Calculating Velocity for an Orbit Near Earth's Surface

[kellypmk1]

Homework Statement

"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?"

Homework Equations

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

The Attempt at a Solution

 

[Dick]

I think it's mainly sort of an 'concept' question. If the ball was in orbit, and the ground level dropped 32 feet after going 30000 ft, how far should the ball drop after traveling that same distance?

 

[kellypmk1]

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.

 

[Dick]

That's exactly the sort of answer we are after. But you didn't answer my question. But I'll continue anyway. Next question is how long does it take for a ball with zero initial vertical velocity to drop 32 ft?