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Homework Help: Statics/rotational dynamics:hanging sign

  1. Apr 11, 2005 #1

    LoN

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    A sign has a mass of 1050 kg, a height h = 1 m, and a width W = 4 m. It is held by a light rod of length 5 m that is perpendicular to a rough wall. A guy wire at 23° to the horizontal holds the sign to the wall. Note that the distance from the left edge of the sign to the wall is 1 m.

    Suppose we rely upon friction between the wall and the rod to hold up the sign (there is no hinge attaching the rod to the wall). What is the smallest value of the coefficient of friction m such that the sign will remain in place?

    what i end up with is:
    f*5=4*5145, solve for f
    N=Tx=Ty/tan(23)=(Msign*g/2)/tan(23)
    f/N=u=.33957986 which according to the online HW is wrong.

    help?
     

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