Intro to Gravity - St. Mary's Physics

 

I. Satellite Motion

 

Satellite - smaller body revolving around a larger body

 

Natural Satellites ex) Moon, all 8 planets, comet

 

Artificial Satellites - weather, spy, communications

See where the earth's satellites are right now!

JTrack3D

                Click this link and wait until the program jumps to the screen.

 

A. Satellite Motion

 

1. To send artificial satellite in circular orbit around earth it must first achieve a speed of 7900 m/s

 

If greater than 7900 m/s satellite has an elliptical orbit

 

If velocity is greater than 11 km/s then satellite leaves earth's orbit (called escape velocity)


2. Air resistance slows down satellites and eventually causes them to spiral back to earth.

Peekskill Fireball - Meteorite Peekskill, Ct. (NASA)

Barringer Meteorite Crater

David Roddy, USGS.

B. Geosynchronous Orbits -

a. When a satellite orbits in time with earth’s rotation it is called geosynchronous.
 
b. Time for one revolution - 24 hrs
 
c.  A satellite at distance of 6 earth radii from earth's center will orbit earth every 24 hrs.
 
d. Since both satellite and earth move together, it always remains directly above same spot above earth’s equator.