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Homework Help: Deriving a common formula

  1. Jul 6, 2009 #1
    1. The problem statement, all variables and given/known data

    See the attachment please.

    3. The attempt at a solution

    I know the v1 x delta (t) is for the rectangle,
    I dont see how the second part works? I dont understand why the t^2 and how a replaces the area formula i have written.

    Thanks for your help, its my first day of class today, and its been a while since i was last in a physics / math class.

    EDIT: I added a formula sheet we were given, sorry i just dont see the relationship right now..

    Attached Files:

    Last edited: Jul 6, 2009
  2. jcsd
  3. Jul 7, 2009 #2


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    Homework Helper

    You can replace [itex]\Delta v = v_2 - v_1[/itex] by the acceleration a. In the picture, the acceleration is the slope of the line, algebraically it is given by
    [tex]a = \frac{\Delta v}{\Delta t}[/tex].

    So just write down the area of the triangle and do the substitution.
  4. Jul 7, 2009 #3
    from the second equation on the formula sheet,

    from the graph, d=vit+[tex]\frac{1}{2}[/tex](vf-vi)*t
    therefore, d=vit+[tex]\frac{1}{2}[/tex]at2
    (since vf-vi=at)
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