schab lecture 1(2)
TRANSCRIPT
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Conceptual Physics
PHY 103
Professor Schab
Lecture1:
About Science
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What is Science?
Science is a logical and rigorous method
used to investigate the
world around us.
Science has specific rules that guide
this investigation.
Science gives specific meanings to some common words:
theory, force, speed, etc.
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Scientific Measurements
Measurements
relate to how much you know
about something.
of pinhole images of the Sun
nicely lead to a calculation
of the Suns diameter.
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Measurements can be defined in
many ways.
In the US, we use the English(Imperial) System: units such as
miles, pounds, gallons, etc.
In the rest of the world, the metr ic systemis used.
When doing science, everyone has to agree on a system.
Measurements
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Scientific Notation
In science, we use numbers that are very small and very large.
16x1074.600000006740000000
-11x104.3340000000000.
Writing out numbers such as 67400000000000000 or
.000000000034 is cumbersome and hard to read.
So scientists use Scienti f ic Notation.
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Common Metric Prefixes
310001.01000
1milli 21001.0100
1centi
3101000kilo 6101000000mega
9101000000000giga
24100000000000000001000000000yotta
And the not so common...
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Multiple Prefix Symbol Common Name
(10100)100 anton A antonplex
(1010)100 - - googolplex
10100 - - googol
1024
yotta Y heptillion
1021 zetta Z hexillion
1018 exa E quintillion
1015 peta P quadrillion
1012 tera T trillion
109 giga G billion
106 mega M million
103 kilo k thousand
102 hecto h hundred
101 deca da ten
10-1 deci d tenth
10-2 centi c hundreth
10-3 milli m thousandth
10-6 micro (Greek mu) millionth
10-9 nano n billionth
10-12 pico p trillionth
10-15 femto f quadrillionth
10-18 atto a quintillionth
10-21 zepto z hexillionth
10-24 yocto y heptillionth
Decimal
Prefixes and
Multiples,
Powers of Ten
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Science uses the International System of Units: SI. This system
defines certain basic properties that every other measurement
depends upon. It is basically the metric system.
The basic units chosen must be easy toduplicate anywhere in the world.
Units
Units are every bit as important as the numbers.
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Consistency
It is VERY important to keep unitsconsistent.
If you mix up systems, for
example, using miles with kilograms,you will get wrong answers!
When doing calculations, the units are
every bit as important as the numbers.
Ask NASA! They lost a 250 million dollar Mars spacecraft
because of mixed up units!
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Time
Time is a fundamental property of
the universe.
Time is subjective for humans.Science requires a common,
unchanging value.
The second is the duration of 9,192,631,770 periods of the radiation
corresponding to the transition between the two hyperfine levels of
the ground state of the cesium-133 atom.
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Length
Length in the MKS system is defined as the meter.
The meter is the length of the path traveled by light in vacuum during
a time interval of 1/299 792 458 of a second.
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Mass
Mass measures the amount of matter an object contains. It is NOTthe same thing as weight!
Mass is measured in kilograms.
The kilogram is defined by the mass of the international prototype of
the kilogram stored in Paris.
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The Scientific Attitude
The scientific attitude is one of
inquiry.
experimentation.
willingness to admit error.
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The Scientific Attitude
Scientists
are experts at changing their minds.
must accept experimental findings
test for erroneous beliefs
understand objections and positionsof antagonists.
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Hypothesis
Hypothesis: An educated guess; a
reasonable explanation of an observation
or experimental result that is not fully
accepted as factual until tested over andover again by experiments.
A hypothesis is an educated guess about
how things work: "If _____[I do this]_____, then _____[this]_____ will
happen."
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Fact
Fact: a statement about the world that competent
observers who have made a series of observations
agree on.
A fact is not immutable and absolute, but is generally a
close agreement by competent observers of a series of
observations of the same phenomena. The observations
must be testable.
Since the activity of science is the determination of the
most probable, there are no absolutes.
Facts that were held to be absolute in the past are seen
altogether differently in the light of present-day
knowledge.
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Scientific Law
Law (principle: a general hypothesis or
statement about the relationship of natural
quantities that has been tested over and
over again and has not been contradicted.
A scientific law can often be reduced to a
mathematical statement, such as F=ma;
it's a specific statement based on empiricaldata, and its truth is generally confined to
a certain set of conditions.
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Scientific Theory
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's generally -- though by no means always -- a
grander, testable statement about how nature
operates.
You can't necessarily reduce a scientific theory
to a pithy statement or equation, but it does
represent something fundamental about how
nature works.
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Scientific Theory
The theory can be refined, or with new
information it can take on a new direction.
