1. Satellites What keeps them in orbit?

2. Satellites A satellite is any projectile given a large enough velocity so its path follows the curvature of the earth.

3. How fast is the earth moving? The earth moves 8000 m in the “X” direction and 4.9 m in the “Y” direction every second. Therefore, if a projectile moves equal or greater than that speed it will follow the curvature of the earth (it will never collide with earth)

4. Satellite in Orbit (cannonball example)

5. What makes a satellite go? All objects in circular motion must have an applied force (usually thrust force). The centripetal force (inward force) acting on a satellite is gravity. Gravity pulls any satellite towards the center of the earth. Gravity must equal applied force in order for satellites to orbit What happens if its less? greater?

6. Facts about satellites As the distance from earth increase:  Radius increase  Force of gravity decreases  Acceleration decreases  Result = required velocity is less

7. Satellite problem constants Radius of the earth = 6.38 x 10 6 m Mass of the earth = 5.97 x 10 24 kg Remember…the radius of a satellite is the height above the surface of the earth plus the radius of the earth.

8. Satellites d = distance above Earth + radius of Earth Use meters!

9. Satellite Practice Problems #1 Find the altitude of a satellite orbiting earth if it is moving at 6,900 m/s and the pull of gravity is 5.69 m/s 2 Answer: a = v 2 r Solve for “r”

10. Satellite Practice Problems #1 R = (6,900 m/s) 2 5.69 m/s 2 R = 8.4 x 10 6 m - 6.38 x 10 6 m R = 2.02 x 10 6 m

11. Satellite Practice Problems #2 Find the velocity needed to keep a satellite orbiting if it is accelerating at a rate of 8.2 m/s 2 and it is 5.00 E5 m above the surface of the earth. Answer: a = v 2 r v 2 = a x r …v = (sqrt)8.2 x 6.87 E6 m v = 7500 m/s