3. Spring 20082 4 km/s: Not Fast Enough....

4. Spring 20083 6 km/s: Almost Fast Enough....but not quite!

5. Spring 20084 8 km/s: Not Too Fast, Nor Too Slow....Just Right

6. Spring 20085 10 km/s: Faster Than Needed to Achieve Orbit

9. Cannonball A cannonball is fired horizontally from a tall mountain to the ground below. Because of gravity, it strikes the ground with increased speed. A second cannonball is fired fast enough to go into circular orbit but gravity does not increase its speed. Why Refer to #19 & #23 in conceptual physics

10. At the orbital speed, the force of gravity is perpendicular to the motion

12. MOON MOTION Draw a Force Diagram and sum the forces acting on the moon as it orbits the earth. If the moon orbits the earth every 27.3 days at a radius of 3.8 x 10 8 meters. Determine the velocity and the acceleration due to gravity that the moon experiences.

14. F g = G = MemMem _________ r² ____ r mv 2 Speed of a Satellite:

15. v = √ GM e r Speed of a Satellite:

16. v = velocity (m/s) G = gravitational constant M e = mass of Earth (kg) r = distance to center of the Earth (m)

18. Satellites What is the minimum velocity needed for a satellite to stay in orbit at 1500 km above the earth’s surface. Given M earth = 5.98 x 10 24 kg R earth = 6.37 x 10 6 m And the answer is…. 7913.047866 m/s

19. TREETOP ORBIT If the earth had no air (atmosphere) or mountains to interfere, could a satellite given adequate initial velocity orbit arbitrarily close to the earth’s surface – provided it did not touch? a)Yes, it could. b)No, orbits are only possible at a sufficient distance above the earth’s surface where gravitation is reduced. Explain.