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Homework Help: Time-dependent angular acceleration problem

  1. Mar 28, 2010 #1
    1. The problem statement, all variables and given/known data

    As a result of friction, the angular speed of a
    wheel changes with time according to
    dθ/dt=ω0*e^-σt ,
    where ω0 and σ are constants. The angular
    speed changes from an initial angular speed
    of 3.96 rad/s to 3.46 rad/s in 3.92 s .
    Determine the magnitude of the angular
    acceleration after 2.44 s.
    Answer in units of rad/s2

    2. Relevant equations
    dω/dt = [tex]\alpha[/tex]

    3. The attempt at a solution
    I've tried differentiating the given expression for omega in an attempt to get the angular acceleration, but that didn't work because [tex]\sigma[/tex] is undefined in the problem. I've also tried taking the ln of both sides, but that didn't work either. I tried solving for [tex]\sigma[/tex] in terms of ω and ω0, but that didn't work. Finally, I tried just assuming that the acceleration is just constant from t0 to t, but that also wasn't the right answer. So, I have no idea what to try next......
    Last edited: Mar 28, 2010
  2. jcsd
  3. Mar 28, 2010 #2
    I still can't get it O_O
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