1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Marathon runner velocity Date
[SR] Relativistic runner and two relativistinc trains... Jul 15, 2017
Runner Runs Sep 14, 2016
Runner on a turntable Apr 9, 2016
Marathon Runner Weight? Jan 22, 2005