ch14_jdzr

Zach Rosinger Jon Difiore Pd. #8

=**Chapter 14 Satellite Motion**=

An earth satellite is a projectile that "falls" around the earth, not "into" it. In order for an object to go into motion as a satellite, it needs to be moving fast enough to never fall into earth. Earth drops 5 meters for every 8000 meters tangent to its surface. The orbital speed for earth is around 8 km/s, and the object must remain about 150 kilometers or more above the earth's surface in order to not be burnt by atmospheric friction.
 * 14.1 Earth Satellites:**



An object in circular orbit will always travel at the same speed and distance from the earth, because while in orbit, an object is not affected by gravity. A satellite is not affected by gravitational forces because gravity is only a downward and upward force. A satellite moves in a perpendicuar path throughout a circular orbit, so that is why a satellite is not affected by gravity.
 * 14.2 Circular Orbits:**
 * **Period** - The time it takes for one complete orbit around the earth. If the a satellite is close to the earth, the period is about 90 minutes. For higher altitudes the period is longer because the orbital speed is less.

A projectile above the earth's atmosphere at a horizontal speed a little more than 8 km/s will overshoot the standard circular path and thus create an **ellipse.** The sum of the two fixed points (foci) will create the ellipse. Satellite speed in a circular orbit is constant, whereas the speed inside an elliptical orbit varies depending on the location of the satellite in the ellipse.
 * 14.3 Elliptical Orbits:**



Potential Energy (PE) is greatest with a satellite when it is furthest away (a.k.a. **apogee**). Kinetic Energy (KE) will be the greatest for a satellite when it is closest (**perigee**). At all of the points aside from the apogee and the perigee, there is an amount of gravitational force parallel to the direction of the satellite.
 * 14.4 Energy conservation and Satellite Motion:**

To achieve orbit, a satellite must be launched //horizontally// at 8 km/s, not vertically. If it is launched vertically at 8 km/s, then it would not go into orbit, it would, instead, come crashing back down at the same speed, 8 km/s. The **escape speed** of an object that is going to leave the atmosphere is the speed in which the object needs to travel in order to break gravitational pull and go into either orbit, or completely leave earth all together. This speed is usually 11.2 km/s, or 62 MJ/kg. (MJ = million joules).
 * 14.5 Escape Speed:**