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Average velocity given acceleration and time?

  1. Oct 11, 2009 #1
    1. The problem statement, all variables and given/known data

    A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by x(t) = bt^2 - ct^3, where b = 2.30 m/s^2 and c = 0.120 m/s^3.

    (a) Find the average velocity of the car for the time interval t=0 to t=10 s

    (b) Calculate the instantaneous velocity of the car at t=0, t=5 s, and t=10 s

    2. Relevant equations

    Not sure...for the first one, I thought it might be simply v = x2-x1/t2-t1 but then I realized I was given acceleration rather than distance so that won't work. Will I have to use integrations?

    3. The attempt at a solution

    I have no idea how to start either of these, but I have a feeling I have to integrate them and I'm really confused on that concept. =\

    Thanks in advance,

    - Grace
  2. jcsd
  3. Oct 11, 2009 #2


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    What makes you say you are given acceleration?
  4. Oct 11, 2009 #3
    I said that because b and c are in m/s^2 and m/s^3, not meters...unless that doesn't matter? =\ But I see what you mean, it saying distance...
  5. Oct 11, 2009 #4


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    Yes, it says distance. If you look at the right side you multiply b(m/s2)*t2(s2) and you end up with meters. Same thing with c. This is dimensional analysis. I trust you know how to proceed from here.
  6. Oct 13, 2009 #5
    Oh wow, I can't believe I didn't see it before. Thanks so much for your help, it makes sense now...
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