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Mechanics moments question

  1. May 29, 2014 #1
    chfh.png

    For figure 1.2, if you take moments at the point where H acts, then you get (assuming moments are positive anti-clockwise):

    -RCos(theta)(0.4) + 60(0.2) = 0

    Rearranging gives:

    Rcos(theta) = 30

    However, according to the mark scheme (which takes moments at the point where R acts) Rcos(theta) = 60

    What have I done wrong?
     
  2. jcsd
  3. May 29, 2014 #2

    SteamKing

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    About H, there is also a moment due to the horizontal component of R.
     
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