Friction between rotating objects

  • Context: Undergrad 
  • Thread starter Thread starter Telanor
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    Friction Rotating
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Discussion Overview

The discussion focuses on calculating friction between two rotating objects, specifically a plate rotating on a table. Participants explore the theoretical aspects of this problem, including the application of torque and angular velocity in the context of friction.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant questions how to calculate friction between a rotating plate and a table, given a known coefficient of friction.
  • Another participant suggests changing to spherical coordinates and integrating over the surface as a method to approach the problem.
  • A further reply elaborates on the integration approach, proposing that dividing the plate into concentric ring-shaped segments can simplify the analysis, comparing each segment's behavior to that of a straight rod.

Areas of Agreement / Disagreement

Participants present different approaches to the problem, and there is no consensus on a single method for calculating the friction between the rotating objects.

Contextual Notes

The discussion does not clarify specific assumptions or limitations regarding the model of the rotating plate or the nature of the friction involved.

Telanor
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In physics, we learned about friction between one object sliding across another, but when we got to torque and angular velocity, etc, there was never any mention of how to calculate friction between 2 objects rotating in place. Say you have a plate on top of a table and it is rotating about the center of the plate. How would you calculate the friction between the plate and the table if the coefficient of friction is known?
 
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change to spherical coordinates and integrate over the surface.
 
malawi_glenn said:
change to spherical coordinates and integrate over the surface.

Yes … specifically, if you divide the plate into concentric ring-shaped bits, each bit of length 2πa will have the same behaviour under friction as a straight rod of the same mass and of length 2πa. :smile:
 
Thank you guys for your help. I am going to see if I can figure out this problem I was working on now
 

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