Lecture01

# Lecture01 - Physics 344 Foundations of 21 st Century...

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Unformatted text preview: Physics 344 Foundations of 21 st Century Physics: Relativistic and Quantum Systems Instructor: Dr. Mark Haugan Office: PHYS 282 [email protected] TA: Dan Hartzler Office: PHYS 7 [email protected] Grader: Fan Chen Office: PHYS 222 [email protected] Office Hours: If you have questions, just email us to make an appointment. We enjoy talking about physics! Physics 344 Foundations of 21 st Century Physics: Relativistic and Quantum Systems In Physics 172(H) and 272(H) you learned a lot about how the Universe works by engaging in two intertwined processes central to science. This semester we will use them to learn. In one, we reflect on our observations of natural phenomena and on the results of experiments to identify what we believe to be fundamental constituents of the Universe and fundamental principles that govern their behavior. For example, early on, we thought about motions of particles near some other fixed object and decided that changing particle velocity was a fundamental indicator that a particle is interacting with another object. Our first fundamental principle, Newtons First Law of Motion, expressed this conclusion. An object moves in a straight line at a constant speed except to the extent that it interacts with other objects. We have been building on that initial insight ever since. We developed the fundamental concepts of momentum and force and the Momentum Principle so that we could predict and explain particles changing velocities quantitatively. sys net dp F dt = a a The time rate of change of a systems momentum is equal to the net force exerted on it by objects in its surroundings. , , , sys sys f sys i net p p p F t - = a a a a When considering a time interval t short enough that the net force is essentially constant during the interval, this is equivalent to a form of the Momentum Principle that we used often in previous courses. The way in which we use the Momentum Principle to predict and explain particle motions is an example of the second process central to science that we mentioned earlier. In that other process we use our fundamental concepts and principles to construct physical models of complex real-world systems to predict and explain their behavior. Weve seen in previous classes that we can explain and understand a remarkably wide variety of phenomena in this way. Before we examine an example of this kind of analysis, note that our two processes really are intertwined. The understanding we develop by modeling new physical situations influences our subsequent reflection on what is or is not fundamental. Our collection of fundamentals evolves and grows as we learn. It did when we introduced the electromagnetic field as a new fundamental constituent of the Universe and developed new fundamental principles in the form of Maxwells equations and the Lorentz force law to help us better understand electric and magnetic interactions between charged particles....
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## This note was uploaded on 12/09/2011 for the course PHYS 344 taught by Professor Garfinkel during the Fall '08 term at Purdue.

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Lecture01 - Physics 344 Foundations of 21 st Century...

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