Help in using bvp4c second order ODE.

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I am trying to solve this equation: 9,81-2,5*y^2+1,75* θ2y^2/θx2=0,15 (bc: y(0)=0,y(1)=0) The problem is that y is squared. I managed to find a solution for y^2 but not y. I tried to use the equation: θ2y^2/θx2=2*(y'*y'+y*y'') but I got an error:

Error using bvp4c Unable to solve the collocation equations -- a singular Jacobian encountered.

Any ideas on how to obtain a solution for y?

Thanks.

function bvp4 xlow=0; xhigh=1; solinit=bvpinit(linspace(xlow,xhigh,1000),[0 0]); sol = bvp4c(@bvp4ode,@bvp4bc,solinit); xint=linspace(xlow,xhigh); Sxint=deval(sol,xint); plot(xint,Sxint(1,:))

function dydx = bvp4ode(x,y) dydx = [y(2); (0.15-9.81+2.5*y(1))/1.75 ];

function res = bvp4bc(ya,yb) res = [ya(1); yb(1)];

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Answer 1

Torsten 2016-4-20

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If the above code works (for y^2), why not just taking the square root of the solution to get y ?

Best wishes

Torsten.

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SuzieQ 2016-4-20

Yes this could work, but where exactly in the bvp4c code should I declare that I want a solution for y? Thanks.

Torsten 2016-4-21

在 MATLAB Online 中打开

Nowhere.

Use

xint=linspace(xlow,xhigh); 
Sxint=deval(sol,xint); 
Sxint=sqrt(Sxint);
plot(xint,Sxint(1,:))

Best wishes

Torsten.

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Help in using bvp4c second order ODE.

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