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Need help with graphs of potential energy and force

  1. Nov 9, 2012 #1
    Hi everyone!!!

    1. The problem statement, all variables and given/known data

    The potential energy U of a point mass is U(x)= Uoxo x/(x2 + xo2) where Uo and xo are positive contants, Uo in joule and x,xo in meters. Draw the graphs of U(x) and F(x).


    2. Relevant equations

    F(x) = -dU/dx

    3. The attempt at a solution

    I found the F(x) function and made the U(x) graph but I'm stuck with the F(x) graph and I'm not totally sure for anything that I found so far.

    Thank you!!
     
  2. jcsd
  3. Nov 9, 2012 #2

    haruspex

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    Please post what you got for the F(x) function. For the graphs, either post your attempts or at least a verbal description.
     
  4. Nov 11, 2012 #3
    For the F(x) I found that it is V0x0 (x+x0)(x-x0) / (x2 + x02)2

    I can't make a graph out of it. As for the U(x) the graph is in the attachment below.
    U(x)=0 when x=0 and Vmax=V0/2 when x=x0
     

    Attached Files:

  5. Nov 11, 2012 #4

    haruspex

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    When sketching a graph, you should take it far enough to illustrate asymptotic behaviour. What is that for U(x)?
    I don't understand why cannot get a graph for F. What tool did you use to get the graph for U? You ought to be able to sketch graphs from the formula without using a plotting tool. That's how you know which sections are interesting to plot.
    Can you at least describe in words what F(x) would look like by inspection of the U(x) graph? Say what the asymptotic values are, over what ranges it would be positive, where the zeroes are, and all extrema.
     
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