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Physics Energy Problem

  1. Jan 11, 2009 #1
    1. The problem statement, all variables and given/known data
    Vernie (mass of 50.0kg) needs to swing across a river to rescue George (mass of 80kg). She must swing into a constant horizontal wind force F ona vine that is initially at an angle of O with the verticle. The width of the river between them is 50.0m. The force of the wind blowing towards Vernie is 110N, and the length of the rope os 40.0m an dthe angle is 50 degrees.
    (a.)With what minimum speed must Venie begin her swing in order to just make to the other side.
    (b.) Once the rescue is complete, George and Vernie must swing back across the river, with what minimum speed must they begin their swing?


    2. L-(Lcos50 deg)
    KE(Kinetic Energy)=1/2mv2

    PE(Potential Energy)=mgh




    3. The attempt at a solution
    KE=PE
    1/2mv2=mgh

    V= sqrt 2gh
     
    Last edited: Jan 11, 2009
  2. jcsd
  3. Jan 11, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    A diagram would be helpful. (Where is the vine with respect to the river?)

    In setting up your energy balance equation, don't forget to include the work that must be done against the wind force.
     
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