Chapter Notes
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n Galileo Galilei, Tycho Brahe, and Johannes Kepler were contemporaries. n They followed the work of Nicolaus Copernicus. n Newton built upon all of this previous work and, as he said, "I stood on the shoulders of giants". |
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| Galileo Galilei | |||
| 1564-1642 | |||
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| Nicolaus Copernicus | Tycho Brahe | Isaac Newton | |
| 1473-1543 | 1546-1601 | 1642-1726 | |
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| Johannes Kepler | |||
| 1571-1630 |
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Said Another Way Observe Guess what is happening - laws, etc an construct a model* See if you can predict what you see with the model If you can, then model is ok for now If not, then you must modify the model *The problem with models - do not be fooled by them! |
Apparent movement back and forth of the planets
There are two special points F1 and F2 on the ellipse's major axis, on either side of the center, such that the sum of the distances from any point of the ellipse to those two points is constant and equal to the major diameter . Each of these two points is called a focus of the ellipse.
http://mathworld.wolfram.com/Ellipse.html
First Law
The path of the planets about the sun are elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses)
Second Law
An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time.
(The Law of Equal Areas)
Third Law
The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun.
(The Law of Harmonies)
- First law
- There exists a set of inertial reference frames relative to which all particles with no net force acting on them will move without change in their velocity. This law is often simplified as "A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force." Newton's first law is often referred to as the law of inertia.
- Second law
- Observed from an inertial reference frame, the net force on a particle of constant mass is proportional to the time rate of change of its linear momentum: F = d(mv)/dt. When the mass is constant, this law is often stated as, "Force equals mass times acceleration (F = ma)": the net force on an object is equal to the mass of the object multiplied by its acceleration.
- Third law
- Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence, "To every action there is an equal and opposite reaction."