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Conservation of Momentum/Linear Momentum

  1. Feb 27, 2007 #1


    2. Relevant equations

    Pi = Pf

    3. The attempt at a solution

    v=-1.3 m/s

    But this is the wrong answer...what am I doing wrong???
  2. jcsd
  3. Feb 27, 2007 #2


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    Homework Helper

    firstly, weights were given in Newton already, no needs to add an extra "g". secondly, if you do want to use momentum (somehow), you want the "mass" of the objects.
  4. Feb 27, 2007 #3
    usually i get ma equations in variables n thn substitute the values.........suppose the man moves at a speed w towards left and the platform recoils at a speed V towards right...hence the speed of the man relative to the platform is V+w=v...or w= v-V....
  5. Feb 27, 2007 #4
    taking the man n the platform to b inna system, there is no external horizontal force on the system, the linear momentum remians constant. thus
    (M+m)18 = MV- mv...now solve n check
  6. Feb 27, 2007 #5
    sorry, the eqn above shud hav been (M+m)18 = MV- mw
  7. Feb 27, 2007 #6
    ooookay...the catch is , it will recoil wit V+18 and not just V....ill just try n let u know
  8. Feb 27, 2007 #7
    If You look at what I posted above that is the equation that I used and it did not work...(M+m)18=M(v+18)+m(v+18) and it did not give me the right answer.

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