Physics
posted by Joe .
On July 19, 1969, Apollo II's orbit around the moon was adjusted to an average height of 188 kilometers above the moon's surface. The radius of the moon is 1810 kilometers, and the mass of the moon is 7.3 x 1022 kilograms.
a. At what speed did it orbit the moon?
b. How many minutes did it take to orbit once?

m gmoon = m v^2/r
where r is the orbit radius
r = 1.81^10^6 +.188*10^6 meters
g moon = G Mmoon/r^2
so
v^2 = gmoon * r
square root of that is v
then
2 pi r = distance around orbit
v = speed
time = distance / speed