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Angular velocity

  1. Aug 22, 2008 #1
    1. The problem statement, all variables and given/known data

    The following data are for the angular displacement of the knee in cycling
    measured in degrees. Using radian measure, compute the angular velocity
    and acceleration when the knee angle is 119.1 degrees. The sampling
    frequency was 50 Hz. What is a problem you may encounter when calculating
    higher derivatives from sampled displacement data?
    98.0, 103.5, 109.0, 114.2, 119.1, 123.4, 126.9


    2. Relevant equations

    Angular velocity is degrees per unit time.


    3. The attempt at a solution

    I only have the angle. And a frequency but not a discrete time variable? Thanks!
     
  2. jcsd
  3. Aug 22, 2008 #2

    Hootenanny

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    What is the definition of frequency? :wink:
     
  4. Aug 23, 2008 #3
    Yeah I agree it is 50 cycles a second but then I'm not sure how to apply that?
     
  5. Aug 23, 2008 #4

    Hootenanny

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    So, you know that every second there are fifty measurements taken. Equally, you know that each measurement is separated by [itex]1/50 = 0.02[/itex] seconds.

    Can you go from here?
     
  6. Aug 25, 2008 #5
    Oh right you make it so simple! Thanks.

    So change in velocity over change in time. Change in time is 0.02sec

    change before
    119.1 -114.2 = 4.9deg
    4.9/0.02=245deg

    change after
    123.4 - 119.1 = 4.3deg
    4.3/0.02=215deg

    (245+215)/2= 230deg.sec-1

    Accel= change of rate of velocity is (230-245)/2
    =-1500ms-2
     
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