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Most of the people touch their tongues with fingers and then turn pages. Why do pages don't turn sometimes with dry hands? And what happens when we turn them with wet hands? If water decreases the friction between pages, why do wet pages stick together?

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  • $\begingroup$ Adhesion versus cohesion $\endgroup$ – user167453 Oct 9 '17 at 13:19
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The direct answer is that when a wet hand is used to turn pages, the adhesive force comes into picture. When the hand is wet, there exist adhesive force (attraction between unlike molecules) between water molecules and hand, as well as water molecules and paper. What makes water molecules stay together is the cohesive force (which is the surface tension) which adds up the easiness to turn paper. If hand alone is used, the adhesion is weaker.

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