# Rod on a Plane: Calculating Angular and Linear Motion After Impact"

• Nexus99
In summary, A hollow rod closed at the ends A and B, has mass M and length R. The rod is free to rotate on a horizontal frictionless plane around the z axis passing through A and coming out of the sheet. A body can slide without friction inside the cavity point mass m. Initially the rod is stationary and the mass m is placed, also stationary, at a distance negligible but finished by A. A ball of mass m0, with velocity ##\vec{v_0}## = (0,-v0, 0), elastically hits it in B. Calculate:1. the speed of the ball ##\vec{v_1}## and the angular speed ##\vec{\
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?

Lnewqban
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.
Ah yes, it wouldn’t make it back to A if it were not elastic.

Delta2
haruspex said:
Ah yes, it wouldn’t make it back to A if it were not elastic.
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?

Lnewqban
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?
University.

Delta2

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