Physics
posted by Casey .
A binary star system consists of two equal mass stars that revolve in circular orbits about their center of mass. The period of the motion, T=29.6 days, and the orbital speed v= 220 km/s of the stars can be measured from telescopic observations. What is the mass (kg) of each star?

Each has a force holding it to the other.
F=GM^2/d^2
this is equal to centripetal acceleration.
GM^2/d^2=v^2/(d/2)^2
check my thinking. solve for M 
Using Newton's law and the law of universal graviation:
F=ma
Acceleration is centripital acceleration, so a=(v^2)/r
so G(m^2/r^2)=m(v^2/r)