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Homework Help: Force and Motion .

  1. Sep 30, 2004 #1
    Force and Motion.....

    could someone please tell me where i am going wrong with this question:
    A freight train has a mass of 1.20E+7 kg. If the locomotive can exert a constant pull of 6.10E+5 N, how long does it take to increase the speed of the train from rest to 83.4 km/hr?
    i tried to find accelertion by using F=ma, and i keep getting 0.05833....then i put it into the equation v=vo+at, but my answers never turn out right. i think maybe unit conversion is where i'm going wrong.....but i'm not sure.
    help would be appreciated...
    thanks, lilly
  2. jcsd
  3. Sep 30, 2004 #2

    Doc Al

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    Staff: Mentor

    Right method. I assume that's a typo, since I get 0.050833 m/s^2.
    Sounds good to me. If you aren't sure of your conversion, show how you did it.
  4. Sep 30, 2004 #3
    I think this would help

    My Acceleration is 0.0508333
    83.4 KM/Hr = 83.4 * 5/18 m/sec = 23.16 m/sec which is the final velocity.
    So according to the formula you used, u = uo + at my value for t turns out to be 23.16/0.0508333 = 455.6 seconds.
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