Parallel-axis theorem

  • Thread starter Niles
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  • #1
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Homework Statement


If I have a solid sphere (I = (2/5)MR^2) and it rotates around a point on an axis that is 5m away (it has radius 0.1m) - is the moment of inertia then: I = (2/5)MR^2 + M*(4.9m)^2?

My question is - does the parallel-axis only work when we are moving the axis of rotation around "inside" the body or also outside it?
 

Answers and Replies

  • #2
Doc Al
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It works inside or outside. I'd say that I = (2/5)MR^2 + M*D^2, where D is the distance from the center of mass to the desired axis.
 
  • #3
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Of course, my bad - but thanks again. You have helped me very much.
 

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