CHAPTER 1       WHAT IS PHYSICS?
        WHAT IS PHYSICS?  What do you think of when you think of physics?
Do you see equations?  Or bombs?  Or difficult material?
        Physics is the study of the most basic of concepts in nature.  It deals with the behavior and structure of matter.  It is a study of the rules of nature.  Without rules, science is pointless, for there can be no patterns and, thus, no future references.    Physics seeks to give you an understanding of and a way to predict (possibly) the outcome of activities occurring all around you.  If nothing else, it will encourage you to ask questions about the world around you.  This course in particular will be a hands-on class.  Every six weeks there will be a project to make that will adhere to guidelines.  In the handout you were given on the first day of class are the six projects for this year along with the due dates for them.  This will help you to preplan ideas for each project.  Perhaps you can even begin some early.  You will work in pairs on each project except the bridge.  There will also be on-the-spot constructions that you will prepare during a class period without notice ahead of time, so always bring your most creative mind to class.  
        Physics is the branch of knowledge that studies the physical world.  It studies everything from atoms to galaxies.  Physicists strive to explain how behaviors occur.  They study the natures of matter and energy and how they are related.  It is the most fundamental and all-inclusive of the sciences.  It is at the root of every field of science, and underlies all phenomena.  It is the present-day equivalent of what used to be called natural philosophy.  
        The feeling is that physics is at the bottom of all sciences.  Just above it is chemistry and at the top is biology.  
Sometimes the works of physicists are only of interest to other physicists or scientists.  Science which is studied for its own sake is called pure science.  It seeks only to answer theoretical questions. It has to do with discovering the true facts and relationships between observable phenomena in nature, and with establishing theories that serve to organize these facts and relationships.
Other times the work of scientists leads to devices, such as lasers, calculators, or computers.  This is called technology because it was devised with a purpose in mind.  This is a method of practical problem solving, which can create more problems as time goes on.  Technology has to do with tools, techniques, and procedures for implementing the finding of science.  
Physicists and all scientists generally use a method to approach any problem.  We will use the term strategy to indicate an organized approach to a problem that will break down the task.  Some strategies are listed:
        *List all possible solutions.
        *Look for patterns.
        *Construct a table, graph, or figure.
        *Make a model or a prototype.
        *Guess and check.
        *Work backwards.  Some of the problems that you will do will require                            this method.
        *Make a drawing.  This is also a very effective method with which to solve problems.  
        *Use unit analysis or conversion factors.  This is also a very good method to use when no solution is readily seen.  
        *Try formulating a mathematical equation to guide your thinking or to offer a shortcut to remembering relationships.

SCIENTIFIC METHOD
        Starting in the fourth and fifth centuries B. C., Greek philosophers tried to determine what the world was made of.   Aristotle, who lived around 340 B. C., was a student of Plato and tutored Alexander the Great, conqueror of much of the known world.  He and his followers made some observations of everyday occurrences and then tried to draw all possible conclusions about why specific events happened.  Unfortunately they did not investigate what happened or how it happened or even if it would happen again if circumstances were different.  
        Aristotle believed that all matter was made up of four elements:  earth, water, air, and fire.  Each element had a natural place.  The highest place belonged to fire, then air, then water, and then earth.  Motion only occurred because an element wanted to reach its own natural place.  Rest was matter’s natural state.  Motion could occur in two types:  violent and natural.  
        These ideas and others like them held for centuries until the sixteenth century, when Galileo Galilei claimed publicly that knowledge must be based on observations and experiments rather than ancient books.  Galileo imagined that if friction could be eliminated, an object would stay in motion forever.  He also doubted Aristotle’s view that objects of large mass fall faster than objects of small mass.  Galileo soon developed a systemic method of solving problems.  
        Galileo is known as the “Father of the Scientific Method”.  Modern research follows his method.  
                1.      Recognize a problem or observe a behavior.  
                2.      Hypothesize an answer.  A hypothesis is an educated guess about why a phenomenon occurred.  There are two types of hypotheses:  scientific and non-scientific.  Scientific hypotheses can be tested and proven right or wrong.  Non-scientific hypotheses have no such tests.  
                3.      Devise an experiment to test the hypothesis.
                4.      Research the literature to find laws that apply to the  behavior being observed.  Scientific facts may be found in this research.  These are close agreements by competent observers of a series of observations of the same phenomena.  These may be useful when devising a mathematical description, or law, of the behavior.  A law is a statement that has been found experimentally valid over a wide range of observed phenomena.  A less general, but similar, statement is a principle.
                5.      Formulate a conclusion that will explain the behavior.  
                6.      Generalize the conclusion so that a theory may be stated.  A scientific theory is a synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world.  It may never be proven beyond a shadow of doubt.  Only one experiment may prove it false.
A model may be used to help explain behaviors.  It might be a mental image or an analogy of the behavior in terms of something with which we are familiar.  It is usually simple whereas a theory is broader and more detailed.   

