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Momentom question. But Hard one:O

  1. Mar 26, 2009 #1
    1. The problem statement, all variables and given/known data
    The only force acting on a 2 kg object moving along the x axis is shown. If the velocity Vx is 2 m/s at t=0, what is the velociity at t=4 s ?


    2. Relevant equations
    P= mv


    3. The attempt at a solution
    Area under the curve is the Impulse, which is Pf - Pi and it's equal to 4
    That indicates that p at t=4 - p at t=0 = 4

    However, given that v at =0 is 2
    By the sub. of the formula we get that P at t=0 is 4 and therefore P at t=4 is 0

    Is that Correct ?
     
  2. jcsd
  3. Mar 26, 2009 #2

    rl.bhat

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    Homework Helper

    By the sub. of the formula we get that P at t=0 is 4 and therefore P at t=4 is 0

    No. P at t=4 becomes 8
     
  4. Mar 27, 2009 #3
    Ya, that's ubsolutly right. But what confuses me is that it is a multiple choise ques.

    And the choises are
    4
    5
    6
    7
    2
    There isn't any 8 ??
     
  5. Mar 27, 2009 #4

    rl.bhat

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    You have to post the figure or graph whichever is given in the problem.
     
  6. Mar 27, 2009 #5
    Okay, I might just be very, very confused but:

    I = Pf - Pi = mvf - mvi

    I/m = vf - vi

    vf = vi + ( I/m )

    You say vi = 2, I = 4 & m = 2

    Then vf = 2 + (4/2) = 4 ?

    So yes p(4) = 8, but p=mv & you want to find v..
     
  7. Mar 27, 2009 #6
    Uha ,

    That's right..

    Then the velocity becomes 4 ..

    Thanks
     
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