Does friction restrict motion perpendicular to the plane also?

  • #1

Main Question or Discussion Point

does friction restrict motion perpendicular to the plane also??

Friction is caused due to cold weld between the molecules of the surface and the object.So why does it only affect the motion parallel to surface. Because even when we move a body straight up the cold weld needs to be broken.
 

Answers and Replies

  • #2
Doc Al
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Friction is caused due to cold weld between the molecules of the surface and the object.So why does it only affect the motion parallel to surface. Because even when we move a body straight up the cold weld needs to be broken.
I expect the adhesion between most surfaces to be quite small, so for ordinary objects it may be neglected compared to the object's weight. But I'll bet there are plenty of applications where you cannot ignore it. (Calling all tribologists!)
 
  • #3
256bits
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Cold weld is not the term to use for the attraction of one surface to another.

Cold weld is what is says - the two surfaces are welded together, likely similar metals for instance, where the crystaline structures interlock into one another. Flakes of gold will "cold weld" together as there is not an oxide layer to prohibit one gold atom from directly contacting another gold atom. Under more excessive pressure, two metal surfaces will cold weld at certain points and galling or pitting will ocuur as one surface will remove parts of the other surface as they slide across one another.

This is not the same as what happens during regular friction.
 

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