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Homework Help: HELP: Equilibrium & Torque

  1. Dec 10, 2004 #1
    1) Give the conditions for the equilibrium of an extended object.
    An extended object is at equilibrium when no force is acting on it.

    2) A uniform ladder of length 6.0m and mass 12.0kg is placed against a smooth vertical wall. The ground is rough.

    a) Calculate the force on the ladder from the wall.
    vertical forces = 0 = N1 - W
    so N1 = 117.72
    horizontal forces = 0 = F - N2
    Total Torque = 0
    0 = F(0) + N1(0) + (12*9.81*cos60*(6/2)) - (N2sin60(6))
    so, N2 = 33.98 Newtons

    b) Find the minimum coefficient of friction of the ground.
    F - 33.98 = 0 ---> F=33.98
    friction > F1/N1
    so, coefficient of friction=33.98/117.72 ----> 0.289

    Are my answers correct? If not, what did I do wrong. Please help. Thanks! :smile:
     
    Last edited: Dec 10, 2004
  2. jcsd
  3. Dec 10, 2004 #2

    dextercioby

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    I'm not going over your problem,but my guess is that:
    An extended object is at equilibrium when the resulting momentum of all forces acting on it is nil and the result of all forces acting on it is nil.
    It's placing a zero at the left of the dynamics' second law for the rotation movement and for the translation one.
     
    Last edited: Dec 10, 2004
  4. Dec 10, 2004 #3
    What's nil ?
     
  5. Dec 10, 2004 #4

    dextercioby

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    ZERO,NAUGHT,NOTHING,ZIP,LOVE ?????????????
    Don't u like football??
     
  6. Dec 11, 2004 #5
    Can someone help me check my work on the other problems, and tell me if they are correct?
     
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