Rotating surface/friction question

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SUMMARY

The discussion centers on the mechanics of rotating surfaces and the transition from kinetic slipping to static sticking. The critical equation derived is μ*m*g > m*ω²*r, which establishes the boundary condition for slipping. The conclusion drawn is that the transition occurs from the outside in, meaning that slipping begins outside the critical radius defined by r < μ*g/ω². This understanding is essential for accurately predicting the behavior of objects on rotating surfaces.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with concepts of static and kinetic friction
  • Knowledge of rotational dynamics, specifically angular velocity (ω)
  • Basic algebra for manipulating inequalities
NEXT STEPS
  • Study the principles of static and kinetic friction in detail
  • Learn about rotational dynamics and angular momentum
  • Explore the effects of varying coefficients of friction on motion
  • Investigate real-world applications of friction in rotating systems
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This discussion is beneficial for physics students, mechanical engineers, and anyone interested in the dynamics of rotating systems and frictional forces.

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Homework Statement


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The Attempt at a Solution


Hey guys, I understand how to find the static friction point (equate mv2/r to max static friction). However, I'm confused as to which direction (in to out or out to in) is the correct one ie. from kinetic slipping to 'sticking'. At the moment I'm thinking it's outside in (Jo's answer) but I can't justify it properly. Thanks!
 
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You've determined the boundary where it starts to slip. And the boundary is dependent on

μ*m*g > m*ω²*r

or

r < μ*g/ω²

This means that outside this distance it slips doesn't it? If the aim is to have it slip until it grabs then ...
 

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