# Tb / Ta = ?

1. Mar 9, 2005

### the_d

Tb / Ta = ??????

i have a final question, which is how do i find this. i know what the question is askin i just dont understand how to get the answer

Two planets A and B, where B has twice the
mass of A, orbit the Sun in elliptical orbits.
The semi-major axis of the elliptical orbit of
planet B is two times larger than the semi-
major axis of the elliptical orbit of planet A.
What is the ratio of the orbital period of
planet B to that of planet A?

2. Mar 9, 2005

### dextercioby

HINT:Apply the 3-rd law of Kepler...

Daniel.

3. Mar 9, 2005

### James R

What is the equation which relates the semi-major axis of an orbit to the orbital period?