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Homework Help: Rotational motion, find the frictional force.

  1. Sep 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A small 350-g collar C can slide on a semicircular rod which is made to rotate about the vertical AB at a constant rate of 7.5 rad/s. The coefficients of friction are μs = 0.25 and μk = 0.20.

    2. Relevant equations
    Tangent Velocity= Radians*radius
    Normal acceleration an= Vt^2/radius

    3. The attempt at a solution
  2. jcsd
  3. Sep 20, 2015 #2
    Basically the collar has two forces acting on it. The rotational force and the gravitational force. I used the y axis for the force components parallel/opposite to the normal force and multiplied the normal force by the kinetic friction which should have given me the frictional force. But the computer program I'm using (Mcgraw hill) says my answer is wrong.
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