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Centre of Mass/Volume


lamensterms
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Hi,

 

Just wondering if someone could please check my centre of mass/volume for the attached solid?

My understanding is for uniform material, the centre of mass should be the same as the centre of volume.  If I slice my solid at my centroid - the resultant solids are not of equal volume.  What am I missing?

 

image.png.3c4330cce3a207856d19648baa323fcc.pngCentre of Volume.dwg

 

Thanks

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I don't know if this will help you, but this is what MASSPROP told me about the 2 Solids when selected together.  Is there a reason you have not joined them?  🤔

Or might I ask , "Is there a reason I wasn't paying attention when I read your post?"  :beer:  :beard:

 

image.thumb.png.c603aea473fdd4c2d0a670dd5085c3e4.png

Edited by Dadgad
asleep at the wheel
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I should think that they WOULD be the same, were it not for the nonsymmetric voids.  :|

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The location of the centroid for a 3D shape is the same as the center of mass for an object of uniform density is the same as the center of gravity for an object of uniform density in a uniform gravitational field.  However, the these points do not define the 3D shape's center of volume.  The centroid is a function of the distribution of the volume.  For example, the solid shown below (an extruded 2D shape) has it's centroid located at the noted point. The volume to the left of the red line is almost twice as much as the volume to the right.

image.thumb.png.3b5bde373231a82c11f70fc84695cabf.png

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Thanks for the replies guys!

@Dadgad - yep, MASSPROP gave me the same centroid as ProSteel's COG tool... which is different to your results.  Can only guess you might not have been in World UCS?

 

@lrm - Thanks a lot for the explanation and demonstation. That makes much more sense now, and confims my assumption about centre of mass/volume was incorrect.

 

Thank you both for the clarity!

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