Orbit and speed

1. The problem statement, all variables and given/known data

"If the curvature of the earth were such that the surface dropped 32 feet for every 30,000 feet, how fast would a ball have to be thrown to put it into a orbit near the ground?"


2. Relevant equations

I have no idea where to begin. Do I use a formula for velocity?

3. The attempt at a solution

 

Thanks for the quick response. I was leaning toward that as well but then the instructor released the answer (21,289 ft/sec) but didn't explain how he arrived at that so now I am confused.