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Homework Help: Angular momentum of the earth

  1. Apr 22, 2005 #1
    I'm stuck on the second part of a problem and can't seem to get the right answer:

    Calculate the magnitude of the angular momentum of the earth due to its rotation around an axis through the north and south poles. Treat the earth as a uniform sphere of radius 6.38*10^6 that makes one revolution in 24.0 hours. (m=5.97*10^24)

    I got the answer 1.77*10^34 but it's wrong :(
     
  2. jcsd
  3. Apr 22, 2005 #2

    Doc Al

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    Staff: Mentor

    Show your work. Explain how you got your answer.
     
  4. Apr 22, 2005 #3
    I found the moment of Inertia (mr^2) to be = 2.43*10^38. Then found the angular velocity to be (2pi)/(24*60*60). Using the equation I=m*r^2, I got 1.77*10^34
     
  5. Apr 22, 2005 #4

    Doc Al

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    That's the moment of inertial of a particle, not a solid sphere about its center. The one you want is [itex]I = 2/5 m r^2[/itex].
     
  6. Apr 22, 2005 #5
    Thanks for that! I tried looking on the internet for the moment of Inertia of the earth and was getting all sorts of weird numbers no wonder it wasn't working.
     
  7. Apr 22, 2005 #6

    jtbell

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    Every "General Physics" textbook I've ever seen has a table of formulas for moment of inertia of various shapes of objects. What kind of a course are you taking?
     
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