# Homework Help: Distance from one focus to the other

1. Sep 15, 2007

Am I making this out to be too simple?

I am given: The Sun's center is at one focus of Earth's orbit, how far from this focus is the other focus in meters and in terms of the solar radius?

eccentricity=.0167
semimajor axis=a=1.5*10^11 meters.

Now if c is the distance from the focus to the center of the ellipse,

e=c/a implies c=ea.

So the foci should just be 2ea meters apart...for which I am getting 5.01^9 meters. Which seems reasonable (I think:uhh:)

Now I am having trouble with the latter part of the problem. I know it is just some sort of ratio. The text says 7.2 solar radii but does not give the answer in meters, so I cannot confirm that either.

Casey

2. Sep 15, 2007

AGAIN I AM A JERK!! I got it.

Casey

3. Sep 15, 2007

### HallsofIvy

Well, to find the ratio of the distance between foci to the "solar radius", you will need to know the solar radius! I take it that is the radius of the sun?

4. Sep 15, 2007