Re: [sympy] Sympy.physics.mechancis: RigidBody // inertia

2022-06-25 Thread Peter Stahlecker
Dear Jason, There is nothing wrong with *kinetic energy*, at least I could not find anything! I programmed a 3D ball rolling on a flat surface. The total energy is constant, no matter where the center of mass is. Sorry about the commotion I created! NB: I use solve_ivp to do the integration. I

Re: [sympy] Sympy.physics.mechancis: RigidBody // inertia

2022-06-25 Thread Peter Stahlecker
Dear Jason, Thanks a lot! It seems to be my program, rather than *kinetic energy*. The sample which did not work was my ‚Wackelstein‘, where there seem to be many other issues, the geometry is probably too difficult for me. I tried it on my 2D *rolling disc on an uneven street*, where the geomet

Re: [sympy] Sympy.physics.mechancis: RigidBody // inertia

2022-06-25 Thread Jason Moore
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

[sympy] Sympy.physics.mechancis: RigidBody // inertia

2022-06-23 Thread Peter Stahlecker
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 know