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Planetary and Satellite Motion

Planetary and Satellite Motion. (Math Excluded– Concept only). Satellite: any object that is orbiting a massive body. 2 Types: Natural Satellites include moons, comets, planets. Man-made Satellites are any man-made satellite. (common sense). A satellite is a projectile.

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Planetary and Satellite Motion

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  1. Planetary and Satellite Motion (Math Excluded– Concept only)

  2. Satellite: any object that is orbiting a massive body. 2 Types: • Natural Satellites include moons, comets, planets. • Man-made Satellites are any man-made satellite. (common sense).

  3. A satellite is a projectile. • The only force acting on it is gravity. • Speed must be great enough to prevent it from crashing to Earth.

  4. What’s the minimum speed? • The Earth’s surface curves about 5 m for every 8000 m. • It must travel 8000 m horizontally for every 5 m of vertical fall.

  5. It so happens that the vertical distance that a horizontally launched projectile would fall in its first second is approximately 5 meters (1/2gt2). • A satellite launched at 8000 m/s can orbit in a circular path (launched in an area w/o air drag).

  6. As the projectile travels tangentially a distance of 8000 m in 1 s, it will drop app. 5 m towards Earth. • It will remain the same height above the Earth due to the fact that the planet curves at the same rate.

  7. Weightlessness in Space • Astronauts in orbit often experience weightlessness. • Same sensation you get when you are suspended over your seat on a roller coaster.

  8. Remember contact vs. action at a distance forces

  9. You don’t feel an action at a distance force pulling on you in the same way as you do a contact force. • Ex: sliding across a tennis court (friction) being pushed by a jerk (applied) swinging from a rope (tension) • But, on a trampoline, you don’t really feel gravity pulling you in the same way. • But it’s there.

  10. Scales and Weight

  11. Astronauts in orbit are weightless for the same reason riders of a free-fall coaster or elevator are. • There are no external contact forces acting on them. • Without gravity, they would not be orbiting. They’d be flying into space towards their DEATH.

  12. Weightlessness does not mean gravity-less! • Repeat this 29x in your head.

  13. Misconception: the astronauts are weightless because the force of gravity is reduced in space. The reasoning goes as follows: "with less gravity, there would be less weight and thus they would feel less than their normal weight.“ • True, but it does not explain their sense of weightlessness.

  14. Yes, they experience less g, but the weightlessness comes from “having the floor pulled out from under them.” • Due to being projectiles.

  15. Others think there’s no gravitational force because there’s no air. • Gravity DOES exist in a vacuum.

  16. Geosynchronous satellites • Geosynchronous: always above the same area of sky. http://upload.wikimedia.org/wikipedia/commons/3/3a/Geostationaryjava3Dsideview.gif

  17. They have an orbital period the same as the Earth's rotation period. • Period:amnt of time to complete one orbit • An idea popularized by Arthur C. Clarke (wrote 2001: A Space Odyssey and other sci-fi books).

  18. Over 600 GS satellites in orbit. • High altitude…means slight signal delay. • Uses: global communication, satellite tv, weather forecasting, defense apps, GPS.

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