ch12_esit

= = = __ Universal Gravitation __ =

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__ 12.1- The Falling Apple __
Isaac Newton was the man who came up with the idea of gravity. According to a famous legend, the idea occurred to him while he was sitting under an apple tree on his farm. Newton under stood the concept of inertia developed by Galileo. Newton also knew that without an outside force, moving objects continue to move at a constant speed in a straight line and if an object undergoes a change in speed or direction then a force is responsible.

__ 12.2 The Falling Moon __
Newton then realized that if the moon did not fall it would move off in a straight line and leave its orbit. His idea was that that the moon is falling around the earth. He stated that the moon was simply a projectile circling the earth under the attraction of gravity. The distance that the moon falls is about 1.4mm every second.



__ 12.3 The Falling Earth __
Just like the moon the earth and all of the other planets are constantly falling around the sun. If they ever stop they will fall off in a straight line. Newton's law of gravitation confirmed the Copernican theory of the solar system. The earth was NOT the center of the universe. The Planets don’t crash into the sun because they have tangential velocities.

__ 12.4 Newton's Law of Universal Gravitation __
The law states that: every object attracts every other object with a force that for any two objects is directly proportional to the mass of each object. This law can be expressed symbolically as: F~m1m2/d^2 m1= mass of one object m2= mass of the other object d= distance between their centers of gravity the greater the masses the greater the forces. The greater the distance between the objects, the weaker the force of attraction.

** F= G m1m2/d^2  **
The force of gravity between 2 objects can be found by multiplying their masses, dividing by the square of the distance between their centers, then multiplying by constant G. G= 6.67 X 10^ -11 Nm^2/kg^2 The force the earth exerts on a mass of 1 kilogram at its surface is 9.8 Newton’s.

__ 12.5 Gravity and Distance: The inverse square Law __
The inverse square law says that when the enery is doubled the outcome force will be 1/4. When the energy is tripeld the out come force will be 1/9. Examples of where the square law applies are: Light, Radiation, and sound. The further away an object is from the center of the earth the less it will way. No matter how far away you get from the earth it will NEVER reach 0.

__ 12.6 Universal Gravitation __
The reason the earth is round is because of gravity. Beofre the earth became soild it had already attracted is self together and any corners that may have been created were pulled into the middle.  The earth is thought be have been formed by the “big bang” theory about 10 to 15 billion years ago. This theory consisted of all of the matter in the universe being thrown outward from this explosion and continued to go outward. On the other hand when an object is fired outward at some point it will start to come back from where it was thrown. This theory is called the “big crunch” which would all of the planets being sucked back together.
 * Perturbation-** The deviation of an orbiting object from its path around a center of force caused by the action of an additional center of force.