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Homework Help: Moment of inertia and angular acceleration

  1. Mar 13, 2013 #1
    1. The problem statement, all variables and given/known data
    If the fall height of the mass is doubled, the angular acceleration of the wheel will
    a. decrease by an unkown amount
    b. remain unchanged
    c. decrease by a factor of 2
    d. increase by an unknown amount
    e. increase by a factor of 2

    2. Relevant equations

    3. The attempt at a solution
    well since angular acceleration is slope of linear graph and if we double the height(x-axis) I think the angular frequency will remain constant. But maybe I'm wrong. That is why I need help.
  2. jcsd
  3. Mar 13, 2013 #2

    Simon Bridge

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    The description is not complete.
    Fall of what and how is this related to a wheel?

    Is this a mass falls onto a wheel, where it stays somehow, and so makes it turn?
    Hint: conservation of energy.
  4. Mar 14, 2013 #3
    its a suspended mass attached to to the hub of a bicycle wheel through a pulley. so basically we release the wheel (which is attached to a table) and it turns from the weight of the suspended mass until the mass reaches the floor.
    Anyways I have come to a new conclusion that the angular acceleration doubles from the height being double.
    I still need confirmation though.
  5. Mar 14, 2013 #4

    Simon Bridge

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    Yeh - the final speed is higher, but the time is also longer.
    You need to use the kinematic equations for rotating bodies or conservation of energy if you want a mathematical approach - or you can use your understanding of gravity.

    If the mass were free to just fall - not attached to the wheel - how would the acceleration be affected by the distance it has to fall?
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