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I'm currently taking a physics class, and my teacher explained that friction is the result of intermolecular interactions, and that energy must be applied in order to break these bonds.

This got be thinking about what kinds of things have a high coefficient of friction, and immediately my mind went to sandpaper. The atomic surface of these mineral crystals would be really smooth and not easily polarizable, as they are held tightly in place by the other ions. So does surface area have more to do with friction than actual Van der Waals forces? This would also seem to explain how geckos are so adept and clinging to things like glass, as the tips of their fingers are so highly ridged.

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    $\begingroup$ There are interactions other than van der Waal's forces, so in general, no. $\endgroup$ – Jon Custer Mar 2 '16 at 23:51
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    $\begingroup$ Most of the forces that you encounter day-to-day (apart from gravity) are Coulombic repulsions of outer-shell electrons on the surfaces of macroscopic objects (walls, floors, balls, keyboards, etc.) While you are right about the stickiness of gecko feet being attributable to VDW, the friction from sandpaper is most likely due to its uneven surface which makes it prone to scrape against other surfaces via Coulomb. One might compare this kind of process to sliding strips of velcro against each other. $\endgroup$ – colnegn Mar 4 '16 at 6:57
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While van-der Wall forces contribute to the frictional force, they are not the only reasons. Other secondary inter-molecular forces like electrostatic attractions, polar interactions, hydrogen bonding and more also play a significant part. Apart from this features on the surface of materials, present as abrasions are also responsible for locking together and resisting change. The case of a gecko sticking to wall is not just about these forces and interlocking, but more about how the wrinkles on feet of a gecko act as several small vaccum cups which provide it the stability of sticking upside down as well(think how friction plays almost no role here)

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