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Homework Help: Using acceleration to find distance traveled

  1. Oct 2, 2008 #1
    1. The problem statement, all variables and given/known data
    A car accelerates from 18 m/s to 45 m/s in 12 s. Assume constant acceleration.
    What was its acceleration? How far did it travel?

    I know that the acceleration is 2.25 m/s/s but I'm not sure how to go from acceleration to distance traveled.


    2. Relevant equations
    I'm guessing that its this one
    vf^2 = vi^2 + 2a * ChangePosition

    3. The attempt at a solution

    (vf^2 - vi^2)/2a = change in position

    So I get 45^2 - 18^2 / 24 which equals 70.875 meters. When I submitted the problem I got the acceleration right but I screwed up the change in position.
     
  2. jcsd
  3. Oct 2, 2008 #2
    d = 1/2 at^2
     
  4. Oct 3, 2008 #3

    Mentallic

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    Homework Helper

    You accidentally substituted the time instead of the acceleration into your rearranged equation:

    [tex]\Delta x=\frac{v_{f}^{2}-v_{i}^{2}}{2a}[/tex]
     
  5. Oct 3, 2008 #4

    Mentallic

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    Homework Helper

    To use this formula, the entire equation will need to be put to use. i.e.

    [tex]s=ut+\frac{1}{2}at^{2}[/tex]
    s = displacement
    u = initial velocity
     
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