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Adam
06/26/10 11:51am

Hi,
I work on mathematica 7 and I do not know how to plot z1'[t] function.

I solve 2 equations and plot solution.
sk = NDSolve({L1 /(g*A1)*Q1'[t] == H0 - z1[t] - k*Q1[t]*Abs[Q1[t]],
z1'[t] == (Q1[t] - Q2)/As,
Q1[0] == Q0,
z1[0] == H0
}, {Q1[t], z1[t]}, {t, 0, 10000}];
(*Plot Charts*)
Plot[z1[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], z1[m]} ]
Plot[Q1[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], Q1[m^3/s]}]

That work fine, and when I try
Plot[z1'[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], z1[m]} ]
The output is just a coordinate system.

How to get value of a function?

in) z1[10]/.sk
out) {z1[10]}

Thank You for help.

Attachment: Untitled-1.nb, URL: ,

Subject (listing for 'first derivative from numerical solution')
Author Date Posted
first derivative from numerical solution Adam 06/26/10 11:51am
Re: first derivative from numerical solution yehuda ben-s... 06/27/10 08:41am
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