Rotational Equilibrium and Rotational Dynamics problem

  1. The Question:

    A potter's wheel having a radius of 0.50 m and a moment of inertia of 12 kg m^2 is rotating freely at 50 rev/min. The potter can stop the wheel in 6.0 sec by pressing a wet rag against the rim and exerting a radially inward force of 70 N. Find the effective coefficient of kinetic friction between the wheel and the rag.

    What I know:

    I know with the info given, I must use the angular version of newton's 2nd law.

    Sum (Torque) = I(Moment of Inertia) Alpha (Angular Acceleration).

    But I am unsure how this even relates to the coeff. of kinetic friction.

    Any help???
    Thanks In Advance
     
  2. jcsd
  3. Doc Al

    Staff: Mentor

    The friction force is the tangential force producing the torque that stops the wheel. How does kinetic friction relate to the normal force, which is the force with which the potter pushes against the rim?
     
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