Newtons theory of gravity : satelite orbits and ellipses

[marshall104]

The figure shows two planets of mass m orbiting a star of mass M. The planets are in the same orbit, with radius r, but are always at opposite ends of a diameter.
This is the equation eq. I used:

mv^2/r=GMm/r^2+Gmm/(2r)^2

This is what I came up with but it is not the right answer. Where did I go wrong?

sqrt4pi^2/G(M+m)*r3/2

Any help would be great!

 

[bp_psy]

The figure shows two planets of mass m orbiting a star of mass M. The planets are in the same orbit, with radius r, but are always at opposite ends of a diameter.
This is the equation eq. I used:

mv^2/r=GMm/r^2+Gmm/(2r)^2

This is what I came up with but it is not the right answer. Where did I go wrong?

sqrt4pi^2/G(M+m)*r3/2

Any help would be great!

What are you trying to find ?

 

[ZapperZ]

The figure shows two planets of mass m orbiting a star of mass M.

What figure?

Zz.

 

[marshall104]

I'm sorry. I'm trying to find T the orbital period