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LearningPhysics one last runner problem

  1. Sep 13, 2007 #1
    1. The problem statement, all variables and given/known data
    Runner A is initially 6.0km west of a flagpole and is running with a constant velocity of 8.4km/h east. Runner B is initially 4.3km east of flagpole and is running with a constant velocity of 7.1km/h west

    how far are the runners from the flagpole when their paths cross?

    3. The attempt at a solution

    so again the time for both are the same and the distance apart is 10.3 km
    do i solve for t since t is equal for both runners?
     
  2. jcsd
  3. Sep 13, 2007 #2

    learningphysics

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    Yes, t is equal... how do the distances the two runners travel relate?
     
  4. Sep 13, 2007 #3
    well since the time is equal then wouldnt the distance of runner A be 1.18309 times more than runner B???
     
  5. Sep 13, 2007 #4

    learningphysics

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    Yes, but you don't really need that relationship... how does the 10.3km come into play here?
     
  6. Sep 13, 2007 #5
    im not sure how that comes into play since its where do they intersect
     
  7. Sep 13, 2007 #6

    learningphysics

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    draw a sketch... they start at 10.3km apart... they run towards each other... draw a line for the path one runner travels... draw a line for the other...

    what is the relationship between the length of the two lines?
     
  8. Sep 13, 2007 #7
    i see that they intersect i jsut dont know what formula or what i try and solve for to get this problem
     
  9. Sep 13, 2007 #8

    learningphysics

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    Well, I was getting at... the distance travelled by one runner + distance travelled by the other = 10.3 km
     
  10. Sep 13, 2007 #9
    ahhhhh damn i knew that ... i thought u meant something more complex... its gettin late here and im bucklin down to finsih this last one
     
  11. Sep 13, 2007 #10
    so if the Time is equal and the Distance is D of 1 + D of 2 = 10.3 how do i solve for that?
     
  12. Sep 13, 2007 #11
    do i get 8.4t + 7.1t = 10.3 km?

    which give me a time of intersect at .6645 hours?
     
  13. Sep 13, 2007 #12

    learningphysics

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    yup. how far are they from the flagpole.
     
  14. Sep 13, 2007 #13
    so after that time runner A has gone 5.581935484 km and he was initially 6km away

    so he is now .4180645161 km away from the pole
     
  15. Sep 13, 2007 #14
    AWESOME THAT WAS CORRECT

    YOU ARE THE MAN AND A SAVIOR.... this should be all my problems until next week... i was workin ahead to avoid them over the weekend
     
  16. Sep 13, 2007 #15

    learningphysics

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    cool. :smile: no prob.
     
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