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Homework Help: Physics question - if you had a smooth wood block, why is rough surface more friction

  1. May 16, 2009 #1
    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 cant understand >_<
  2. jcsd
  3. May 16, 2009 #2


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    Hi ShootingStars! :smile:

    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. :wink:
  4. May 16, 2009 #3
    Re: physics question - if you had a smooth wood block, why is rough surface more fric

    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.
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