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Homework Help: Motion in one dimension- Find acceleration and original velocity

  1. Sep 11, 2008 #1

    Xen

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    1. The problem statement, all variables and given/known data
    A truck covers 40.0m in 8.50s while smoothly slowing down to a final velocity of 2.8 m/s. a) Find the truck's original speed b) Find its acceleration


    2. Relevant equations
    a= [v-vo]/t-to

    Constant acceleration:
    v=vo + at
    x= xo + vot + (1/2)at2

    Constant velocity:
    x=vt +xo


    3. The attempt at a solution

    well i've made pages of attempts in my notebook...but here's a sample of what i've tried

    2.8 m/s = Vo + [ (2.8 m/s)2 - Vo2 / 80 ]* (8.50)

    2.8 m/s = Vo + 66.64/80 - (8.50Vo2)/80
     
  2. jcsd
  3. Sep 11, 2008 #2

    Kurdt

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    You have a quadratic equation in the initial speed. How would you solve a quadratic equation.
     
  4. Sep 11, 2008 #3

    Xen

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    Set it equal to zero then use the quadratic formula which would give the initial speed?
     
  5. Sep 11, 2008 #4

    Kurdt

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    Yes, that is how you would solve for the initial velocity.
     
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