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Forces and friction

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  1. Apr 16, 2015 #1
    1. The problem statement, all variables and given/known data
    A student measures the the force required topull a box along the floor and then the force required to lift the box onto a table. Which is greater?



    2. Relevant equations


    3. The attempt at a solution

    Is it the force to lift the box since frictional force is the normal force or weight times the coefficient of friction which is between 0 and 1?
     
  2. jcsd
  3. Apr 16, 2015 #2

    SammyS

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    The coefficient of friction can be greater than 1.
     
  4. Apr 16, 2015 #3
    Is there a reference saying that the coefficient of kinetic friction can be greater than 1?

    Chet
     
  5. Apr 16, 2015 #4

    SammyS

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    It is highly unusual even for static friction.

    I have seen a few values listed with μk > 1 .

    Al on Al showed 1.3 & 1.4 in a couple of tables.

    Lead on steel in one or two tables -- I don't recall the value.

    I don't why intrinsically that it's not possible for μk > 1 , but I don't have any good references.
     
  6. Apr 16, 2015 #5
    Thanks. Very interesting. I'll file this away in my brain.

    Chet
     
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