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Homework Help: Rate Of Current

  1. Oct 12, 2007 #1
    1. The problem statement, all variables and given/known data
    A canoist is rowing upstream a river. After 2miles he passes a log (traveling with the current) he continues to row for one more hour and turns around. He reaches his starting point at the same time as the log. What is the rate of the current?

    2. Relevant equations

    3. The attempt at a solution
    To be honest I don't even know where to begin with this problem. The teacher gave it to us as a joke because he said this was something from his highschool book in Russia and hasn't found anyone in the U.S who can solve it.
    Last edited: Oct 12, 2007
  2. jcsd
  3. Oct 12, 2007 #2


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    Homework Helper

    Draw a picture.

    the start point = 0---------------- log position= 2miles ------------- turnaround point

    So suppose the current's speed is c.

    What is the position of the turnaround point in terms of c?

    Where is the log located when the rower reaches the turnaround point?
  4. Oct 13, 2007 #3


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    Staff Emeritus
    Science Advisor

    Assume that the speed v of the canoist (with respect to current) is constant, or the average speed is constant for the different phases of the trip. The current's speed is constant c.

    Traveling upstream, the distance traveled is (v-c)*t, and down stream the effective speed is v+c. Knowing the times and distances, one should be able to find two equations to solve to the two unknowns, v and c.
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