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Maximum velocity problem

  1. Jan 7, 2017 #1
    1. The problem statement, all variables and given/known data
    A train travels a distance of 1,2 km between two stations with an average velocity of 43.2 km/h. During it's motion, at the time t1=40s it moved accelerated, then at time t2 it moved uniformly, then at t3=40s it moved uniformly slowed. Find the maximum velocity of the train.
    The acceleration during the slowed motion is equal in modulus to the acceleration during the accelerated motion.

    distance=1,2 km
    average velocity=43.2 km/h
    t1=40s
    t3=40s
    |a3|= a1

    Hopefully it makes sense.

    2. Relevant equations

    3. The attempt at a solution
    I tried solving it by finding the total time. Ttotal=average velocity/total distance. 1.2/43.2=0.027 h or 97.2 seconds

    from here i can find t2 which is 97.2-40-40=12.7
    after this i'm stuck and don't know what to do next.
     
  2. jcsd
  3. Jan 7, 2017 #2

    PeroK

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    You could try drawing a graph of velocity against time.
     
  4. Jan 7, 2017 #3
    How exactly can i draw a graph of velocity against time with all my known data?
     
  5. Jan 7, 2017 #4

    PeroK

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    What's the problem? It accelerates, it moves at constant speed for a time, then it decelerates to a stop. You can draw that.
     
  6. Jan 7, 2017 #5
    How do i draw a velocity against time graph?
     
  7. Jan 7, 2017 #6

    PeroK

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    You put time along the x-axis and velocity along the y-axis, then you draw the velocity as a function of time.

    You need to know that distance travelled is the area under the velocity-time graph.

    Do they not teach you this anymore?
     
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