Solving 2 differential equations simultaneously
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I am trying to solve 2 equations with 2 variables.
Eq 1: w''(t)=-0.03.w'(t)/r(t)
Eq 2: w'(t)=-0.005.w(t)/r(t)
w(0)=0.6, w'(0) = 0.001, r(0)=12
I could not find a way to solve the 2 equations using ode45.
tspan=[0 500];
w0=0.6;
r0=12;
[t,w,r] = ode45(@angvel, tspan, w0,r0);
function dwdt = angvel(t,w,r)
dwdt = -0.005*w/(0.01*r);
end
The error when I try to solve Eq1 is insufficient inputs. Where am I going wrong? Please advise. Thanks!
2 个评论
Aquatris
2018-8-8
I might be wrong but the initial conditions do not seem to satisfy the equation 2. Are you sure these are the equations?
BHAGYASHREE WAGHULE
2018-8-8
编辑：BHAGYASHREE WAGHULE
2018-8-8
回答（1 个）
Diwakar Ravichandran
2018-8-8
0 个投票
Hi Bhagyashree,
As I was going through your equations, I noticed that when you substitute equation 2 in equation 1 we get,
w"(t) = (1.5*10^-4)*[w(t)/r^2(t)];
which is a single equation with 2 unknown variables and hence it cannot be solved using conventional methods. You would need to gather more information about the unknowns and their behavior to solve this equation.
Hope this helps,
Cheers!
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