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Homework Help: Equilibrium Probelm

  1. May 28, 2009 #1
    1. The problem statement, all variables and given/known data

    A uniform wooden plank of length L = 6.0m and mass M = 90kg rests on top of two sawhorses separated by D = 1.5m, located equal distances from the center of the plank. Your cousin Throckmorton tries to stand on the right-hand end of the plank. If the plank is to remain at rest, how massive can Throckmorton be?

    3. The attempt at a solution
    How do I know the Xcg value for this problem since there are two sawhorses supporting this plank?
  2. jcsd
  3. May 28, 2009 #2


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    Uniform means that the centre of gravity is at the geometrical centre of the plank. In this case, half of it's length.
  4. May 28, 2009 #3
    So even if there's a weight at the end of the plank, the center of gravity will still be at (L/2)?
  5. May 28, 2009 #4


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    the cg of the plank is at L/2. The cg of the system (plank and cousin) changes, but you don't need to find it.
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