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Homework Help: Changing your center of mass

  1. Oct 28, 2012 #1
    1. The problem statement, all variables and given/known data
    To keep the calculations fairly simple, but still reasonable, we shall model a human leg that is 92.0cm long (measured from the hip joint) by assuming that the upper leg and the lower leg (which includes the foot) have equal lengths and that each of them is uniform. For a 70.0kg person, the mass of the upper leg would be 8.60kg , while that of the lower leg (including the foot) would be 5.30kg .
    Find the -coordinate of the center of mass of this leg, relative to the hip joint, if it is stretched out horizontally.

    2. Relevant equations
    xcm= (maxa +mbxb)/(ma+ mb)

    3. The attempt at a solution
    xcm= ((8.6*23) + (5.3*69))/ (13.9)=40.5cm

    However, this has come back as incorrect. Where do I go from here?
  2. jcsd
  3. Oct 28, 2012 #2


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    Science Advisor
    Homework Helper

    hi flip290! :smile:
    looks ok to me :confused:

    have you tried two significant figures? ​
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