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Answer check please - Moment of Inertia Calculations

  1. Jan 14, 2014 #1
    Answer check please -- Moment of Inertia Calculations

    For question 1 I got T=mnut * r pulley * gravity

    For question 2 I got Isystem = 1/2 M(R23 + R24 + m (R21 + R22)

    First day of physics lab and I just wanted to double check that these are correct.

    Thanks.
     

    Attached Files:

  2. jcsd
  3. Jan 15, 2014 #2

    tiny-tim

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    hi ktvphysics! welcome to pf! :smile:

    (1 is fine)

    i think you're misunderstanding the diagram for 2 …

    the CD and the washers both have holes in the middle :wink:

    also (although the question doesn't say), it must be asking for the moment of inertia about the centre, so you'll have to use the parallel axis theorem for the two washers!
     
  4. Jan 15, 2014 #3
    So the answer to 2 would be:

    Isystem = 1/2 M(R23 + R24) + 2[1/2m(R21 + R22) + md2]

    That corrects the problem about the Parallel Axis Theorem, but I'm confused about what you were saying about the holes in the middle. I used the moments of inertia for hollow cylinders for the CD and Washers, which is essentially what each of them is.
     
    Last edited: Jan 15, 2014
  5. Jan 15, 2014 #4

    tiny-tim

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    hi ktvphysics! :smile:
    sorry, i was in a hurry to go out and i misremembered the formula! :redface:

    yes, your answer is fine now :smile:
     
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