# Gravitation course work

1. Apr 18, 2008

### Tom1

1. The problem statement, all variables and given/known data

A planet around a star has an orbit that is not exactly an ellipse. In addition to the dominant Fo $$\alpha$$ r^-2 term due to gravity from the central star, the planet seems to be responding to a slight additional force which has the form F1 $$\alpha$$ r^-$$\alpha$$ where $$\alpha$$ is some constant.

2. Relevant equations

Included in 1.

3. The attempt at a solution

Where do I begin?

2. Apr 18, 2008

### Kurdt

Staff Emeritus
I have no idea since I don't know what you're supposed to be doing.

3. Apr 18, 2008

### Tom1

Sorry, part of this seems to have been cut off.

Assuming there is a slight background density of material with spherically symmetric density p1 falling off as p1 (alpha) r^-B

Find the value of B in terms of alpha

4. Apr 18, 2008

### Tom1

Can anyone help me get started please? I don't understand this at all and it's due soon.

5. Apr 18, 2008

### Dick

Near as I can tell you want to assume there is a mass distribution with density rho(r)=p1*(r/r0)^(-B). Now you want to figure out the radial dependence of the force it generates. Compute total mass as a function of r, M(r). Use that to calculate the force.