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Homework Help: Moving a block with kinetic and static friction to find the net force?

  1. Jan 27, 2009 #1
    The coefficient of static friction between a block and a horizontal floor is 0.37, while the coefficient of kinetic friction is 0.14. The mass of the block is 3.4 kg. If a horizontal force is slowly increased until it is barely enough to make the block start moving, what is the net force on the block the instant that it starts to slide?

    I tried multiple ways of solving this problem, but am only down to one attempt left for credit on my homework. I don't know if I'm over analyzing the problem or what, but its giving me trouble, please help. Thank you
  2. jcsd
  3. Jan 27, 2009 #2


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    What force is required to move the block? Or more specifically what is the greatest amount of resistance the static friction can provide?


    But that's the static friction. But that is the first part of what you want.

    After it moves then it is opposed by the μk*m*g of the kinetic friction, so ... Your net force then is Fstatic - Fkinetic.
  4. Jan 27, 2009 #3
    thanks again I owe you!
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