What are some examples of Kepler's ideas towards motion and force?

What were some of his ideas about the motion on the planets.??

Help its for my school project and i dont know anything :(

Thanks for any help :]What are some examples of Kepler's ideas towards motion and force?Kepler had several laws describing the motion of planets. His laws were based on observation, but can be proven with motion laws and calculus. His laws only hold strictly true for the situation of 1 body orbiting another body of much larger mass. For instance 1 planet orbiting 1 star. It also must be true that the size of the smaller body must be negligible compared to the size of the orbit.



Law 1: Orbital motion is elliptical, with the larger body at one of the two foci of the ellipse.

Law 2: The square of the total orbital period is proportional to the cube of the semimajor axis of the ellipse

Law 3: The line joining the two bodies will sweep out equal areas in equal time.



Interpretation of laws:

Law 1: Orbital motion will result in an elliptical path of the smaller body. Ellipses have two special points called foci, and the larger body will lie at one of them. In a special case, the orbit can be circular, with the larger body lying at the center. You might want to read up on the geometry of ellipses. Even learning how to draw an ellipse with two thumbtacks, a string and a pencil, would be good for this project.



Law 2: What is a semimajor axis? Well, it is kind of like the largest radius of the orbit. If the orbit is perfectly circular, it is the radius. Because of this law, there is a direct relationship between the solar distance to a planet and the length of its year. Try looking up data for solar distances and year length, and confirm that they match this theoretical trend. Why might they not match exactly? What are sources of error when applying Kepler's laws to our solar system?



Law 3: I know a funny joke about this one, see the following comic

http://xkcd.com/21/



What does it mean? This is how we understand when a planet moves slowest (when furthest from the sun), and when a planet is moving fastest (closest to the sun). Either way, the area traced out by the wedge connecting the sun to the planet's daily path, will always have the same area.

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As for project ideas, you tell me that you don't have any after reading my descriptions. I've slipped in two, one which is good for college students, one which is good for high or middle school students. As for others, it depends your grade level and how much else you'd like to learn.