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Homework Help: Motion problem

  1. May 9, 2006 #1
    I was wondering if someone could check my work and see if its correct.

    An object of mass 100.00kg moves in a straight line under the influence of a force given by F(t)=(120 N/s)t+4000N
    At t=0 it is moving at 0 m/s. Determine its speed at t=5.00 s

    What i did is this. I plugged 5s into the function and got 4600N. Then i used F▲V=M▲V arranged to V=(F▲T)/M
    V=(4600N X 5.00s)/100.0kg
    V=230. M/S

    Thank you
  2. jcsd
  3. May 9, 2006 #2


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    [tex] \int_{0}^{5} (120t + 4000)dt = m \int_{0}^{v} dv [/tex]
  4. May 9, 2006 #3


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    I hope that you meant F ▲t = m ▲v ... which DOES lead to ▲V = (F▲t)/m .
    . . . ("change" symbols in an equation should ALWAYS balance) . . .

    But why would you use the strongest Force in the 5-second duration?
    Why not use the weakest Force, instead? . . . why not use the AVERAGE ?
    . . . (ALWAYS multiply one's full range by the other's average) . . .
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