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Adv. function work problem(polynomialf)

  1. Sep 15, 2011 #1
    1. The problem statement, all variables and given/known data


    Two soccer players start at opposite sides of an 80-m field. One runs at 4m/s and the other runs at 5m/s. If they run back and forth for 15 min how many times will they pass eachother?


    Does anyone know how to solve this?





    2. Relevant equations



    3. The attempt at a solution

    I tried this one, did 80/4 to get distance ran, then divided that by 900s to get amount of times ran from the track.

    900s / 20 laps is 45.

    I think thats right, buti dont know where to go from there. What do i do with the second runner? It doesnt work out, any hints, help etc.. plz very urgent
     
  2. jcsd
  3. Sep 15, 2011 #2
    any1?
     
  4. Sep 15, 2011 #3
    If the answer isn't readily apparent, draw a diagram. How many meters will the 4ms runner cover in 15 minutes? How many will the 5ms runner cover?

    Now plot the position of the two runners. For example, where are the two runners after 5 seconds? 6 seconds? 7? How about after 10 seconds? Have they passed each other yet? If so, at what time did they pass. Be specific.

    Then keep plotting until you discover the second instance of passing. Note the time it occurs. After 3 or 4 passings you'll see the pattern.

    Then the formula should become apparent.
     
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