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Homework Help: Angular acceleration problem

  1. Aug 18, 2011 #1
    1. The problem statement, all variables and given/known data

    angular acceleration of line a= -2w^2 rad/s

    when theta=pi/6, w= 10 rad/s

    what is angular velocity when theta= pi/3?

    2. Relevant equations

    chain rule

    3. The attempt at a solution

    w= e^-2theta is my answer, but I know this is wrong

    I know that this question is really easy, but I just don't know how to get it
  2. jcsd
  3. Aug 18, 2011 #2


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    Homework Helper

    Well you should know that α= -2ω2 means that dω/dt = -2ω2

    which is an easily solvable DE once you 'separate the variables' i.e. put all the things with ω on one side and t on the other then integrate both sides.
  4. Aug 18, 2011 #3
    But then I end up with t=1/2w, how do I find the rest of the answer?
  5. Aug 18, 2011 #4
    Someone please help me!!!!
  6. Aug 18, 2011 #5


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    Homework Helper

    I now saw that you have ω and θ so forget my above post and replace α with ω*dω/dθ and integrate again. Do not forget the constant of integration which you can find with the conditions they gave you.
  7. Aug 18, 2011 #6
    Yes, that was my problem all along... I forgot to add the constant!! Thanks.
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