The Physics of Friction: Why Rough Wood Has More Friction

[ShootingStars]

in my mind i am thinking

smooth wood - more contact between object and surface - more friction
rough wood - less contact b/t object and surface - less friction

can someone explain why this is wrong; why rough wood has more friction?
i know rough wood WOULD have more friction but need to know why...

btw i am in physics 11, so please do not explain in terms i can't understand >_<

 

[tiny-tim]

Hi ShootingStars!

I'd say the rough wood has more sticky-up bits, and they get pushed out of the way like tiny springs, and bounce back, and that is inefficient and wastes energy …

smooth wood has fewer or smaller sticky-up bits, and so less energy is wasted.

 

[TVP45]

If you don't get into serious plastic deformation, fricrion is almost independent of contact area. Can you provide any data about your question? The coefficient for wood is usually difficult to measure and has poor repeatability.