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Circular Motion and Static Friction

  1. Oct 20, 2009 #1
    1. The problem statement, all variables and given/known data


    A small metal cylinder of mass m=0.20 kg sits on a rotating turntable. The coefficient of static friction between the metal cylinder and the turntable is us=.08. The cylinder is located 0.15m from the center of the turntable. Find the maximum speed that the cylinder can have without skidding. Acceleration due to gravity equal 9.81 m/s^2.



    2. Relevant equations

    F=MA
    Fmax=us x normal force
    Aradial=V^2/r

    3. The attempt at a solution
    Fmax=.08 x 9.81
    Fmax=.7848

    A=F/m
    A=.7848/.2
    A=3.94

    Tangenitial acceleration equals zero so.

    3.94=V^2/.15
    V=.767 m/s

    but i dont think this is correct. What am i doing wrong?

    Any help is appreciated.
    Thanks
     
  2. jcsd
  3. Oct 20, 2009 #2

    Delphi51

    User Avatar
    Homework Helper

    Likely you just forgot the mass when you did
    Fmax=μmg = .08 x 9.81
    Just a suggestion from an old timer - it is often helpful to separate the big picture from the details. I would begin this problem by writing the slipping condition:
    Fc = Ff
    then fill in the details with
    m*v^2/r = μmg
    cancel the m's and solve for v. Put in the numbers only in the last step. I can tell you that this kind of approach will serve you well when the problems get more complex.
     
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