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Angular acceleration from angular velocity

  1. Mar 17, 2016 #1
    Hello everybody. I would really appreciate some help
    1. The problem statement, all variables and given/known data
    I have some problem where I have measured angular velocity data. This measurements are not equally spaced, meaning there were taken after some (variable) delay passed.

    I need to find what is the angular acceleration at each point of measurement.

    2. Relevant equations

    ummmm I don't know... perhaps α= Δω/Δt??

    3. The attempt at a solution

    So I have some measures like

    Code (Text):

    Time(μs)    Speed(rad/s)           Accel(rad/s^2)
    ------------------------------------------------------------
    15115        2.078458          
    24184       3.464097                  91.67310552 ???????
    31238       4.453629
    37207        5.263176
    42474        5.964667
     
    My question is how to fill the Acceleration values....

    I have tried accel=(speed2-speed1)/(time2-time1) (see the 91.67310552)

    Is this flawed??

    The graphic of the speed show a almost linear increase of speed (until it becomes constant), so by theory this should give a constant acceleration and then 0 right? But my calculations become kind of crazy after a whileand give a zigzag curve after a promising start...

    so can anyone check if my ideas are ok?

    thanks
     
  2. jcsd
  3. Mar 17, 2016 #2

    andrewkirk

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    That's a fine way to do it. But you seem to have done the calc wrong. I get 153, not 91.7.
    You can calculate four angular acceleration values from your data, and they make a nice smooth progression, with a slight, gradual decline from the original value, which seems realistic.
     
  4. Mar 17, 2016 #3
    Thank you very much for your reply.
    Yeah I realized my calculation mistake. Thanks.
    I did the calculations for all the data and I got the following graphs
    speedaccel.jpg

    Well although the speed graphs seems quite nice, the acceleration graphs have some ups and downs. I suppose physical systems are not the same as theory so instead of the square curve I was expecting I got that. Seems close enough I guess..

    Thanks again for the help. It is very appreciated. It has been years since I took physics and frankly I remember very few... :frown:
     
  5. Mar 17, 2016 #4

    haruspex

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    The zigzags suggest rounding error. Can you post the data for that part?
     
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