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Homework Help: What does this equation mean? angular acceleration

  1. Nov 8, 2016 #1
    1. The problem statement, all variables and given/known data
    I was in lab and we used a mass hanger and disk and plate attached to pulley to and a motion sensor to measure moment of inertia. Angular acceleration was recorded along with other values such as linear velocity and position and all that.

    The question is:
    the hanging mass does not fall with acceleration of gravity. Is this significant in the experiment? What does it mean if the angular acceleration is equal to gravity divided by the radius of the pulley (instead of acceleration divided by the radius?

    2. Relevant equations
    alpha = a/r

    3. The attempt at a solution

    I am not really sure why making the acceleration equal to gravity would change anything. Does this mean that there is no rotational force applied if a=g? And in that case it is just a falling object so that is why it is important that the object needs an acceleration of something other than g, because there is a force applied other than gravitational force?
    Last edited: Nov 8, 2016
  2. jcsd
  3. Nov 8, 2016 #2
    i think one should define angular velocity and see whether its changing with time and thus the rate of change of ang velocity will give you a correct description.
    draw a diagram showing ang displacement as well as linear displacement of the body causing such ang. displacement...this may help.
  4. Nov 8, 2016 #3


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    Science Advisor
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    If the angular acceleration is not equal to the linear acceleration divided by the radius you measured something wrongly. Or the cable is slipping.
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