Although the scientific method is an organized approach to a problem, it has not been the key to most discoveries in science.  Trial and error, experimentation without guessing, accidental discovery, and other methods account for much of the progress in science.  Knowledge, creativity, skill, luck, imagination, and great patience also play large parts in discovery.   
        Progress in science has to do with attitude.  This attitude is one of inquiry, experimentation, and humility before the facts.  If a scientist holds an idea to be true, and finds any counter-evidence whatsoever, the idea is either modified or abandoned.  
        Scientists must accept facts openly even when the facts do not agree with their beliefs.  They must strive to separate what they see from what they want to see.  They must accept ideas from sources that are testable.  Speculations that are not testable must be disregarded.  A new theory may be adopted if it explains a larger range of phenomena.   
Copernicus’ heliocentric universe predicted astronomical occurrences with more accuracy than Ptolemy’s geocentric universe.  
        Progress in science excludes the human factor.  Scientists, who seek to comprehend the universe and know the truth with the highest degree of accuracy and certainty, cannot pay heed to their own or other people’s likes or dislikes, or to popular ideas about the fitness of things.  We can always ignore or refuse to believe science.  
        Progress in technology is not easy to refuse.  Here progress must be measured in human terms.  Technology can have no legitimate purpose but to serve people if it is to lead to a better world.  It is a way of solving practical problems.  
        When scientists try to solve a problem, many times they use a model.  It may be a small version of the observed phenomenon or an image or analogy that gives an approximate mental or visual picture of what is happening.  

MEASUREMENT AND UNCERTAINTY
        Scientists seek to find relationships between variables observed.  This requires quantitative measurements that are reproducible.  No measurement is absolutely precise; uncertainty always exists.  Estimated uncertainty is also called precision.  The percent uncertainty is calculated by the ratio of the uncertainty to the measured value multiplied by 100.  
Accuracy is defined as closeness to a true value.  It is dependent upon the quality of the measuring device.  It is based on only one measurement.  It can be compared by using percent error.
Precision is the closeness of a set of values and is not related to the accurate value.  It is dependent upon the skill of the person making the measurement.  Precise measurements may be made with a faulty instrument so long as the observer is consistent in his use of the instrument.  
Usually the uncertainty is assumed to be one or two digits in the last digit specified.  The digits that are reliably known are called significant figures.  The rule is to record all the numbers which can be read from an instrument plus one digit which is estimated.  What digits are significant?
All nonzero digits are significant.
All captive zeroes are significant.
All beginning zeroes are NOT significant.
All zeroes to the right of a nonzero digit and a decimal point are significant.
Ending zeroes in numbers without a decimal may or may not be significant.  The final significant zero may be noted with a bar over it.  
What about rules for doing operations with significant figures?
When adding or subtracting, the answer may have only as many DECIMAL PLACES as the least precise number in the operation.
When multiplying or dividing, the answer may have only as many SIGNIFICANT DIGITS as the least precise number in the operation.  

MATH
        Math is the language of physics.  It is unambiguous and understood by all.  
2  Algebraic solutions
3  Trigonometric functions
        a  sine
        b  cosine
        c  tangent
4  Graphs

UNITS, STANDARDS, AND THE SI SYSTEM
There are two kinds of measurement.  Both provide important information.  One kind of measurement is quantitative.  It gives results in numerical form.  It is objective because it requires an instrument.  The other kind of measurement is qualititative.  It gives results in a descriptive form.  It is subjective because it depends on the bias of the observer.   

Standards are agreements on sizes of certain quantities.  They are measures that eliminate controversies about quantities. They are comparisons of quantities.  They may be objects or phenomena that are of constant value and easy to preserve and reproduce.  

Different measuring systems are used throughout the world but, in science, the SI system is used exclusively.  It has only 7 fundamental units.  They are the meter, gram, second, candela, mole, ampere, and Kelvin.   All other units are derived from these.  Prefixes are used for very large and very small units in this system.  Equivalent units may be used as conversion factors to change from one unit to another.  
The meter is based on the distance light travels in a vacuum in 1/3x108 ths of a second.  
The second is based on the number of disintegrations from a cesium-133 atom.  
Prefixes are added to the base units to change the size of the unit.
Centigram  =  1/100 of a gram

Milligram =  1/1000 of a gram

Dekaliter  = 10 liters

Metric Prefixes

yotta  
Y
1024
yocto
y
10-24
zetta  
Z
1021
zepto
z
10-21
exa  
E
1018
atto
a
10-18
peta  
P
1015
femto
f
10-15
tera  
T
1012
pico
p
10-12
giga  
G
109
nano
n
10-9
mega  
M
106
micro
m
10-6
kilo
k
103
milli
m
10-3
hecto   
h
102
centi
c
10-2
deka  
da
101
deci
d
10-1


Conversion factors are used to change from one unit into another.  They come from equivalent quantities, such as 1 m = 100 cm.  Equivalent quantities may be written in one of two ways, 1 m/100 cm or 100 cm/1 m, depending on what unit is desired.

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