1. Planetary Motion 4/28/14 19-1b pgs. 515-518 IN: What causes night and day?

2. Planetary Motion Most objects in space move according to strict physical laws. Most objects in space move according to strict physical laws. The way in which the Earth moves, for example, causes seasons and even day and night. The way in which the Earth moves, for example, causes seasons and even day and night.

3. Rotation – the spinning motion of a body on its axis. Rotation – the spinning motion of a body on its axis. On Earth rotation causes night and day.On Earth rotation causes night and day.

4. Rotation As the Earth rotates, only one-half of the Earth faces the sun at any given time. As the Earth rotates, only one-half of the Earth faces the sun at any given time.

5. Day Night Cycle

6. Night and Day http://www.cs.sbcc.net/~physics/fla sh/LengthofDay.swf http://www.cs.sbcc.net/~physics/fla sh/LengthofDay.swf http://www.cs.sbcc.net/~physics/fla sh/LengthofDay.swf http://www.cs.sbcc.net/~physics/fla sh/LengthofDay.swf

7. Revolution – the elliptical motion of a body as it orbits another body in space.

8. The period of revolution for the Earth to revolve arou the sun is 365.25 days.

9. Kepler’s Laws of Motion 1 st Law –Planets orbit the sun in a closed curve called an ellipse.

10. 2nd Law –Planets seem to move faster when they are close to the sun and slower when they are farther away.

11. 3rd Law –Planets close to the sun orbit faster than planets far away from the sun.

12. Planets

13. Gravity – the attractive force of one object on another object. Newton’s Law of Universal Gravity

14. The strength of the gravitational force between two objects is dependant on two factors: 1.mass of the objects the more massive the object the greater the gravitational forcethe more massive the object the greater the gravitational force 2.the distance between the two objects the closer the objects are together, the greater the gravitational force between themthe closer the objects are together, the greater the gravitational force between them

15. The two biggest gravitational forces that we notice are: 1. 1.The sun (1.98892 x 1030 kg) is the most massive object in our solar system and exerts a huge gravitational force. This is why all the planets stay in orbit around the sun. 2. The Earth (5.9742 x 1024 kg) is so massive that its gravitational force keeps us from falling off the planet.

17. When astronauts go into space, they “float” because they are far enough away from the center of the earth that the gravitational force isn’t strong enough to hold them down.

19. OUT: Will a planet or comet be moving faster in its orbit when it is farther from or closer to the sun? Explain.