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Homework Help: Acceleration/distance problem

  1. Feb 3, 2009 #1
    1. The problem statement, all variables and given/known data
    In the 100 m dash a sprinter accelerates from rest to a top speed with an acceleration whose magnitude is 2.68 m/s2. After reaching top speed, he runs remainder of race with constant velocity. If total race is run in 12.0s, how far does he run during the acceleration phase?

    2. Relevant equations
    d1= 1/2*2.68 m/s2*t2
    d2= vt = 2.68 m/s2*t*12.0s - t

    3. The attempt at a solution
    Not knowing if the above equations are correct I tried d1+d2=100m.
    I multiplied everything, moved the 100m to the other side and tried the quadratic formula. I don't think I came out with the correct answer. I got approx. t= 3.5 or t= about 18. Any suggestions
  2. jcsd
  3. Feb 3, 2009 #2
    Nevermind. I've finally figured out my errors.
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