The discussion revolves around a physics problem involving a hollow rod and a point mass sliding within it, focusing on angular and linear motion after an impact. The problem is set in the context of rotational dynamics and conservation laws, specifically addressing the effects of an elastic collision and subsequent motion of the mass within the rod.
The conversation is ongoing, with participants providing insights and corrections to each other's reasoning. Some have offered guidance on the correct application of conservation laws, while others are still seeking clarification on specific aspects of the problem. Multiple interpretations of the equations and assumptions are being explored without a clear consensus yet.
Participants note that the problem may involve complexities due to the elastic nature of the collision and the constraints on the rod's motion. There is also mention of potential confusion regarding the impulse of the reaction forces and the definitions of the velocities involved.
The terms is an error, i tought that ## R - x_{CM} ## was the radius of the circumference along which the system rotates.Delta2 said:This looks good
You have to take the angular momentum around the CM of the system. And also the total moment of inertia around the CM of the system. I can't understand what the term ##I_{TOT}V_{CM_y}(R-x_{CM})## is about?
Ummm ok.Delta2 said:To be honest i am not sure myself either at this point, i think the correct equation is $$-m_0v_0(R-x_{CM})=I_{TOT}\omega_{CM}$$, where ##I_{TOT}## the moment of inertia of the system around the CM.
Ok thanks for your patience, but this problem was difficult as f*ck.Delta2 said:Yes it is correct.
Ah yes, it wouldn’t make it back to A if it were not elastic.Delta2 said:If we don't make this assumption, then a mini paradox will appear if we do the balance of the kinetic energy when the particle returns to A. Somehow the total kinetic energy will be increased (in point A , with regards to point B after the inelastic collision), and we won't be able to infer where this surplus "ghost" energy has come from.
Thanks for resolving the paradox, if i tell you that i spend part of last night before sleep thinking where does the surplus of kinetic energy comes from you ll laugh with me won't you?haruspex said:Ah yes, it wouldn’t make it back to A if it were not elastic.
University.Delta2 said:Yes i agree, quite hard problem, testing to the extreme the understanding of concepts and principles.
Is it college level or university level exams this is from?