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Homework Help: Basic Acceleration Problem

  1. Sep 21, 2009 #1


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    Gold Member

    1. The problem statement, all variables and given/known data
    A car is traveling along a straight road at a velocity of +38.0 m/s when its engine cuts out. For the next ten seconds, the car slows down, and its average acceleration is a1. For the next five seconds, the car slows down further, and its average acceleration is a2. The velocity of the car at the end of the fifteen-second period is +22.6 m/s. The ratio of the average acceleration values is a1/a2 = 1.53. Find the velocity of the car at the end of the initial ten-second interval.

    2. Relevant equations
    Well, perhaps v = v0 + at has something to do with this.

    3. The attempt at a solution
    Unfortunately, as simple as it sounds, I'm somewhat stumped. What I don't understand is where the ratio comes into play, and how to combine all of this information in an equation. If somebody could point me in the right direction, I'll try to solve this problem on the forum before asking for a solution.

    Thank you very much for any assistance!
  2. jcsd
  3. Sep 21, 2009 #2


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    well if a =(v-u)/t

    Now a1= (v1-38)/10

    for a2, the initial velocity is v1 and the final is 22.6.

    You can now easily find what a1/a2 is using these equations and set that equal to 1.53 and get v1
  4. Sep 21, 2009 #3


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    Oh... that makes sense. ;-)

    So, in summary:

    ((v1-38)/10)/((22.6-v1)/5)=1.53, v1=26.393

    Thank you!
    Last edited: Sep 21, 2009
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