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Homework Help: Maximum Static Friction

  1. Mar 12, 2009 #1
    1. The problem statement, all variables and given/known data
    Basically, I need to find the maximum static friction of my shoe against a wood board.
    I discovered that after increasing the slope of the board, my shoe slipped at an angle of 29.33 degrees. (using tan theta = O/A) O being 42.7 cm and A being 76 cm. The shoe has a weight of 5 Newtons. I calculated the mass of the shoe by using the formula Fg = mg, where Fg = 5, and g = 9.8. Thus: 5 = m(9.8) which equals 0.51.
    A quick recap:
    theta = 29.33 degrees
    weight (Fg) = 5
    mass = 0.51

    I am supposed to find the Maximum Static Friction of my shoe against the wood. I do not[b/] know the co-efficients of either (we are not supposed to use them from out text's)

    2. Relevant equations

    tan theta = O/A

    Fg = mg

    Ff = u Fn (u is miu or the frictional co-efficient)

    3. The attempt at a solution

    Here is a diagram depicting my work so far.

    I am basically stuck. Any help would be great (formulas, tips, anything)

    Thanks guys and gals

  2. jcsd
  3. Mar 12, 2009 #2
    Your diagram misses a coordinate system. Try to think of a coordinate system that would make the problem easier. Specifically, a coordinate system in which one or more of the forces acted entirely in the X or Y direction. Once you break the forces into their x/y components you can then use the equations you listed.
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