How do you find the center of gravity?

kai_etringer

and before you say the scales in an assembly, that shows the center of mass.

NeilCooke

What's the difference?

brucebartlett

In CAD space you would generally assume these to be the same, which they are if gravity is constant across the rigid body. If the object was large enough and rigid enough to have varying gravity, center of gravity would differ to center of mass. 

brucebartlett

yes

NeilCooke

What's the difference?

kai_etringer

the center of gravity, as I understand it, is the point in an object where if you had a magical string attached to it passing in the opposite direction of gravity (up), and nothing else but the four fundamental forces (gravity including) it would not move at all. 

https://physics.stackexchange.com/questions/50107/what-is-the-difference-between-center-of-mass-and-center-of-gravity

quoting my favorite answer: Center of gravity is the point in a body around which the resultant torque due to gravity forces vanish.

That means that for any rigid body, the two points are the same, because you can model rigid bodies in free fall as if gravity acted only on the center of mass, and forces on the center of mass make no torque.

Sorry if I explained it badly, I am not good at it. I often go to science (even though I'm not even close to an expert, not having graduated highschool yet)

brucebartlett

In CAD space you would generally assume these to be the same, which they are if gravity is constant across the rigid body. If the object was large enough and rigid enough to have varying gravity, center of gravity would differ to center of mass. 

kai_etringer

so for an ultralight aircraft, It would be, essentially, the same?

brucebartlett

yes