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Finding speed and distance of a train

  1. Jan 27, 2013 #1
    1. The problem statement, all variables and given/known data

    A train has a mass of 5.77E+6 kg and is moving at 99.4 km/hr. The engineer applies the brakes, which results in a net backward force of 1.11E+6 N on the train. The brakes are held on for 26.9 s.

    What is the new speed of the train?

    How far does it travel during this period?

    mass of train: 5,770,000 kg

    speed of train: 99.4 km/hr (i converted it to m/s and got 27.611 m/s)

    Backwards net force of: 1,110,000 N

    Brakes held for: 26.9 s

    2. Relevant equations

    f=ma?

    V=Vo+at?

    X=Xo+(Vo)(t)+.5at^2?

    3. The attempt at a solution

    I am fairly new to physics and don't really know what I'm doing, anyways...first i used f=ma
    and got a=.192 then i used that in the second equation and got V=1,110,005.165 N and then I plugged that into the third equation and got 29859069.4666 M but it said i was wrong :/.

    Can someone please guide me through this problem? it would be much appreciated

    -Thanks in advance!

    Ok, so i tried it again and i was confident that i was correct.

    i used f=ma to get a=.192

    i then used a in the second equation ( V=27.611+.192(26.9)) to get a Velocity of 32.7758

    i then used the 3rd equation to get a distance of 812.20246 m but it said it was wrong again.

    can you help me clarify or show me where i went wrong?

    Thanks
     
  2. jcsd
  3. Jan 27, 2013 #2

    micromass

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