1. Physics Mrs. Coyle -Gravitational Field -Satellites -Einstein’s View of Gravity

2. Gravitational Field: Space around a mass http://www.antonine-education.co.uk/New_items/STA/G-Field/field_2.gif

3. Gravitational Field Strength, g g= F m The direction of g is the same direction as F.

4. Problem 1: Express g in terms of F, G, m Earth, r.

5. Problem 2: Find the value of the gravitational acceleration g on the surface of the earth.. The mass of the earth is 6.0 x 10 24 kg and the radius of the earth is 6.37x10 6 m. (G=6.67x10 -11 N m 2 /kg 2 ).

6. Newton’s “Cannon” If a cannon were to be placed 150km above sea level, and shot a cannonball with a horizontal speed of 8km/s, the ball would fall to the earth 4.9m in one second. The earth’s surface curves down by the same distance, so the ball remains at the same height from the surface, thus orbits the earth.

7. Satellites

9. Problem 3: Find the tangential velocity of a satellite, that orbits the earth at a distance r from the center of the earth. Express the answer in terms of G, m e and r.

10. Solution:

11. Tangential Velocity of a Satellite at a given r do not depend on the mass of the satellite. __________ v=√(GM e /r) For a given r (distance from the earth) the speeds of the satellites are the same.

12. Geosynchronous Satellites: have the same period as the period of the earth. http://www.astro.virginia.edu/class/oconnell/astr121/guide08-s04.html

13. Einstein’s Theory on Gravity: General Relativity http://www.nature.com/nature/journal/v445/n7127/full/445468b.html

14. Einstein’s Theory on Gravity: General Relativity Matter causes space to curve. Objects and light near the mass follow the curvature of space. http://www.astro.physik.uni-goettingen.de/~hessman/ImageJ/Book/Microlensing%20-%20Hands-On%20General%20Relativity/

15. Einstein’s View on Gravity http://www.astronomynotes.com/relativity/s3.htm

16. Black Holes Extremely massive stars with extremely high gravity.