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Constant Angular Acceleration

  1. Apr 12, 2008 #1
    A flywheel has a constant angular acceleration of 2 rad/sec^2. During the 19 sec time period from t1 to t2 the wheel rotates through an angle of 15 radians. What was the magnitude of the angular velocity of the wheel at time t1?

    Hint: let t1=0 sec, and t2=t

    [tex]\vartheta - \vartheta_{0} = \omega_{0} t + \alpha t ^{2}[/tex]

    My Work:
    [tex](15 radians) - (0 radians) = \omega_{0} (19 sec) + (2 \frac{rad}{sec^{2}})(19 sec )^{2}[/tex]

    [tex](15 radians) - (2 \frac{rad}{sec^{2}})(19 sec )^{2} = \omega_{0} (19 sec)[/tex]

    [tex]\frac{(15 radians) - (2 \frac{rad}{sec^{2}})(19 sec )^{2}}{(19 sec)} = \omega_{0}[/tex]

    [tex]\omega_{0} = (-18.2)\frac{rad}{sec} = (18.2)\frac{rad}{sec} \ for \ magnitude; \ at \ t1[/tex]

    Did I do everything right?
    Last edited: Apr 12, 2008
  2. jcsd
  3. Apr 12, 2008 #2

    Tom Mattson

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    Staff Emeritus
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    Gold Member

    You're good up to here.

    You've miscalculated. You should get something close to 37 rad/s for the magnitude.
  4. Apr 26, 2008 #3
    I think your equation is wrong

    Should it not be

    theta(final) - theta(initial) = time * angular velocity(initial) + (1/2) * angular acceleration * time^2.

    similar to the equation in linear motion?
  5. Apr 26, 2008 #4

    Doc Al

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    Staff: Mentor

    You are right.
    That should be:
    [tex]\vartheta - \vartheta_{0} = \omega_{0} t + (1/2)\alpha t ^{2}[/tex]
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