Re: Solving unknowns of kinematic equations in octave.

[Juan Pablo Carbajal]

On Wed, May 1, 2013 at 5:45 PM, ZachTM <address@hidden> wrote:
> Hello I am fairly new to octave but I have been playing around with fsolve.
> I want to make an octave program that can solve for the 5 possible unknowns
> in the kinematic equations. (vi,vf,a,d, and t)
>
> Would it be possible to somehow define these equations:
> <http://octave.1599824.n4.nabble.com/file/n4652529/KE1-3.jpg>
> And then when I define 3 or more of the variables it could solve for the
> other two?  I just dont know how I would get this to work with fsolve.  I
> could make an octave program that picks which equation it will use for every
> unknown but I would like to extend this to work with any set of equations
> and unknowns (within reason of course).  If the user doesn't give enough
> variables I would return an error.
>
> So can anyone tell me if this would be even possible?  And if fsolve would
> be appropriate to use here?  Any responses are greatly appreciated!
>
> Thanks,
> Zach
>
>
>
>
>
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Most of your equations (I do not know what's d!) are linear in the
variables you want, except for t and v_0 and v_f. So whenever you knw
those values you can solve a linear problem, i.e. matrix inversion.
When any of the "nonlinear" variables is unknown you could solve the
proper equation by hand and just return the solution. This accounts
for just a few cases. You can of course, use a nonlinear solver, but
it sounds to me that is a lazy (and probably slow) way of solving the
problem.