1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find the trajectory of a boat that moves in a river

  1. Feb 13, 2014 #1
    1. The problem statement, all variables and given/known data
    A boat part from the point P of the bank of a river, with width D, and that flows with a constant velocity VR, and moves with a constant velocity VB, directed towars a point Q, located on the other side of the river directly in front of P. If r is the instantaneous distance of the boat respect to Q and θ is the instantaneous angle between r and PQ, show that the trajectory of the boat is determined by:

    r=Dsecθ/(secθ+tanθ)VB/VR

    2. Relevant equations



    3. The attempt at a solution
    I am completely lost in this problem; I to put the instantaneous distance of the boat r as a vector and a took Q as my origin r = cos(90-θ)i+sen(90-θ)j but then i dont know what else to do; I would appreciate your help a lot
     
  2. jcsd
  3. Feb 14, 2014 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Have you copied the problem text correctly? "A boat part from the point P of the bank of a river, with width D, and that flows with a constant velocity VR, and moves with a constant velocity VB, directed towars a point Q, located on the other side of the river directly in front of P." If the boat moves with constant velocity it never reaches point Q. Was not it constant speed with respect to the river?

    You are right, treat the position and velocity of the boat as vectors. The velocity of the boat with respect to the river points towards Q. What is the velocity of the boat with respect to the shore?

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Find the trajectory of a boat that moves in a river
  1. River Boat (Replies: 6)

  2. Boat going up a river (Replies: 2)

Loading...