Bug walking around the perimeter of a lazy susan (hypothetical)

  • #1
crudux_cruo
23
11
Given a bug that's walking counterclockwise around on the surface of a lazy susan (which itself is sitting on frictionless bearings), wouldn't the the friction between the bug and the lazy susan (which is needed to be able to walk) apply torque (no matter how negligible) that accelerates the lazy susan clockwise?

I ask because I am having trouble understanding how a system like that is truly isolated and angular momentum conserved, but I'm probably overthinking it.

The bug's internal energy here is just confusing me. If I write out a hypothetical where the bug speeds up, do I still consider the chemical potential energy needed to accelerate the bug as internal?
 
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Answers and Replies

  • #2
anuttarasammyak
Gold Member
1,850
954
Alice keeps at rest in a IFR because motion of frictionless bearing does not affect her.
I wonder how bug walks on the frictionless bearing.
 
  • #3
crudux_cruo
23
11
I wonder how bug walks on the frictionless bearing.
Bug is on lazy susan, lazy susan is on the bearings.
For added context, this is a lazy susan (a rotating tray, or turntable)
turntable.jpeg


EDIT:

The torque from friction on the bug is the same as the torque from friction on the table, which would have been obvious earlier if I thought about them for more than five seconds and realized they were third law pairs internal to a system. So assuming I am correct in my line of thought, the sum of the change in momentum of the system would be zero.

This seems pretty obvious since internal forces cannot change the momentum of a system, so I think I just need to work on my understanding of internal energy and chemical potential energy (like the gas in a car, or muscular contractions) as they relate to a system.

Just leaving this edit for posterity, in the event someone thinks they spot my misconception(s) here.
 
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