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Homework Help: Angular acceleration and angular velocity

  1. Mar 15, 2012 #1
    1. The problem statement, all variables and given/known data

    Calculate the angular acceleration and angular velocity of a 4 kg object rotating in a circle of 3 m radius in a time of 6 s.

    2. Relevant equations

    3. The attempt at a solution

    Angular acceleration = ω2*r

    C=2∏r= 2*3.14*3=18.84
    360°/57.3°=6.28 rad/s
    6.28/6= 2.09 rad/sec

    Angular acceleration= (2.09)2*3=12.54???????

    Angular velocity= angular displacement/time ????

    I just want to check whether my working is correct or not.
  2. jcsd
  3. Mar 15, 2012 #2
    Nope.Its not right.

    Remember, angular acceleration is dw/dt.

    The acceleration w^2*r is centripetal accelwration.

    Infact writing angular acceleration as w^2*r is dimemsionally inconsistent.

    As nothing had been told about how w changes with time nothing can be said about angular acceleration.

    In such cases w is assumed to be constant making angular acceleration 0
  4. Mar 16, 2012 #3
    angular acceleration = 0

    what about angular velocity?
  5. Mar 16, 2012 #4


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    Science Advisor
    Homework Helper

    Hi John78! :smile:
    Your formula …
    … is fine :smile:
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