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Runner A and Runner B

  1. Sep 2, 2009 #1
    Runner A is initially 5.6 km west of a flagpole
    and is running with a constant velocity of
    8.7 km/h due east. Runner B is initially 4.2
    km east of the flagpole and is running with a
    constant velocity of 7.4 km/h due west.

    How far are the runners from the flagpole
    when their paths cross? Answer in units of
    km.


    How do i even start this, im stuck.
     
  2. jcsd
  3. Sep 2, 2009 #2
    Drawing the scenario is always a good place to start.
    R1------------------------------F-------------------------R2
    Now you're looking for when R1 and R2 pass each other. That means what?
     
  4. Sep 2, 2009 #3
    displacement by chance?
     
  5. Sep 2, 2009 #4
    Like i drew it out, but when i do i still dont know how to set it all up. Im so stumped. :(
     
  6. Sep 2, 2009 #5
    I got .3 KM but it says its wrong.. ugh
     
  7. Sep 2, 2009 #6
    The runners will pass each other. This would happen after t hours. So that means that after t hours both runners will be at the same spot (not the same distance ran).
    -Basically, at some time t, the two runners x position will be equal.
     
  8. Sep 2, 2009 #7
    8.7 km/h + 7.4 km/h = 4.7 km + 5.6 km

    16.1 km/h = 9.8 km

    t = 9.8 km / 16.1

    t=.608695652

    8.7 * .608695652 = 5.29565213

    5.6 - 5.29565213 = .30434782

    your answer is .30434782 buddy
     
  9. Sep 2, 2009 #8
    Hm, confusing. lol. I set it up and got 5.29 but ugh wouldnt it be .31
     
  10. Sep 2, 2009 #9
    Why don't you post what you did.
     
  11. Sep 2, 2009 #10
    Ugh it wanted the full number, thanks ~.~
     
  12. Sep 2, 2009 #11
    it was operator and stupid website error lol
     
  13. Sep 2, 2009 #12
    happens..i had trouble on this one early tonight but i figured it out..
     
  14. Sep 2, 2009 #13
    well thanks man, heh.
     
  15. Sep 2, 2009 #14
    no prob.
     
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