High School Inertia of a rolling dumbell

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The moment of inertia of a dumbbell, consisting of two plates of equal mass on a rod, is not affected by changing the distance "R" of the plates from the center, provided the mass of the bar remains constant. This holds true when the dumbbell rolls in a straight line. However, if the rotation occurs about an axis that is not parallel to the rod, the moment of inertia would be influenced by the distance of the weights. Therefore, the configuration of the weights matters only under specific rotational conditions. Understanding these principles is essential for accurate calculations in physics.
yunica
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How does the distance by which two plates are placed from a dumbell's center affect inertia
Hi guys,
I was just wondering this question: say I have a dumbell which is two plates of equal mass placed on a rod, then is the moment of inertia for this object affected when the distance the plates are placed from the center "R" changes?

I've attached an image to illustrate me point
1748650947950.webp


Thanks guys
 
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yunica said:
... is the moment of inertia for this object affected when the distance the plates are placed from the center "R" changes?
No.
If the mass of the bar is constant, and it rolls in a straight line, then the separation of the weights will not determine the inertia.
 
Unless it is rotating about an axis that is not parallel to the rod
 

Thread 'Reference frames, center of rotation, etc'

Topic about reference frames, center of rotation, postion of origin etc Comoving ref. frame is frame that is attached to moving object, does that mean, in that frame translation and rotation of object is zero, because origin and axes(x,y,z) are fixed to object? Is it same if you place origin of frame at object center of mass or at object tail? What type of comoving frame exist? What is lab frame? If we talk about center of rotation do we always need to specified from what frame we observe?
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