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Homework Help: I need to to find the moment of inertia for the system

  1. Nov 19, 2008 #1
    1. The problem statement, all variables and given/known data

    2 kg uniform rod of length 1m is constrained to rotate about a horizontal axis passing through its center. The rod has a 1.5 kg point mass attached to one end and a 0.5 kg point mass attached to the other end. The 1.5 kg mass is given a downward push so that it starts moving with an initial velocity of 1.2 m/s.

    Ok I used the equation of moment of inertia or rotational inertia

    Here's what I did
    m1=.5 kg
    m2=1.5 kg
    r=1/2 because L =1m and the center of mass is in the middle of the rod
    thus I plugged in the variable

    I=.5(1/2)^2 +1.5(1/2)^2
    =.5 kg*m^2

    is that right

    and next i have to find the initial kinetic energy and then i have to find the total angle of it coming to rest. I need help
  2. jcsd
  3. Nov 20, 2008 #2


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    Science Advisor
    Homework Helper

    Hi afcwestwarrior! :smile:

    (have an omega: ω :wink:)

    Yes, your I is right … but don't forget to add on the I of the rod itself! :wink:

    Now use rotational KE = (1/2)Iω2,

    and PE + KE = constant. :smile:
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