more help please physics?

Question

A typical GPS (Global Positioning System) satellite orbits at an altitude of 4.1 107 m.
(a) Find the orbital period of such a satellite.
hours
(b) Find the orbital speed of such a satellite.
km/s

Answer 1

Equate the gravitational force to the centripetal force

Fg = mv^2/r

(GMm)/r^2 = mv^2/r, solve for v

v = sqrt(GM/r)

The period is (2Pi)r/v = (2Pi)rsqrt(r/GM)

where r = radius of earth + distance to orbit
G = gravitational constant
M = mass of Earth

Answer 2

As I said.