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Homework Help: Momentum and Impulse on a car

  1. Mar 8, 2009 #1
    1. The problem statement, all variables and given/known data
    A 7.0 kg toy car can move along an x axis; Figure gives Fx of the force acting on the car, which begins at rest at time t=0. The scale on the Fx axis is set by Fxs = 6.0 N. In unit-vector notation, what is p at (a)t = 1.0 s and (b)t = 6.0 s,(c) what is v at t = 9.0 s?


    2. Relevant equations
    p = mv
    F = ma
    J = Ft
    V2 = v1 + at

    3. The attempt at a solution

    I tried solving for V2 using F = ma
    f = m(v2-v1/t)
    6 = 7 (v2 - 0/1)

    then i plugged this value into p = mv but then i realized they want unit vector notation and I got really confused! =S
  2. jcsd
  3. Mar 8, 2009 #2


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    Difficult to tell what is going on without the diagram.
  4. Mar 8, 2009 #3


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    You are dealing with a force that is not constant. The easiest way to deal with this is to remember the change in momentum is equal the the integral of the force with respect to time. I.e. the area under your force curve.
  5. Mar 8, 2009 #4


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    I see a diagram. Sometimes. It does seem to come and go. When I first open the page it's there. If I refresh the page it disappears. I'm using Firefox on Ubuntu. Hmm. Now it seems to be gone completely. Too bad. It was a nice diagram.
    Last edited: Mar 8, 2009
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