PHYS2001_Ch. 1

# PHYS2001_Ch. 1 - PHYS2001 Physics 1 1.1 The Nature of...

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PHYS2001 – Physics 1 1.1 The Nature of Physics From the very big to the very small, Physics covers it all! This semester we will focus on Classical Mechanics – big things moving slowly (wrt the speed of light). Next semester you will study Electricity and Magnetism and Quantum Mechanics . Physics is the most fundamental of all the natural sciences. In science, there is only physics. All the rest is stamp collecting. - Earnest Rutherford The strength of Physics as a science is that all of the physical laws are based on experimental results. So why should you be required to take Physics ???

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Physics is like sex. It has practical applications, but that is not the main reason you do it. - Richard Feynman Our goal is to describe and explain how and why the world works the way it does. Through this process you will become analytical thinkers and effective problem solvers. Physics is the perfect vehicle for doing this. These are the skills you should take with you when you leave this course. What do we get with this knowledge??? Lasers Rockets Transistors Telecommunications Etc. All technology has its roots in Physics ! 1.2 Units Accurate measurements require precisely defined quantitative units. We are going to want to measure things like length , mass , and time .
There are several different systems of units used for measurement: SI – System International or MKS units (m eter, k ilogram, s econd) CGS (c entimeter, g ram, s econd) BE – British Engineering units (ft, slug, second) In this course we will use SI (MKS) units. Length = Meter (m) = Distance light travels in a vacuum in 3.3 ns (3.3 × 10 -9 s) Mass = Kilogram (kg) (1 kg ≡ 2.2 lbs. on the Earth’s surface) Time = Second (s) = The time it takes for 9,192,631,770 vibrations of a Cs-133 atom to occur 1.3 Converting Between Different Units and Base Units 1 km = 1000 m = 1 × 10 3 m 5.2 cm = 0.052 m = 5.2 × 10 -2 m If you need to brush up on powers of 10 or scientific notation, see Appendix A.

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Example My cat, Socola, is fat. He has a 17 in. waist. What is Socola’s waist size in m? To Do Unit Conversions: - Treat the units as algebraic quantities - Multiply by factors of “1” - Use the “mol method” 17 in. 1 in. 2.54 cm 1 m 100 cm = (17)(2.54) 100 = 0.43 m All of your answers must have appropriate units!!! Factors of 1 Significant Digits Every quantity (number) has a certain number of significant digits . These are digits in the number whose values are known with certainty. Mars Climate Orbiter (1999)!!!
For example, Socola is 27.25 cm tall, with the measurement uncertainty occurring in the 3 rd decimal place. Thus, all of these digits are significant (known with certainty), and 27.25 cm has 4 significant digits. If a zero is given as the last digit to the right of the decimal point, it is also significant. Example : 7.290 m has 4 significant digits. However, zeros immediately to the left of an unexpressed decimal point are not significant.

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## This note was uploaded on 09/22/2009 for the course PHYS 2001 taught by Professor Sprunger during the Spring '08 term at LSU.

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PHYS2001_Ch. 1 - PHYS2001 Physics 1 1.1 The Nature of...

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