Suppose a planet with mass m is orbiting a star with mass M and the mean distance

Fantastic news! We've Found the answer you've been seeking!

Question:

Suppose a planet with mass m is orbiting a star with mass M and the mean distance between the planet and the star is a. Using Newton's law of universal gravity, derive an algebraic expression for the speed of the planet when it is at the mean distance from the star. (Use the following as necessary: G, m, M, and a.