# Homework Help: Circular Motion and Static Friction

1. Oct 20, 2009

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

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. Oct 20, 2009

### Delphi51

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.