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ptc-51207371-Visitor
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May 14, 2014
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MC 15 Equation Solving

  • May 14, 2014
  • 3 replies
  • 1776 views

I'm trying to familiarize myself with using Mathcad to solve complex equations. My understanding is I should state a guess for the variable, state the given and then use the find command, but this isn't working. Can anyone point out my error in the attached file?

    Best answer by AlanStevens

    Do you really want to match a velocity around 10^16 times the speed of light?!!! The best the relativistic equation you use can do is to get up to the speed of light. Because this is way short of your target, Find won't do it. You could use Minerr - see below - but you know in advance that you can't get beyond v = c!!

    warp.PNG

    Alan

    3 replies

    A
    AlanStevens19-TanzaniteAnswer
    19-Tanzanite
    May 14, 2014

    Do you really want to match a velocity around 10^16 times the speed of light?!!! The best the relativistic equation you use can do is to get up to the speed of light. Because this is way short of your target, Find won't do it. You could use Minerr - see below - but you know in advance that you can't get beyond v = c!!

    warp.PNG

    Alan

    Werner_E
    Werner_E25-Diamond I
    25-Diamond I
    May 14, 2014

    Can anyone point out my error in the attached file?

    You didn't make any error. It is a good habit to add units to the guess value, but it is not necessary in Mathcad in case of the value being zero (this might be different in Prime with its dynamic unit checking).

    Your equation is not defined for v=c but the solution of v is around this value and so the numeric solve block fails. The error message you get is wrong but its the only message you will ever get from a solve block.

    Change the 10^25 to something significant smaller like 10^5 and you get a solution.

    In case of simple equations you may try to use the symbolic solver:

    st1.png

    st2.png

    F
    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    May 14, 2014

    If you plot the function v/sqrt() you will see that it becomes imaginary when v is larger than c.

    You can have a solution; just not for the value you wanted on the RHS

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