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Homework Help: Locomotive, friction, and speed question

  1. Feb 28, 2009 #1
    1. The problem statement, all variables and given/known data

    A 4.6×104 kg locomotive, with steel wheels, is traveling at 14 m/s on steel rails when its engine and brakes both fail. The coefficient of friction is 1.6×10−3.

    1.) How far will the locomotive roll before it comes to a stop?

    Answer in meters using two significant figures.

    2. Relevant equations

    3. The attempt at a solution

    I tried to do something here and I thought I had the solution but it was wrong. Please check my work and help me understand this problem.

    Here is what I did:

    1.6*10^-3 x4.6 *10^4 x9.8 =721 N

    -721.28/1.6*10^-3 = -450800 m/s^2

    v2-u2/2a ----> 0-14^2/2*-450800 ---> -196/-901600

    d=2.17*10 ^-4
  2. jcsd
  3. Feb 28, 2009 #2


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    Science Advisor
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    Gold Member

    Your second equation makes no sense with the units. What equation are you trying to use for step 2?
  4. Feb 28, 2009 #3
    Honestly, I had no idea what I was doing. I tried looking at how someone solved the same problem with different numbers and just plugged my numbers in but it didn't work.
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