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River Relative Velocity

  1. Feb 22, 2013 #1
    1. The problem statement, all variables and given/known data
    Two students are canoeing on a river. While heading upstream, they accidentally drop an empty bottle overboard. They then continue paddling for 1 h, reaching a point 2 Km farther upstream. At this point they realize that the bottle is missing and, driven by ecological awareness, they turn around and head downstream. They catch up with and retrieve the bottle (which has been moving along with the current) 5 Km downstream from the turn-around point.

    I am wondering if the setup in my picture is correct. I have my work on there.


    2. Relevant equations



    3. The attempt at a solution

    Vc/w = velocity of the canoe relative to the water.
    Vc/e= velocity of the canoe relative to the earth.
    Vw/e= velocity of the water relative to the earth.

    Vc/e=Vc/w + Vw/e
     
    Last edited: Feb 22, 2013
  2. jcsd
  3. Feb 22, 2013 #2

    mfb

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    There is an easy way to get t2 without any calculation. This allows to get the river velocity quickly, and afterwards the problem is easy to solve.

    I disagree with your equations V1=Vc/w and V2=Vc/w. The 2 and 5km refer to earth.
     
  4. Feb 22, 2013 #3
    Yeah I messed up. How would you go about getting the time without calculations? By the way I got it.
     
    Last edited: Feb 22, 2013
  5. Feb 22, 2013 #4

    mfb

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    Staff: Mentor

    Consider the problem in the frame of the bottle.
     
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