How fast would an object have to move to stay in Earth orbit at treetop level?

Question

Things stay in orbit by moving fast enough to resist gravity, right? And the more mass an object has, the slower it can move without falling out of orbit. So how fast would an object the size of an airliner have to be moving to stay in orbit at treetop level, "flying" without wings? I know it's impractical, but just curious.

Answer 1

Mass has nothing to do with it:

v^2/r = g; v = sqrt(rg) = sqrt(6.4 x 10^6 m x 9.8 m/s^2) = 7200 m/s = 28500 km/h

At this speed, the object would circle  the earth in just under an hour and a half.

Answer 2

wasn't that a short story by Isaac Asimov?

only it was on Mars?

<edit>

looks like i need to correct myself.  Some guy named McGruff posted this:

""My favorite form within the sci-fi genre is the short story, and one especially cute little tale that stuck in my head is about Mars. I read "The Holes Around Mars" by (Jerome) Bixby in an anthology, although it was most likely first published in a magazine. As with some of the best sci-fi stories, this one includes a good bit of humor. The story is about solving the mystery of a series of holes that the first human explorers discovered when they landed on the planet. Eventually, they find that these are caused by a moon orbiting so low that people have to duck so as not to be in its path. The final pun is a real groaner. Because the other two moons of Mars are called Phobos and Deimos, this lowest orbiting moon is named Bottomos.""

Answer 3

  This tree top level thing.. Don't think you could get anything going fast enough. Think the shuttle orbits at 12,000 mph with no resistance.

  It's what is inside the Earth's atmosphere that makes this one impossible

Answer 4

Faesson stole my thoughts. I remember that short story, and thought of it as soon as I read your question.

.

Answer 5

  It would have to travel at about 25,000 miles per hour no matter how big or massive it was.