Hi,

sorry for that question, i'm a beginner in maple but i think my question is not as simple.

So, i want to solve numerically this first equation :

but the second term is present only if k*(U*t-x)>μc*m*g  (stick-slip problem)

initial conditions : U=1m/s; x=0m; k=10 for example

My problem is simple, i don't know how to use conditional statement for such an ode in maple.

I've tried > Xr := U*t-x;
> k := 10; m := 1; g := 10; mu := .2;
> if k*Xr > mu*m*g then ode1 := m*(diff(x(t), t, t)) = k.Xr-mu*m*g else ode1 := m*(diff(x(t), t, t)) = k.Xr end if;

But, of course, too optimistic.

Thank to anyone who will solve that (isuppose) simple problem

Philippe

Hi,

i make an attempt to plot the solution to

Here is my code :

> with(plots); with(DEtools);
> ode1 := diff(x(t), t) = v(t); ode2 := diff(v(t), t) = -(.8*9.8)*v(t)/abs(v(t))-cos(t)^2;
> MODEL := {ode1, ode2}; VARS := {v(t), x(t)}; DOMAIN := t = 0 .. 150; RANGE := x = -1 .. 1, v = -5 .. 5; COLORS := [BLACK, BLUE]; IC1 := [x(0) = .5, v(0) = .25]; IC2 := [x(0) = 2.5, v(0) = 3];
> DEplot(MODEL, VARS, DOMAIN, RANGE, [IC1, IC2], stepsize = .1, linecolor = COLORS, scene = [t, x]);
>

and the message cannot evaluate the solution further right of .16015784, maxfun limit exceeded (see ?dsolve,maxfun for details)

Any other attemp has failed.

Have you got somme ideas

Thanks

Phil

Hi,

I would like a plot of the solution of this differential equation : diff(phi(x),x,x)=phi(x)*(Ep(x)-E) with for example Ep(x)=(1-exp-(x-2))^2 and E=0.5

So :

>restart;with(plots); xith(DEtools);

>Ep:=x->(1-exp-(x-2))^2;E:=0.5;

>sol:=dsolve({eq,phi(o)=0,D(phi)(0)=0},type=numeric,range=0..10);

>odeplot(sol);

but nothing appear in the plot except axes

Thanks for answer

Hi,

I obtain  curve pH = f(Vb) with following code

restart;with(plots);

 Vtot := V0+Vb+Vind;h := 10^(-ph);C0 := 10^(-2);Cind := .83;Vind := 0.1e-1;V0 := 10;Ka1 := 10^(-4.8);Ka2 := 10^(-9);Cb := 0.1e-1;Kaind := 10^(-8);

eq := h+Cb*Vb/Vtot = 10^(-14)/h+C0*V0/(Vtot*(1+h/Ka1))+Cind*Vind/(Vtot*(1+h/Kaind));

 implicitplot(eq, Vb = 0 .. 40, gridrefine = 3, ph...

Hi,

I obtain  curve pH = f(Vb) with following code but now, i would have tangent for two points near Veq. I don't know the procedure with implicitplot.

I think the best way is to attribute the points to a function but dn't know how to do

restart;with(plots);

 Vtot := V0+Vb+Vind;h := 10^(-ph);C0 := 10^(-2);Cind := .83;Vind := 0.1e-1;V0 := 10;Ka1 := 10^(-4.8);Ka2 := 10^(-9);Cb := 0.1e-1;Kaind := 10^(-8);

eq := h+Cb*Vb/Vtot = 10^(-14...