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Swimming across a river

  1. Feb 2, 2010 #1
    1. The problem statement, all variables and given/known data
    A swimmer wants to cross a river, swimming directly from point A to point B, as shown in the figure. The distance d_1 (from A to C) is 185 m, the distance d_2 (from C to B) is 141 m, and the speed v_r of the current in the river is 5.00 km/h. Suppose that the swimmer's velocity relative to the water makes an angle of 36.0 degrees with the line from A to C, as indicated in the figure.

    1)What is the angle between the velocity vector for the swimmer with respect to a stationary observer (i.e. an observer standing at rest on the shore) and the riverbank?

    2)What is the angle between the velocity vector for the swimmer with respect to the water and the velocity vector for the swimmer with respect to a stationary observer?

    3)To swim directly from A to B, what speed u_s, relative to the water, should the swimmer have? Hint: use the law of sines with the known values in your velocity vector triangle.

    2. Relevant equations



    3. The attempt at a solution
    I havent got a clue other than possibly using related vectors to solve this problem, but i cant seem to get it to work, any help would be greatly appreciated
    thanks
     
  2. jcsd
  3. Feb 2, 2010 #2

    Delphi51

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    Homework Helper

    We need the diagram or at least an explanation of where A, B and C are located.
     
  4. Feb 2, 2010 #3
    Last edited by a moderator: May 4, 2017
  5. Feb 2, 2010 #4
    i am working on this same problem. i dont get it :(
     
  6. Feb 2, 2010 #5
    Yeah the wordings are weird.
     
  7. Feb 2, 2010 #6
    yeah mastering physics is stupid.
     
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