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Deisel train kinematics

  1. Nov 23, 2007 #1
    1. The problem statement, all variables and given/known data

    A deisel train accelerates uniformly from rest to reach 60km/hr in 6 minutes, after which the speed remains constant.
    Calculate the total time taken to travel 6km and the acceleration.

    2. Relevant equations
    s= ut
    v= u+at
    s=ut + 0.5*at^2

    3. The attempt at a solution
    I'm not sure how to incorporate the accelaration part into the question.
    I tried t=(v-u)/a but idon't know what to put in for the acceleration.
     
    Last edited: Nov 23, 2007
  2. jcsd
  3. Nov 23, 2007 #2
    That is not a question.
     
  4. Nov 23, 2007 #3
    yeah i accidentally entered the post before i finished it, it's finished now.
     
  5. Nov 23, 2007 #4
    Well the time taken to accelerate is 6min, because we are given that.

    First find the distance travelled in the 6mins it is accelerating.

    6mins = 1/10 hours. We must find the acceleration.

    Re-arrange v= u+at for acceleration:

    a = (v - u)/t = 60/(1/10) = 600 km/h^2

    Now find the distance it travels:

    s=ut + 0.5*at^2 = 0 + 0.5*600*(1/10)^2 = 3km

    Therefore the train still has 3km left to go, but now it is travelling at a constant 60km/h, so the time taken is:

    s = ut
    so:
    t = s/u = 3/60 = 1/20 of an hour = 3mins

    So the total time for the journey is 9mins
     
  6. Nov 23, 2007 #5
    thank you
     
  7. Nov 23, 2007 #6
    My Pleasure.
     
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