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Homework Help: Oscillatory Motion

  1. Sep 2, 2008 #1
    1. The problem statement, all variables and given/known data

    The moment of inertia for an arm or leg can be expressed as I = amL2, where a is a unitless number that depends on the axis of rotation and the geometry of the limb and L is the distance to the center of mass. Say that a person has arms that are 27.80 cm in length and legs that are 38.92 cm in length and that both sets of limbs swing with a period of 1.40 s. Assume that the mass is distributed evenly over the length for both the arm and leg.

    **Calculate the value of A for the person's arms.

    2. Relevant equations

    I am not sure of any equations that include Amplitude.

    Here is one that relates to the problem, but cannot be used to solve A:

    T = 2pi(sqrt(I/mgL))

    T= period given (1.4 s)
    I = ?
    L = given 27.80
    g = gravity 9.81
    m =?

    3. The attempt at a solution

    I'm just really confused on how to go about this problem? Any advice?
  2. jcsd
  3. Sep 3, 2008 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Are you sure its amplitude they want and not the little constant in the moment of inertia equation?
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