Inhomogeneous second order ODE with non-constant coefficient

In summary, the student is trying to solve a problem involving a spherical polar and trying to find the radial component. They found that there are two solutions, depending on the sign of the rescaled constant.
  • #1
jmz34
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0

Homework Statement



Solve ODE of form y''+(2/x)y'=C*(e^y) where C is a constant

Homework Equations





The Attempt at a Solution



I don't really see how to approach this one, so a point in the right direction would be great.

Thanks,
 
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  • #2
Where did you get this problem from ? I'm almost sure there's no analytical solution (Mathematica couldn't find any combination of elementary/special functions which would satisfy the equation) to it, so an approximate solution would be the best you could ask for.
 
  • #3
bigubau said:
Where did you get this problem from ? I'm almost sure there's no analytical solution (Mathematica couldn't find any combination of elementary/special functions which would satisfy the equation) to it, so an approximate solution would be the best you could ask for.

I was trying to solve del^2(Psi)=Ae^(Psi) in spherical polars, for the radial component.

Checking over my algebra I'm pretty sure it's correct.
 
  • #4
Yes, it looks correct. However, my guess is that the nonlinearity in the RHS spoils the <neat> intregrability.
 
  • #5
bigubau said:
Yes, it looks correct. However, my guess is that the nonlinearity in the RHS spoils the <neat> intregrability.

Thanks a lot for your help. The question does say that Psi varies over a length scale that is approximately the same as the region which I'm supposed to be analyzing. Does that somehow mean I can take the RHS as constant?
 
  • #6
Not really, rather approximating it to y(x). That way you get an ODE which can be integrated in terms of elementary functions.

And the C needs to be specified, the sign of it is important. You may rescale it to +1 or -1, I'm sure.

As for how to solve the following 2 ode's

[tex] y''+ \frac{2}{x}y'\pm y = 0 [/tex]

use the substitution

[tex] y(x) = \frac{u(x)}{x} [/tex]

You'll find 2 classes of solutions, depending on the sign of the rescaled constant.
 
  • #7
Ofcourse. Thanks again.
 

What is an inhomogeneous second order ODE with non-constant coefficient?

An inhomogeneous second order ODE with non-constant coefficient is a type of differential equation that involves a second derivative, a non-constant coefficient, and a non-zero function on the right-hand side of the equation. It is a more complex type of ODE compared to a homogeneous second order ODE with constant coefficient.

What makes an inhomogeneous second order ODE difficult to solve?

The non-constant coefficient in an inhomogeneous second order ODE can make it difficult to solve because it cannot be factored out like a constant coefficient. This means that the usual methods for solving ODEs, such as separation of variables or using an integrating factor, may not work. Instead, more advanced techniques such as variation of parameters or the method of undetermined coefficients may be needed.

What are some real-life applications of inhomogeneous second order ODEs with non-constant coefficient?

Inhomogeneous second order ODEs with non-constant coefficient can be used to model a variety of physical phenomena, such as the motion of a damped harmonic oscillator, the behavior of an electric circuit, or the growth of a population with a varying rate of change. They are also commonly used in engineering and physics to describe systems that involve non-linearities and external forces.

How can I check if my solution to an inhomogeneous second order ODE with non-constant coefficient is correct?

To check if your solution is correct, you can substitute it back into the original ODE and see if it satisfies the equation. You can also take the first and second derivatives of your solution and see if they match the original ODE. Additionally, you can compare your solution to known solutions or use numerical methods to approximate the solution and compare it to your own.

What are some tips for solving inhomogeneous second order ODEs with non-constant coefficient?

Some tips for solving inhomogeneous second order ODEs with non-constant coefficient include trying to simplify the equation by making a substitution or using a symmetry argument, looking for patterns in the non-homogeneous term, and being familiar with a variety of solution techniques such as variation of parameters and the method of undetermined coefficients. It is also helpful to practice solving different types of inhomogeneous second order ODEs to build your problem-solving skills.

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