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# notes%201 - Class notes #1 Engineering careers In our first...

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Class notes #1 Engineering careers In our first class we discussed engineering careers and some of the mechanical aspects of the class. This was for your information; none of it will be ‘on the test’. The four fundamental forces We discussed the four fundamental forces of classical physics: The strong force, responsible for holding together quarks in subatomic particles like the proton. The electromagnetic force, responsible for holding atoms together, as well as bonding atoms together into molecules, and molecules together into solids. This is the force that mediates the attraction between positive and negative charge, and is the basis for all of electrical engineering, from radio to computers. The weak force, responsible for holding the atomic nucleus together Gravity, the very weak force that nevertheless holds the stars and planets together, and keeps us from floating off into space. These forces differ in their strength (they are listed in stronger to weaker order above) and effective range. The strong and weak forces only act at very short ranges comparable to the size of an atomic nucleus and are of little relevance to our task at hand. Both the electromagnetic and gravitational forces act over large distances, and they also share some other common characteristics. The magnitude of the forces due to gravity, F g , and the static electric force, F e , are described by similar looking equations. Both depend inversely on the square of the distance, d , between the two bodies. Both contain a physical constant, G , for gravity, and for the electromagnetic force. Both also depend on the product of some physical property of the two bodies; the mass, m (measured in kilograms), for gravitation and the quantity of charge, q (measured in coulombs) , for the electrical force. A key difference is that mass is always positive, while charge can be either positive or negative. This has important implications: the gravitational force is always attractive, while the electrostatic

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## This note was uploaded on 10/21/2010 for the course ESE 123 taught by Professor Westerfield during the Fall '07 term at SUNY Stony Brook.

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notes%201 - Class notes #1 Engineering careers In our first...

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