Physics 1029A/B Lecture Notes - Lecture 4: Net Force, High High
15 Feb 2016
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Document Summary
Surface energy (esurface) is a fluid property associated with the presence of a surface towards air. The symmetrical interactions of molecules with their intermediate neighbouring molecules is broken. Sufficiently below the surface, each water molecule has attractive interactions in all directions with nearby neighbors. The attractive forces cancel each other out and thus the molecule is in eq. = e/ a o: where e is the energy needed to increase the surface of a fluid by an area a. Therefore, is the energy (in j) required to form 1m2 of new surface. Another way of looking at is using work (w). W= e= a , where w is the work required to increase the surface by a. If we increase an area a from a= lxly to a=lx(ly+ ly) then the work done to enlarge it is equal to w=f ly. Putting it back in the work formula yields: = a = lx ly=w=f ly and eventually = f/lx.
