@Kate there's only one center of gravity, but where its located can vary, depending on the situation

with a barbell I reckon we often assume it to be fairly constant, even though positioning your hands asymetrical is going to effect what forces are into play

For example, if you move one hand closer to the center, the weight on that side will have a larger moment arm and if unbalanced, would make the other side go up. Off course the other hand will prevent it from doing so, but the forces are completely different

Even with dumbbells there is only one center of gravity for your body, which will be higher, because the dumbbells are now part of the system. But you could break it up into smaller parts. In the end its just a model of reality, because else you'd have to start taking muscles, tendons and their insertion points into account and whatnot.

The whole discussion is missing the point completely, instead of working towards a good answer it is nit picking about terminology

Distribution of mass makes a difference in controlling the equipment, that is indisputable

Well I have no experience with lifting weights, so I can only theorize @Informaficker

There will always be people who chose the wrong words, be it because they simply are not using english as a first language or are just confusing things. Although DMoore is a bit stubborn, it would be better to point him towards the right wording instead of accusing him of being completely wrong.

And while I think that your physics question should be asked on physics.SE, I think the other question is perfectly fine, especially because it isn't a physics question but probably just about low quality plates with high differences between individual weights.

@Kate As soon as you hold a piece of equipment, you can no longer really speak of the center of gravity of that piece of equipment, because its attached to something

If its in free fall it would rotate around its center of gravity, in the middle of the handlebar

If you hold it on one side, its no longer in freefall, but you get a moment arm from the weights on the end to the point where you're holding it

The arm and weight combined have a different center of gravity

nbviewer.ipython.org/urls/raw.github.com/duartexyz/bmc/master/…

I guess your point is that if you model an arm (perhaps + weight), like this, each segment on its own still has the same center of gravity

Finally found my source! nbviewer.ipython.org/urls/raw.github.com/duartexyz/bmc/master/…

The mathematical definition for the center of mass (or barycenter) of a system with N objects (a system of particles), each with mass mi and position ri is:

Basically you're asking whether the green dot will change: no. I'm claiming the red dot will change, but that's logical, because you're changing the entire diagram if you move your hands

So we were just talking about different things

Yet another reason why terminology is important :)