I'd just like to bump in here saying the orbital velocity of any spacecraft is dependent on the size and mass of the orbiting body as well as the apogee and perigee of the orbit. This means not all spacecraft go at 17,400 miles per hour around the earth. A GPS satellite in an orbit of around 20,000 km will go much slower than the Soyuz which operates at 200 to 300 km.
This also applies to celestial bodies. Uranus (stop giggling) has not yet completed an orbit around the sun since its discovery, while mercury orbits the sun every 88 days or so.
I highly suggest both RE'ers as FE'ers read on Kepler's Laws of Planetary Motion, Newton's laws of motion and universal gravitation, and if you have some free time play a game called Kerbal Space Program. It's more exciting and easier to pick up than orbiter, and is great for understanding all the maths involved in these "elaborate satanist baby murdering money-laundering hoaxes".
Heck, if you REALLY have free time, test these laws for yourself and grumpily admit that the math is sound or grumpily dismiss these old dead guys and their stupid math. Maybe math just makes everyone grumpy?