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Moment of Inertia question (dead simple)

  1. Jan 12, 2014 #1
    1. The problem statement, all variables and given/known data
    A thin disk is 100g.
    It's diameter is 20cm.
    It's thickness is 2cm.

    Rotation is about the central axis (ie. perpendicular to the symmetrical plane).
    Answer in kg*m2

    2. Relevant equations

    I=(1/2)MR2
    M is the mass
    R is the radius
    I is the moment of inertia

    3. The attempt at a solution

    R = half the diameter ∴ R = 10cm

    I= (.5)(.1)(.1)2
    I= 0.0005 = 5*10^-4


    I don't think the thickness matters as long as it is symmetrical all around.

    The reason I ask is because this question is a multiple choice question for marks, but the answer I found (0.0005) wasn't listed as one of the options. Thanks!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 12, 2014 #2

    SammyS

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    What are the possible options?
     
  4. Jan 12, 2014 #3
    5E-6
    1E-7
    5E5
    2E-5
    1E4

    Where the letter E indicates scientific notation.
     
  5. Jan 12, 2014 #4

    haruspex

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    I agree, it's 5E-4.
     
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