Monday, January 26, 2015

fluid dynamics - What causes surface tension actually?



Surface tension has really made me crazy!


Surface tension occurs at the interface of air & water. It is a force per unit length tangential to the intersurface.


But what actually causes it?


One explanation is that there are very less no. of molecules on the interface, remaining far away from each other. Due to this, greater attractive force does exist which causes surface tension. Now, the question is why the density is low.


Another explanation that my book also vaguely offers is the asymmetric downward force on the water interface. But question evidently arise, if the force is downward, how can it produce a tangential surface tension??



Now, what should be the answer to these mind-chocking questions? And are these explanations linked with each other( which I greatly believe)??




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