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Asked by Kyle on 12 Apr 2013

I am trying to create a code to: 1) Solve this differential Equation for h(t) (or h2) in terms of t. 2) Solve for t at a certain h2. 3) Plot h2 versus t

the equation is (dh/dt)=(-36290.323)*[(((2*mw*g*t)/(Gama*Atank))+(2*g*h))^(1/2)]

Thank you for your help.

Answer by Youssef KHMOU on 12 Apr 2013

hi Kyle,

You can try as the following :

1) Create a function in M-file inwhich you define the equation :

function dh=MYFunc(t,h) %(dh/dt)=(-36290.323)*[(((2*mw*g*t)/(Gama*Atank))+(2*g*h))^(1/2)] A=-36290.323; mw=2.33; g=9.81; Gamma=1.23; Atank=4; dh(1)=A*(((2*mw*g*t)/(Gamma*Atank))+(2*g*h(1))).^(1/2);

2) In the workspace you call the function "ode23" or "ode45" as :

t0=0; % staring time tf=10; % t final Initial_value=2; % the initial value for h [t,h]=ode45('MYFunc',t0,tf,[Initial_value]); figure, plot(t,abs(h));

Adjust the parameters, and try ...because in this case h is complex .

Kyle on 12 Apr 2013

Thank you for your help Youssef.

Code is working great. One question I have about the code for part 2. I have the final value of h that I am looking for. Is there a way to plug in the initial and final values to get tf?

Youssef KHMOU on 12 Apr 2013

hi Kyle,

no i can not tell, that may be possible if we already know the Sampling frequency of t .

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