posted by mymi .
A planet with a mass of (7*10^21) kg is in a circular orbit around a star with a mass of (2*10^30) kg. The planet has an orbital radius of (3*10^10) m.
(a) What is the linear orbital velocity of the planet?
(b) What is the period of the planet's orbit?
(c) What is the total mechanical energy of the planet?