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Homework Help: Two trains travel. Based on their leghths, mesure

  1. Oct 19, 2011 #1
    1. The problem statement, all variables and given/known data
    Two trains trqvel on Paralel tracks in the same direction. Train 'A' has a length of 1 km and traveling at 50 m / s. Train 'B' has a length of 0.5 km and starts at just the moment when the rear of the train 'A' passes at the front of the train 'B'. Train 'B' has an acceleration of 3 m / s ^ 2 and a maximum speed of 60 m / s.

    a) At what instant does train B pass train A, that is to say at what point does the back of train 'B' pass the front of train 'A'?

    b) How far did train 'A' travel during that time?

    2. Relevant equations
    I've got:
    V= V0 + at
    x= x0 +(0,5)t^2

    3. The attempt at a solution
    I converted the lengths from km to m.

    Then, tried combining the equations, but i wind up with unknowns that i dont know what to do with.. Help me get started? Please!
    Last edited: Oct 19, 2011
  2. jcsd
  3. Oct 20, 2011 #2


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    Homework Helper
    Gold Member

    You would help yourself greatly if you could draw a distance versus time graph for the two trains. At least this will help you visualize what is going on. Suggestion: have one curve represent the location of the back-end of train A vs time, and the other curve represent the location of the front-end of train B vs time. This way the 2 curves can both start at the origin. A couple intermediate things you should determine that will help with the graph: How long will it take for the train B to reach its maximum speed? And, at that time, how far will the front-end of train B have traveled?
    Last edited: Oct 20, 2011
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