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Homework Help: Basic Momentum and Energy

  1. Dec 9, 2009 #1
    Basic Momentum and Energy!!

    Note: Take East as the positive direction. A(n) 88 kg fisherman jumps from a dock
    into a 123 kg rowboat at rest on theWest side of the dock.
    If the velocity of the fisherman is 4.1 m/s to the West as he leaves the dock, what is the
    final velocity of the fisherman and the boat?
    Answer in units of m/s.

    so do i just do 88 times 4.1 and get 36.08
    then do (88+123)v and get 211v
    then do 36.08=211v and solve for v??
     
  2. jcsd
  3. Dec 9, 2009 #2

    ideasrule

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    Re: Basic Momentum and Energy!!

    Yes, because initial momentum = 88*4.1 and final momentum=(88+123)v.
     
  4. Dec 9, 2009 #3
    Re: Basic Momentum and Energy!!

    no because i did that and got 360.8 = 211V
    then i solved for v and got 1.709952607 and it said i got it wrong.
    did i do anything wrong?
     
  5. Dec 9, 2009 #4
    Re: Basic Momentum and Energy!!

    Look at what direction is positive. You solved correctly

    The answer would be -1.71m/s
     
  6. Dec 9, 2009 #5
    Re: Basic Momentum and Energy!!

    -? why negative??
     
  7. Dec 9, 2009 #6

    ideasrule

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    Re: Basic Momentum and Energy!!

    Right, trick question! "Note: Take East as the positive direction."
     
  8. Dec 9, 2009 #7
    Re: Basic Momentum and Energy!!

    ohh!! gotcha!
    thank you very much!!
     
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