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Steepest slope before slipping

  1. May 13, 2009 #1
    1. The problem statement, all variables and given/known data
    The coefficient of friction between the trains wheel's and the rail on a frosty day is 0.1, What is the steepest slope (expressed in the form ''1 in n'') that the train can climb without slipping.


    2. Relevant equations

    Ff = μ(Fn)

    3. The attempt at a solution

    I have no idea. Don't want a solution, just a little guidance would be much appreciated. I understand that the point where the train will begin to slip is when the maximum friction force is reached but I can't see how to apply this to this question.
  2. jcsd
  3. May 13, 2009 #2


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    OK. You've got the force of friction.

    If it's on an incline what force must it at least match in order to go uphill?
  4. May 13, 2009 #3
    The force must be at least equal to the natural force. what I've attempted so far, I found the frictional angle to be 5.71o, by tan-1(0.1*N/N). now i'm lost.
  5. May 13, 2009 #4


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    The statement says:
    Maybe they just want it as a 1 in 10 rise or more precisely as a rise of 1 /(102 + 1)1/2 = 1 in 10.05 rise?
  6. May 13, 2009 #5
    That would make sense, as the answer I think is 57o, but just out of curiosity how did u come to that conclusion, as it is not in the question do u just have to assume this. Freshmen to physics so excuse my ignorance if i am missing something obvious. Thanks for your help by the way.
  7. May 13, 2009 #6


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    Your 5.7° answer is correct of course. I was merely noting the form that they want the answer in.

    Physics is also a matter of English when it comes to supplying the answer in the right form.

    So how did I come to the conclusion ...? I guess I'd say it is a careful reading of the problem. As much as anything your course may encourage you to read with precision every bit as much as understanding equations.
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