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Homework Help: Potential Energy and Kinetic Energy Question

  1. Feb 28, 2009 #1
    1. The problem statement, all variables and given/known data
    A bird is flying with a speed of 17.4 m/s over
    water when it accidentally drops a 2.20 kg
    fish.
    The acceleration of gravity is 9.81 m/s2 .
    If the altitude of the bird is 7.70 m and air
    resistance is disregarded, what is the speed of
    the fish when it hits the water? Answer in
    units of m/s.


    2. Relevant equations
    i tried to do potential energy equation PEg=mgh and then since it is converted to KE i re- arange the equation KE=1/2mv^2 and i tried it and it was wrong

    3. The attempt at a solution[/b
     
  2. jcsd
  3. Feb 28, 2009 #2

    Doc Al

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    Staff: Mentor

    The change in PE will tell you the change in KE. Don't forget that the fish already had KE when it was released.
     
  4. Feb 28, 2009 #3
    so i have to add the KE of bird and PE of the fish
    then use the KE=1/2MV^2
     
  5. Feb 28, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Add the initial KE of the fish. (How fast is the fish moving when it's released?)
     
  6. Feb 28, 2009 #5
    thanks a lot,i got it rite this time
     
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