1. Satellite Motion

2. Curvature of Earth
The Earth’s surface drops 5 vertical meters for every 8000 meters tangent to its surface
8000 meters
5 meters
8000 meters
5 meters

3. How fast does an object need to go to become an Earth satellite?
How far does an object fall in 1 second? 5m
How far along the horizon must you go for the Earth to curve 5m down?
8000m
8km/s for orbital speed close to Earth!

4. The period for a satellite in low-Earth orbit is about 90 minutes.
Circular Orbit
Does the force of gravity affect the speed of a bowling ball down an alley?
Nope!
Similarly, the force of gravity of the Earth does not affect the speed of a satellite in circular orbit.
Why?
90 degrees between force and direction of motion…No Work!
The period for a satellite in low-Earth orbit is about 90 minutes.

5. At which position does the satellite have its greatest speed? Why?
Same speed Everywhere along path! C B D
A close Earth satellite has a period of about 90 minutes. A

6. Kepler’s 1st Law of Planetary Motion
What if an object above the atmosphere has a horizontal speed of more than 8km/s?
Its path is that of an ellipse instead a circle.
Most satellites actually have elliptical paths!
Speed varies in elliptical orbit
Johannes Kepler

7. Ellipse
Foci- Where the main body of an orbiting pair lies

8. At which position does the satellite have its greatest speed? Why?
Lowest Speed C D B
Greatest Speed A

9. Kepler’s 2nd Law of Planetary Motion
Apogee- when satellite is at farthest position
Slower when far away
Equal areas swept out over same amounts of time time!
Perigee- when object is at closest position
Faster closer to other source of gravity

10. Energy Conservation and Satellite Motion
The sum of potential and kinetic energies of a satellite remains constant

11. KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE

12. “What goes up must come down” or does it???

13. Escape Velocity
The speed necessary to put a payload infinitely far from Earth.
11.2 km/s horizontally or about 25,000 mph

15. Bonus
List all the planets in our solar system from lowest escape velocity to highest and explain how you did it.