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Average velocity and average speed problem.

  1. Aug 28, 2008 #1
    1. The problem statement, all variables and given/known data
    Compute your average velocity in the following 2 cases: (a): You walk 73.2 m at a speed of 1.22 m/s and then run 73.2 m at a speed of 3.005 m/s along a straight line.


    2. Relevant equations
    this asks for average velocity which equals=change of x/change of t or xfinal-xinitial/tfinal-tinitial


    isn't acceleration = change of velocity over/ change of time

    so what do i do, because it gives me two velocities
     
  2. jcsd
  3. Aug 28, 2008 #2

    LowlyPion

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    How long did it take you to accomplish the circuit? Vavg is defined as what? You know change of x, so ...?
     
  4. Aug 28, 2008 #3
    Ok. I'm assuming that you add both of the velocities. 1.22 m/s+ 3.05 m/s=4.27m/s
    My total distance was 73.2 m + 73.2 m=146.6 m

    4.27m/s / 146.6 m=.0291268759 seconds
     
  5. Aug 28, 2008 #4

    LowlyPion

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    I think you've used an invalid approach.

    The sum of the velocities divided by the total distance is not equal to the time.

    How long does it take to do the first leg - 73.2 m at 1.22 m/s?
     
  6. Aug 28, 2008 #5
    It takes 60 seconds.
     
  7. Aug 28, 2008 #6

    LowlyPion

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    OK. Now how long for the second leg?
     
  8. Aug 28, 2008 #7
    It takes 24 seconds
     
  9. Aug 28, 2008 #8

    LowlyPion

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    Knowing total distance and total time now you are in position to calculate avg velocity. This is given by which of the equations you cited in your first post?
     
  10. Aug 28, 2008 #9
    ok so it would be 73.2+73.2=146.4

    146.4m/60s-24s=4.07m/s
     
  11. Aug 28, 2008 #10
    wait a minute would i add the time together
     
  12. Aug 28, 2008 #11

    LowlyPion

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    Well I sure would. Not sure why you would subtract time in this case. You want total time.

    You did post this didn't you?
     
  13. Aug 28, 2008 #12
    oh yeah huh.
     
  14. Aug 28, 2008 #13
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