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Homework Help: Rotational Kinematics (String attached to disk)

  1. Nov 27, 2012 #1
    1. The problem statement, all variables and given/known data
    Determine the relationship between the angular
    acceleration of the flywheel, the downward acceleration of the block, and the radius of
    the ring.

    Known data:
    Mass Ring: 1.420 kg
    Radius Ring (Inside, then Outside): 5.10 cm, 6.325 cm
    Mass Disk: 1.455 kg
    Radius Disk: 11.45 cm
    Mass Shaft: Negligable
    Radius Shaft: 0.6 cm

    2. Relevant equations

    ω=ω0 + αt

    3. The attempt at a solution
    I'm really lost on this, i assume that i need to calculate the tension the block places on the string (F=MA)? Could anyone give me a hint on how to get started on this.

    Attached Files:

  2. jcsd
  3. Nov 27, 2012 #2

    Simon Bridge

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    Welcome to PF;
    Your wish is my command:
    hint: draw free-body diagrams.

    Though you could use conservation of energy and assume acceleration is constant.
  4. Nov 27, 2012 #3
    I understand how to do the FBD for the hanging mass. The forces acting on it are simply Fg and Ft. How would i do a FBD for the spinning mass? Would i pick a point on the outer edge to do it for?
  5. Nov 27, 2012 #4

    Simon Bridge

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    The tension force acts at a particular location on the flywheel - creating a torque. ##\tau=I\alpha##
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