Understanding the Application of the Parallel-Axis Theorem

[Niles]

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?

 

[Doc Al]

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.

 

[Niles]

Of course, my bad - but thanks again. You have helped me very much.