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Homework Help: Marathon runner velocity problem

  1. Sep 4, 2010 #1
    1. Consider a marathon of 42.195 kilometers. In order to attain the qualifying time of 3 hours and 15 minutes to enter the race, a runner would need to run at an average velocity (in m/s) of

    2. I thought this would be average speed = distance traveled/time interval spent traveling

    3. Since they wanted it in terms of m/s, I divided 42.195 by 1000. Then to get seconds, I converted 3 hr and 15 mins to 11700 seconds, which gives 3.6E-6.

    But apparently its wrong. Help?
  2. jcsd
  3. Sep 4, 2010 #2
    Re: Velocity...again

    Why did you divide by 1000?
  4. Sep 4, 2010 #3
    Re: Velocity...again

    To go from kilometers to meters
  5. Sep 4, 2010 #4
    Re: Velocity...again

    You are not canceling units correctly:

    [tex]1 km * 1000 \frac{m}{km} = 1000 m[/tex]
  6. Sep 4, 2010 #5
    Re: Velocity...again

    Ohhh, the right is answer is 3.6 then. Thanks! That makes more sense.
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