Chapter 4 - Chapter 4: Basic Physics Sir Isaac Newton...

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Unformatted text preview: Chapter 4: Basic Physics Sir Isaac Newton (lived 1641--1727) This chapter covers the revolutionary advancements due to probably the most brilliant scientist who ever lived: Isaac Newton . His greatest contributions were in all branches of physics. Kepler's discoveries about elliptical orbits and the planets' non-uniform speeds made it impossible to maintain the idea of planetary motion as a natural one requiring no explanation. Newton had to answer some basic questions: What keeps the planets in their elliptical orbits? On our spinning Earth what prevents objects from flying away when they are thrown in the air? What keeps you from being hurled off the spinning Earth? Newton's answer was that a fundamental force called "gravity" operating between all objects made them move the way they do. Newton developed some basic rules governing the motion of all objects. He used these laws and Kepler's laws to derive his unifying Law of Gravity. I will first discuss his three laws of motion and then discuss gravity. Finally, several applications in astronomy will be given. This chapter uses several math concepts that are reviewed in the mathematics review appendix. If your math skills are rusty, study the mathematics review appendix and don't hesitate to ask your astronomy instructor for help. Newton's Laws of Motion Motion In order to accurately describe how things move, you need to be careful in how you describe the motion and the terms you use. Scientists are usually very careful about the words they use to explain something because they want to accurately represent nature. Language can often be imprecise and as you know, statements can often be misinterpreted. Because the goal of science is to find the single true nature of the universe, scientists try to carefully choose their words to accurately represent what they see. That is why scientific papers can look so "technical" (and even, introductory astronomy textbooks!) When you think of motion, you may first think of something moving at a uniform speed. The speed = (the distance travelled)/(the time it takes). Because the distance is in the top of the fraction, there is a direct relation between the speed and the distance: the greater the distance travelled in a given time, the greater is the speed. However, there is an inverse relation between time and speed (time is in the bottom of the fraction): the smaller the time it takes to cover a given distance, the greater the speed must be. Units of speed involve (time unit)/(distance unit), like m/sec ("meters per second") or mile/hr ("miles per hour"), etc.m/sec ("meters per second") or mile/hr ("miles per hour"), etc....
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This note was uploaded on 04/22/2010 for the course BUS 255 taught by Professor Mcgee during the Spring '10 term at Aarhus Universitet.

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Chapter 4 - Chapter 4: Basic Physics Sir Isaac Newton...

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