2nd order DE for planet's density

In summary, The conversation is about finding the density as a function of radius in a problem related to the Lane-Emden equation. The equation and initial conditions are not explicitly given and must be solved in an iterative manner using mathematica. The goal is to determine the maximum and minimum values of theta (density) at r = 0 and r = R respectively.
  • #1
dinospamoni
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Homework Statement



I attached the problem because it's easier

Homework Equations





The Attempt at a Solution



The main problem I have with this problem is trying to find the density as a function of radius.
I have been thinking for hours but can't come up with anything.

What I have for the n=0 question:
for clarity, I'm just using x

θ''+(2/x)θ' +1 = 0

is my equation and I'm using mathematica to numerically solve it.
 

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  • #2
The variable theta is defined as the density of the body as a function of radius. Theta is not given explicitly in terms of r, but the values of theta are determined by solving the Lane-Emden ODE subject to the initial conditions specified in the text. As the text describes, the initial conditions themselves are not explicit, and the Lane-Emden equation must be solved in an iterative fashion while manipulating the initial conditions. Basically, follow the recipe given in the text and check the values of theta to see if they give a maximum value when r = 0 and a minimum value when r = R (the surface of the body).
 

1. What is a 2nd order differential equation for a planet's density?

A 2nd order differential equation for a planet's density is a mathematical equation that describes how a planet's density changes with respect to its radius and mass. It takes into account the gravitational force acting on the planet and relates it to the planet's density at different points.

2. Why is a 2nd order differential equation used for studying a planet's density?

A 2nd order differential equation is used because it accurately represents the relationship between a planet's density, radius, and mass. It takes into account the complex factors that affect a planet's density, such as gravity, and provides a more accurate understanding of how a planet's density changes at different points.

3. How is a 2nd order differential equation solved for a planet's density?

A 2nd order differential equation for a planet's density can be solved using mathematical techniques such as separation of variables, substitution, and integration. These techniques allow us to manipulate the equation and solve for the unknown density values at different points on the planet.

4. What factors influence the shape of a 2nd order differential equation for a planet's density?

The shape of a 2nd order differential equation for a planet's density is influenced by several factors, including the planet's mass, radius, and gravitational force. Other factors that may influence the shape of the equation include the planet's composition, rotation, and external forces such as tidal forces from nearby objects.

5. How does a 2nd order differential equation for a planet's density relate to the planet's overall structure?

A 2nd order differential equation for a planet's density is closely related to the planet's overall structure. By solving the equation at different points, we can determine the density distribution and how it changes with depth. This, in turn, provides insight into the planet's internal structure and composition.

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