It is important to acknowledge the
common misunderstanding of what a
scientific theory is, as revealed by those
who say, But it is not a fact; it is only a
theory.
Many people have the mistaken notion
that a theory is tentative or speculative,
while a fact is absolute.
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The Scientific Method is a logical and rational
order of steps by which scientists come to
conclusions about the world around them. The Scientific Method helps to organize
thoughts and procedures so that scientists can
be confident in the answers they find. Scientistsuse observations, hypotheses, and deductions to
make these conclusions.
What is the Scientific Method?
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The steps of the Scientific Method are:
Observation/Research
Hypothesis Prediction
Experimentation
Conclusion
What is the Scientific Method?
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1. The observation is done first so that you knowhow you want to go about your research.
2. The hypothesis is the answer you think you'll
find.
3. The prediction is your specific belief about thescientific idea: If my hypothesis is true, then I
predict we will discover.....
4. The experiment is the tool that you invent to
answer the question.
5. The conclusion is the answer that the experiment
gives.
What is the Scientific Method?
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Science, Art, and Religion
Comparison of science, art, and religion by
domain:
Science is of the natural order and involves
the discovery and recording of natural
phenomena.
Art is the interpretation and expression of
human experience. Religion involves faith and worship of a
supreme being.
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Science and Technology
Science is concerned with gathering and
organizing knowledge.
Technologyis the use of scientific
knowledge for practical purposes and to
provide tools for further exploration.
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Errors in Experiments
Error in experiments have several sources.
First, there is error intrinsic to instruments of
measurement.
Second, there is non-random or systematicerror, due to factors which bias the result in one
direction.
No measurement, and therefore no experiment,can be perfectly precise.
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Random Error
There is error intrinsic to instruments of
measurement.
Because this type of error has equal
probability of producing a measurement
higher or lower numerically than the "true"
value, it is called random error.
Random errors can be reduced by
averaging a large number of
measurements.
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Systematic Error
There is non-random or systematic error, due tofactors which bias the result in one direction.
A reproducible discrepancy between the result
and "true" value that is consistently in the same
direction
Systematic error is sometimes called "bias" and
can be reduced by applying a "correction" or
"correction factor" to compensate for an effectrecognized when calibrating against a standard.
Unlike random errors, systematic errors cannot
be reduced by increasing the number of
observations.
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Accuracy versus Precision
Accuracy is how close a measured value
is to the actual (true) value.
Precision is how close the measured
values are to each other.
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Review Questions
S f
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a. guide to improving human behavior.
b. recipe for avoiding conflicts.
c. process for finding connections in nature.
d. handbook for establishing truth.
Science is an organized body of
knowledge about nature and also a
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The size of the Moons shadow on
Earth is
a. smaller than the size of the Moon.
b. about the same size as the Moon.
c. larger than the size of the Moon.
d. incapable of being observed.
Th i f b th th M d th
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a. both have the same diameters.
b. both are at about the same distance from
Earth.c. the smaller Moon is closer to Earth than the
Sun.
d. both the Moon and the Sun circle Earth.
The sizes of both the Moon and the
Sun are the same in the sky, which
indicates that
Th i f th i f th S
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The size of the images of the Sun
on a sidewalk beneath a sunlit tree
depends ona. the size of the openings between leaves
above.
b. whether or not the openings between leavesare circular.
c. the distance between the sidewalk and the
openings between leaves above.
d. how close the location is to the equator.
A h th t l
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A person who says, thats only a
theory likely doesnt know that a
scientific theory is aa. guess that involves many facts.
b. hypothesis of sorts.
c. vast synthesis of well-tested hypotheses andfacts.
d. guess that may or may not be factual.
M i t t th t t f
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More important than a test for
proving a hypothesis right is a test for
a. knowing full well that it is right.
b. proving more than one way that it is right.
c. proving it wrong.d. elevating it to a scientific theory.
Whi h f th i i tifi
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Which of these is a scientific
hypothesis (that could be proved
wrong)?a. Atoms in proper proportions make us feel good.
b. Atoms are in all the stars in the universe.
c. An atom is the smallest bit of matter in amaterial.
d. Distant galaxies have atoms not found on Earth.
A strength of science is that
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A strength of science is that
scientific theories
a. are fixed.
b. can change with new data.
c. are the hypotheses of brilliant people.d. are verifiable.
A fact in science is something that
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A fact in science is something that
a. is forever true.
b. may change over time.
c. cannot be denied.d. agrees with ancient records.
Science is concerned mainly
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Science is concerned mainly
with the
a. natural world.
b. spiritual world.
c. difference between right and wrong.d. search for eternal truths.