
#1
Jan1210, 08:22 AM

P: 101

To which of the two cubes has a larger moment of inertia?
I think it's the right one, is it correct? How can I explain that without using the parallel axis theorem? 



#2
Jan1210, 12:10 PM

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P: 39,580





#3
Jan1210, 01:01 PM

P: 101

what relevant equation?
I think it's the right one because We know that the minimal moment of inertia is throw the principal axes that goes throw the center of mass. in the right one , the rotation isn't throw the principal axes . there is also the following theorem : The moment of inertia about an arbitrary axis is equal to the moment of inertia about a parallel axis passing through the center of mass plus the moment of inertia of the body about the arbitrary axis, taken as if all of the mass M of the body were at the center of mass. Am I wrong? 



#4
Jan1210, 04:05 PM

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P: 39,580

Moment Inertia of a cubeI'd do the 2D case first, to see if it offered some intuition. That is, the moment of inertia for a flat rectangular sheet, with the axes going straight versus diagonal. 



#5
Jan1210, 04:58 PM

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Thanks
PF Gold
P: 11,521

I think they'll turn out to be equal. Try computing the moment of inertia tensor.



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