1. Limited time only! Sign up for a free 30min personal 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!

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

    User Avatar
    Homework Helper

    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

    User Avatar
    Homework Helper

    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!!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook