Math
posted by Chris on .
The radius of Earth is 3,959 miles. A spacecraft orbits 6 miles above the surface of Earth. The spacecraft completes 220° of a revolution around Earth in one day. What is the average speed of the spacecraft?

This is a neat trick, as Earth is not spherical, the difference in radius at the poles compared to the Equator is 31miles.
Ignoring that bit of fact, assuming the Earth is spherical, and there is no atmospheric drag,then
period=1day=24hrs*3600sec/hr
speed=distancearund/tperiod=2PI(3959+6)/periodabove. 
oops, I missed the 220 degrees, so period=2PI(3965)*360/22O

Hi Bob  I have 4 possible answers and cannot arrive at any of them by the above. My choices are (a)634mph (b)1038mph (c)761mph (d)113mph