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Moment of inertia of this body

  1. Jan 10, 2017 #1
    1. The problem statement, all variables and given/known
    See attachment , it only gives me length of rod and it's mass and radius of sphere and its mass and the place of the axis

    2. Relevant equations
    I=mr^2

    3. The attempt at a solution
    I tried to get the moment of intertia of rod by integration from -L/4 to 3L/4 , but i cannot get the intertia of sphere around the axis ,
     

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    Last edited by a moderator: Jan 10, 2017
  2. jcsd
  3. Jan 10, 2017 #2

    berkeman

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    Can you post a better image please? That one is way too dark to read...
     
  4. Jan 10, 2017 #3
    IMG_0498.JPG
     
  5. Jan 10, 2017 #4

    haruspex

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    You should not need to do any integration. For such a question, I would expect to be allowed to quote standard formulas for moments about mass centres and apply the parallel axis theorem.
     
  6. Jan 10, 2017 #5
    by this equation ( Inertia at axis =Inertia at axis from centre of mass + mass*distance between the two axis^2 ) ??
     
  7. Jan 10, 2017 #6

    haruspex

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    Yes.
     
  8. Jan 10, 2017 #7
    Thank you for telling me the way of parallel axis theorem i wasn't know it , my physics professor in university didn't tell us anything about it and he puts it in an exam
     
  9. Jan 10, 2017 #8

    haruspex

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    That's quite an omission. All good now?
     
  10. Jan 10, 2017 #9
    Yeah , thank you so much.
     
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