Can somone explain this review solution (moments/inertia)?

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SUMMARY

The discussion centers on the calculation of moments of inertia, specifically addressing the confusion surrounding the multiplication of 1/3 in the context of a rod's center of inertia. Participants clarify that the calculation involves three sides of length 0.2m, with two sides rotating about one endpoint, justifying the use of the 1/3 factor and the coefficient of 2. The middle bar's contribution is simply calculated using the formula mr², as it is parallel to the axis of rotation. This highlights the importance of understanding the geometry and axes involved in moment of inertia calculations.

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whitejac
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Homework Statement


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Homework Equations


This would be the part I think I'm missing

The Attempt at a Solution


In the fourth line, Ix, where is the justification for multiplying 1/3 by the first term? I believe they are using the center of inertia of a rod, which is mr2 and the first term doesn't make much sense. Could someone explain to me the justification of that line?
 
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whitejac said:
In the fourth line, Ix, where is the justification for multiplying 1/3 by the first term?
There seems to be some confusion over the axes. They must mean Iy.
The part that matters is just the three sides of length 0.2m. Two of them are rotating about one endpoint, hence the 1/3 and the factor 2 at the front. The middle bar is parallel to the axis, so just mr2 for that piece.
 

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