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Homework Help: Acceleration of hollow sphere rolling down table.

  1. Nov 1, 2007 #1
    1. The problem statement, all variables and given/known data

    A hollow spherical shell is rolling without slipping or sliding down a board that is tilted at an angle of 35.0° with respect to the horizontal. What is its acceleration?

    2. Relevant equations


    if an object rolls without slipping or sliding:

    v = rw

    that means that

    a = r*alpha


    3. The attempt at a solution

    I imagine the solution would be something times g sin(35) but I am not sure exactly how to go about solving this one.
  2. jcsd
  3. Nov 1, 2007 #2


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    Staff Emeritus
    Science Advisor

    Make sure the moment of inertia is correct.


    Now the mass has a force pulling it down the incline, which is the weight component parallel to the incline. The moment of inertia is resisting that force, and the friction prevents the sphere from slipping, so friction is acting at the radius in the direction opposite the translational motion parallel with the plane of the incline.

    v = rw
    a = r*alpha

    are correct.
  4. Nov 2, 2007 #3
    Thanks for the help.

    I am still a bit murky on this. I know torque=moment of inertia * radial acceleration. I need to find radial acceleration. How can I solve without knowing the torque or the mass of the object? How can I set up the problem in such a way to cancel the mass?
  5. Nov 2, 2007 #4
    I solved it:


    I am still not sure why it worked out that way. Any kind soul care to help me understand this a little better?
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