# Accelaration of gravity g(t)=?

rcgldr
Homework Helper
The solution to problem should be ready as the one of the "Two body problem". At least it seems so as I see at the wikipedia article on it. Why didn't you get the equations of that at the first place?
I don't recall, the newer thread was a continuation of the older thread, and there were prior threads. Someone just wanted to see the math worked out starting with basic gravity equations for acceleration versus distance between objects.

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gabbagabbahey
Homework Helper
Gold Member
Well, the math worked out are supposed to be explained at the article http://en.wikipedia.org/wiki/Kepler_orbit.

But already the equation m1r''1=... does not say how it is derived.
If you are referring to the equation $$m_1\ddot{\vec{r}}_1=\frac{Gm_1m_2}{r^2}\hat{r}$$ , that's just Newton's second law (and the universal law of gravitation of course) applied to mass $m_1$ ($\vec{r}_$ is the mass' position vector at any given time, so its second time derivative is the mass' acceleration at any given point in time).

(deleted by poster)

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It is the Two Body Problem:

What is the r(t)=(distance of m from M at t), given the initial (x,y) coordinates-vector for the position of M and m and the velocity of m, where M is at the centre of the axises xy, and the axises move with M so that it is stationary in that reference frame?

I am not even sure if the question is correct, but I fear that I will instist for months on finding its answer.

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