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Homework Help: Getting the avg angular vel.

  1. Nov 10, 2007 #1
    A flywheel with a radius of 0.300 starts from rest and accelerates with a constant angular acceleration of 0.600/s^2. i know how to solve for the atan but not for arad which is arad=w^2/r it ask Compute the magnitude of the tangential acceleration, the radial acceleration, and the resultant acceleration of a point on its rim at the start.


    i know its 2pi=6.28rad all the way around and its acc. at .600rad/s^2 but i dont know where to go from there
     
    Last edited: Nov 10, 2007
  2. jcsd
  3. Nov 10, 2007 #2

    Shooting Star

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    Your problem is not clearly formulated. Write clearly what is to be found out. Show your attempt.
     
    Last edited: Nov 10, 2007
  4. Nov 10, 2007 #3
    it says at the start so would thetaf and thetai be both 0?
     
  5. Nov 10, 2007 #4

    Shooting Star

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    That means final theta = 2*pi.

    w^2 = 0^2 + 2*a*(2pi). So, you know final w(omega).

    Now find the linear speed, at the circumference.
     
    Last edited: Nov 10, 2007
  6. Nov 10, 2007 #5
    so that means w^2=0^2 +2(.600)(6.283) it comes out to be w=2.86 but it says its wrong
     
  7. Nov 10, 2007 #6

    Shooting Star

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    As I said previously, your problem was not clearly formulated. How much time or what is the total angle?
     
  8. Nov 10, 2007 #7
    well if you use the w^2=Wo+2a(O-0o) its asking for the speed of the tip of the flywheel from the start so wouldnt the theta be 2xpi or just pi?
     
  9. Nov 10, 2007 #8
    i agree with shooting star.. how long was it spun or what was its angular displacement?
     
  10. Nov 10, 2007 #9
    and are u solving for the angular velocity or angular acceleration

    By the way.. can u please explain what the units of atan and arad should be? it matters...
    are atan and a rad angular acceleration or linear?
     
    Last edited: Nov 10, 2007
  11. Nov 10, 2007 #10
    thats really where im stuck on i solved the other parts of the problem asking for the atan arad at 60degrees and 120degrees but what value would i use for the start theta? 360 or 180, 0?
     
  12. Nov 10, 2007 #11
    well it starts at 0... (rest), also answer my previous post.. because thats essential... and while you are at it.. write down the problem exactly verbatim. and your attempt :D
     
  13. Nov 10, 2007 #12
    nvm yea you just use 0 for the start thanks guys
     
  14. Nov 10, 2007 #13
    ok lol..
     
  15. Nov 10, 2007 #14

    Shooting Star

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    Hey bigtymer8700, you didn't put the D in the right place in your first post! Glad that you've understood.
     
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