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Measurements - relation between mass and size

  1. Oct 5, 2011 #1
    1. The problem statement, all variables and given/known data
    Why are mammals as large as they are and not much larger?

    2. Relevant equations
    Two figures are given. One of the mammal with size S and mass M. Femur is the thigh bone of the mammal with l being the length of the femur, d being the thickness of the femur and A being the cross sectional area:
    i)l ∞ s - length of the femur is proportional to the size
    ii) m∞s3∞l3
    iii) pressure ∞ weight/Area ∞ m/d2
    iv) m ∞d2
    v) d2∞l3
    Therefore, d ∞ l 3/2
    3. The attempt at a solution
    These have been worked out, but I am confused at how length is proportional to the size. Is volume the size? In fact, I don't understand the whole thing. Please help. I have looked at the MIT video three times and still confused. Sorry for being so dumb but I don't hesitate to ask.
  2. jcsd
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