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Homework Help: I need help with a problem dealing with static friction

  1. Oct 19, 2008 #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=.800. The cylinder is located 0.15m from the center of the turntable. Find the maximum speed that the cylinder can have without skidding.

    2. Relevant equations

    Not sure what equations will be needed

    3. The attempt at a solution

    Have no idea how to find the solution! This is on a practice test that I am working on for an upcoming physics test, but I have never seen a problem like this before. I would really appreciate a good explanation as to how to do this problem so that I will understand how to do it for the test! Thank you for all of your help!

    PS: The answer to this problem is 1.1 m/s. I just need to understand how to get to this answer.
  2. jcsd
  3. Oct 19, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Start by analyzing the forces that act on the cylinder and the kind of motion it executes as the turntable rotates. What does Newton's 2nd law tell you? Hint: The maximum value of static friction is given by what formula?
  4. Oct 19, 2008 #3
    There is an equation that tells you the maximum static friction that the object can experience. This friction, becaues it is rotating, heads towards the center of the circle. If you know the maximum static friction and the equation that deals with forces acting towards the center of the circle, you can solve for maximum velocity.

    Note that I keep on saying maximum everything. The object can be going at a slower speed and just have weaker force towards the center. If you go higher then the maximum, however, the friction force won't be able to handle to motion, and the object will shoot out tangent to circle it traces in its motion.
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