Calculating Moment of Inertia for Combined Shapes

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To calculate the moment of inertia for combined shapes, first determine the moment of inertia for each individual piece about the chosen axis, which in this case is the z-axis or the axis perpendicular to the plane. The parallel axis theorem is necessary for adjusting the moment of inertia when the axis of rotation does not pass through the center of mass. The user initially struggled with the concept but found clarity through further research and discussion. This highlights the importance of understanding both central axes and the application of the parallel axis theorem in rotational inertia calculations. Overall, effective communication and additional research can lead to a better grasp of complex physics topics.
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So, it's straight forward enough to calculate the moment of inertia of basic planes with evenly distributed mass, but if I were to say glue the red and green plane together, how would I find the moment of inertia of the blue shape?
 
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Hayden Leete said:
how would I find the moment of inertia of the blue shape?
About what axis?

You can find the moment of inertia of each piece about the axis of choice, then just add them. (You'll need the parallel axis theorem.)
 
Doc Al said:
About what axis?

You can find the moment of inertia of each piece about the axis of choice, then just add them. (You'll need the parallel axis theorem.)

probably should have specified, the z axis, or the axis perpendicular to the plane. the axis of choice is the blue COM, and I don't know how to find the moment of inertia of each shape except with central axes (I don't know much in the world of rotational inertia)
 
actually you know what, through more googling and researching stuffs, I've figured it out. I've been trying to find somewhere to explain this to me for a while now, but I didn't know exactly what to search for until your reply, so thanks for that :biggrin:
 

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