Moment of inertia tensor about y-axis of a cylinder.

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SUMMARY

The discussion focuses on determining the ratio of height to radius of a cylinder such that every axis is a principal axis with the center of mass as the origin. The moment of inertia tensor is central to this analysis, specifically the equation I_yy = ∑ m (x² + z²). The participant calculated I_zz as MR²/12 but noted that this value is incorrect and requires adjustment. The use of cylindrical coordinates is recommended for the integration process to accurately derive the moment of inertia tensor.

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Homework Statement



What must the ratio of height to radius of a cylinder be so that every axis
is a principal axis (with the CM as the origin)?

Homework Equations



Moment of inertia tensor.
I need I_yy = \sum m *(x^2 + z^2)

The Attempt at a Solution



I calculated I_zz = MR^2 /12 . Now I change the principal axis to y-axis. I need to determine the moment of inertia tensor of it. Polar coordinates won't work. If I go for cartesian, I do not know the limits for the dx.
 

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You can perform the integral using cylindrical coordinates ##\vec{r} = (r\cos\theta, r\sin\theta, z)##.
 
Also, the result for ##I_{zz}## is not correct. You should get a different factor than 12 in the denominator.
 

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