Peter, You should be able to provide the inertia (I, P) about a point P other than the mass center of the rigid body. So in your code "mass center" does not have to equal "P". But, I never really do that so it could be that the underlying code doesn't apply the parallel axis theorem correctly. It isn't a feature that is likely used much, if at all. If you have an example that shows it doesn't work, then providing that on the SymPy issue tracker would be helpful so we can find and fix the bug.
Jason moorepants.info +01 530-601-9791 On Thu, Jun 23, 2022 at 1:44 PM Peter Stahlecker <peter.stahlec...@gmail.com> wrote: > I = me.inertia(A, iXX….) gives the inertia in the (normally) body - fixed > frame A > Body = Me.RigidBody( ‚Body‘, mass center, frame, mass, ( I, P)) > > My question: Does RigidBody ‚assume‘, that mass center = P ? > > Reason behind my question: > For regular homogenious bodies, iXX, IYY, etc are often known relative to > the geometric center of the body. > If the mass center is not equal to the geometric center of the body, would > RigidBody know, that the inertia is relative to the geometric center? > > In my program, the kinetic energy comes out right, if I set mass center = > geometric center, but incorrect if I do not. > Therefore, I wonder, whether there is a mistake in my program, or whether > RigidBody assumes that P = mass center. > > Thanks a lot for any help! > > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/0d3101eb-1fe7-4c24-a125-bab8c8a58145n%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/0d3101eb-1fe7-4c24-a125-bab8c8a58145n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAP7f1Ag%2BpEFeUUs%3Duvn8V8enFmm4F6z9m4h6JEfRFXR-q0SEdg%40mail.gmail.com.
