differential equations solution doesnt work

i have for example
syms x y(x)
M4=(R1*x-p*g*pi*0.0810*(x-l1/2)-0.2626*p*g*pi*(x-K1-l2/2)-0.0630*p*g*pi*(x-K2-l3/2)-p*g*pi*((5*x - 19)*(3025*x^2 - 49225*x + 219217))/4704000)/E4/(pi*(b*x+c)^4/64);
%with all the variables known
and i type
ode = diff(y,x,2) == M4;
conds = [y(K4)== 1.7536e-04 Dy(K4)== -2.6143e-04];
ySol(x) = dsolve(ode,conds);
ySol = vpa(simplify(ySol))*10^(6)
yesterday i could solve the equation but today i try it and it continuous running without stopping
Also when i int M4 the result is different from the result yesterday this one does not have and log in it or fantastic number
how can i fix this?

6 Kommentare

darova
darova am 21 Nov. 2019
Did you try to solve it numerically?
Walter Roberson
Walter Roberson am 21 Nov. 2019
Please post values for all of the constants.
To verify: Dy is diff(y) ?
Dimitrios Adam
Dimitrios Adam am 22 Nov. 2019
Bearbeitet: Walter Roberson am 22 Nov. 2019
for some reason when i write
I=vpa((R1*x-p*g*pi*0.0810*(x-l1/2)-0.2626*p*g*pi*(x-K1-l2/2)-0.0630*p*g*pi*(x-K2-l3/2)-p*g*pi*((5*x - 19)*(3025*x^2 - 49225*x + 219217));
and i put I in M4 is working but when i leave it like the original it doesnt work . why?
Also the values are numbers
Walter Roberson
Walter Roberson am 22 Nov. 2019
Please post values for all of the constants.
When you do that assignment to I, are you using I/E4/(pi*(b*x+c)^4/64) in place of the M4 you defined before?
Dimitrios Adam
Dimitrios Adam am 23 Nov. 2019
Bearbeitet: Walter Roberson am 23 Nov. 2019
R1=78055; l1 = 1.6; g=9.81; p=7860; K1=l1; K2=3 ; l2=1.4 ; l3=0.8 ;b=-0.5/2.8; c= b*l1-1;
Yes i put it in the place of M4 defined before
The expression
I=vpa((R1*x-p*g*pi*0.0810*(x-l1/2)-0.2626*p*g*pi*(x-K1-l2/2)-0.0630*p*g*pi*(x-K2-l3/2)-p*g*pi*((5*x - 19)*(3025*x^2 - 49225*x + 219217));
is missing two ) somewhere. As we are not familiar with the underlying equations, we will have to get you to make the repair.

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