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Homework Help: Rotational dynamics and coefficient of friction

  1. Jan 4, 2010 #1
    How do you find the minimum coefficient of friction needed to prevent slipping for part a and part b.

    A hollow spherical shell of mass 4.00 kg rolls without slipping down a 38.0° slope.

    (a) Find the acceleration.
    3.62 m/s2
    Find the friction force.
    9.64 N
    Find the minimum coefficient of friction needed to prevent slipping.

    (b) How would your answers to part (a) change if the mass were doubled to 8.00 kg?
    3.62 m/s2
    Friction force
    19.31 N
    Coefficient of friction

    for part a I already tried setting mgsinθ-μmgcosθ = 0
    and got 0.781 but it was wrong.
  2. jcsd
  3. Jan 4, 2010 #2
    If you're looking for a coefficient of friction that will prevent slipping then the object won't move at all. This sounds alot to me like static friction.

    EDIT: I think I'm confused with what you mean by slipping, can you elaborate a litte bit?
  4. Jan 4, 2010 #3
    If you've already found the frictional force, you just need to find the normal force between the shell and the surface and then solve the formula:
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