In Jules Verne's original problem, find the minimal launch velocity that suffices for the projectile to make it "From the Earth to the Moon". (To reach the moon, the projectile must only just pass the point between the moon and earth where its net acceleration vanishes.)
S is the distance between the centers of the earth and the moon and is = 384,000 km
R is the radius of the earth and is = 6,378 km
Let r be the distance of the projectile from the center of the earth.