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Homework Help: Sign Convention of Moments

  1. May 16, 2012 #1
    1. The problem statement, all variables and given/known data

    I have this problem.

    http://bit.ly/JkVdxA [Broken]

    This is a thin-walled cantilever beam subjected to two loads through the shear center. I know how to do all of the calculations, the only thing I am unsure about is the sign convention of the moments caused by the two loads. We are to evaluate the moments at the midpoint of the beam (500mm into the page). I am just a bit unsure about applying the right hand rule to determine the signs of the moments about the axis (which is located at the centroid).

    2. Relevant equations


    3. The attempt at a solution

    I think it is
    Mx = -500N * 500mm = -250000Nmm
    My = -300N * 500mm = -150000Nmm

    However I found a similar example that said My was positive. Could someone please explain? Thanks. :)
    Last edited by a moderator: May 6, 2017
  2. jcsd
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