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Find the speed of the train.

  1. Sep 19, 2015 #1
    1. The problem statement, all variables and given/known data
    A train is at 0 m/s at the begining. It accelerates on a distance of 60 m, after it goes on a constant speed on the next 120 m and it finally decelerates on the next on 30 m and stops. The whole traject is 25 sec. Find the constant speed.

    2. Relevant equations

    x final = x initial + v initial * t + 1/2 * a * t^2
    3. The attempt at a solution

    60 = 0 + 0 + 1/2* a* t^2

    60 = 1/2 * a * t^2

    We also know that the first traject goes from 0 to 60 m and from 60 to 180 m and finally from 180 to 210 m.
     
  2. jcsd
  3. Sep 19, 2015 #2

    SteamKing

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    Writing down a couple of equations is not a valid attempt at solution. For this problem, you must examine all the parts of the trip in order to determine the constant speed of the train.
     
  4. Sep 19, 2015 #3
    Yeah I know but I have no idea on what to do next.... I wrote down 3 equations for each part of the traject but after that I have no idea...
     
  5. Sep 19, 2015 #4

    SteamKing

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    You wrote down an equation covering the first part of the trip. Don't you think you should write some additional equations describing the other parts of the same trip?
     
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