Sympy.physics mechanics, just a question for better understanding. #26245
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I found my stupid error! |
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The program below just sets up Kane's equations for a 3D multiple pendulum. As I use Particles not RigidBody, I do not need rotations around the Z axis. The pendulums are aligned in the Z axis of their body fixed frames, called Frames[i] fo the i-th pendulum
My lack of understanding is in this portion of the program: (O is fixed in the inertial frame N)
Points[0].set_pos(O, l * Frames[0].z)
Points[0].v2pt_theory(O, N, Frames[0])
print('speed of P0 in A0:', Points[0].pos_from(O).diff(t, Frames[0]))
Points[0].set_vel(Frames[0], 0)
Unless I put this line: Points[0].set_vel(Frames[0], 0), I get an error from Kane's method like 'speed of Points[0] not given in Frames[0].
However, the line above it, print('speed of P0 in A0:', Points[0].pos_from(O).diff(t, Frames[0])) correctly prints 0.
My curiosity is only this: Kane's Method seems to "know" the speed of Points[0], but does not "use" it.
Thanks a lot for any clarification!
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