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Homework Help: How far did the car travel in the fourth second?

  1. Jun 2, 2010 #1
    1. The problem statement, all variables and given/known data
    A car accelerates from 14 m/s to 26m/s in 4s. How far did the car travel in the fourth second?


    2. Relevant equations
    a=vf-vi/t = 26-14/4=3

    d=vf^2-vi^2/2a=26^2-14^2/3=80


    The answer is 24.5, but I keep getting 80 and I don't know why.
     
  2. jcsd
  3. Jun 2, 2010 #2

    rock.freak667

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    Homework Helper

    Re: kinematics

    Your answer is correct, perhaps the book is wrong?
     
  4. Jun 2, 2010 #3
    Re: kinematics

    You've worked out the distance travelled in four seconds, the question is asking for the distance travelled in the fourth second.

    If you're still stuck;

    Try using the equation d = vi * t + (0.5 * a * t2)
    Use it to work out how far the car travels in three seconds, then how far it travels in four seconds (your value of 80m is correct).
    Then use the two to work out how far it travelled in the fourth second.
     
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