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Train force physics problem

  1. Jun 16, 2010 #1
    1. The problem statement, all variables and given/known data
    A freight train has a mass of 1.4x107 kg. If the locomotive can exert a constant pull of 6.7x105 N, how long does it take to increase the speed of the train from rest to 84 km/h?


    2. Relevant equations
    F=ma
    a=v/t


    3. The attempt at a solution
    I converted 84 km/h into 23.3 m/s.
    F=ma
    6.7x10^5 N=1.4x10^7 m (a)
    a= .047 m/s^2

    a=v/t
    .047 m/s^2=(23.3 m/s)/t
    t=495.7s --> 2.97x10^4 min
     
    Last edited: Jun 16, 2010
  2. jcsd
  3. Jun 16, 2010 #2

    rock.freak667

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    Homework Helper

    Re: Force

    That looks correct.
     
  4. Jun 16, 2010 #3
    Re: Force

    when I enter it it says that it differs significantly from the correct answer
     
  5. Jun 16, 2010 #4

    rock.freak667

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    Homework Helper

    Re: Force

    the t =2.97x104 min is not correct.

    t= 495.7 s should be correct.
     
  6. Jun 16, 2010 #5
    Re: Force

    the question asks for time in minutes
     
  7. Jun 16, 2010 #6
    Re: Force

    i converted it and got 8.26 min and got it correct.i don't know what i was thinking converting it before haha thanks
     
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