the pressure exerted by surface tension in a spherical drop is * * f and the pressure exerted by surface tension on a cylindrical shape is * * f , the pressure exerted by any curved <WSD>surface</WSD> is * * f , where |g is the interfacial tension and * * f and * * f are the two radii of curvature . 
Meaning of the word marked with <WSD> tags:  the extended two-dimensional outer boundary of a three-dimensional object