ENGINE OF CHANGE

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Physics is fun!
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Physics 231Fall 2003
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Chapter 1Introduction, Measurement, Estimating
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1-1 The Nature of Science

• The principle aim of all sciences, including
  physics, is generally considered to be the search
  for order in our observations of the world around
  us.
• Science is a creative activity that in many
  respects resembles other creative activities of
  the human mind.
• Science is also intimately linked to all other
  aspects of life on Earth.

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The Nature of Science

• Physics is the most basic of all sciences.
• It deals with the behavior and structure of
  matter.
• The field of physics is generally divided into
  the areas of
• motion
• fluids
• heat
• sound
• light
• electricity and magnetism.

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Waves of Change

• The Third Wave, by Alvin Toffler, 1980

PRE FIRST WAVE HUNTER-GATHER SOCIETY
(gt 100,000 YEARS AGO - 8,000 B.C.)
100,000 YEARS
FIRST WAVE AGRICULTURAL SOCIETY
(8,000 B.C. - 1750 A.D.)
10,000 YEARS
SECOND WAVE INDUSTRIAL SOCIETY
(1750 - 1955)
200 YEARS
THIRD WAVE INFORMATION AGE SOCIETY
(1955 - ? )
? 100 YEARS
FOURTH WAVE BIO or NANO or ? TECHNOLOGY AGE?
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12-15 BILLION YEARS AGO
The Evolution of Society
SOLAR SYSTEM 4.5 BILLION Y.A.
HUNTER - GATHER SOCIETY ( ? - 8000 B.C.)
Homo Sapiens Sapiens
EVOL. OF LIFE
Homo Sapiens Neanderthalensis

• Fire
• Tools

(150,000-100,000 Y.A.)
(50,000 Y.A.)
THE BIRTH OF SCIENCE IN GREECE (580 B.C.-165 A.D.)
AGRICULTURAL REVOLUTION
AGRICULTURAL SOCIETY (8000 B.C. - 1750)
NEW STONE AGE
IRON
RENAISSANCE
BRONZE AGE
AGE
DARK AGES

• Birth of Universities (1100 - 1200)
• Printing Press (1450)
• Capitalism

(1400)
(4000 B.C.)
(8,000 B.C.)
(1500 B.C.)

• Greek Society
• Democracy

CLASSICAL SCIENTIFIC REVOLUTION
INDUSTRIAL SOCIETY (1750-1955)
(1750-1850)
(1543-1687)
NEWTONS LAWS
BIOTECHNOLOGY REVOLUTION
ELECTRONIC REVOLUTION
POST- INDUSTRIAL SOCIETY (1955 - 1992)
BIO or NANO or ? TECHNOLOGY AGE?

DNA
TRANSISTOR
1953
1992
1948
?
(1900-1927)
1955
THEORY
THEORIES
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1-2 Models, Theories, and Laws

• Science
• The scientific method
• Observations and Experiments
• Hypotheses
• Theories
• Laws
• Models
• Technology
• Society
• Paradigms

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Science

• Science is the process of discovering the order
  in the universe.
• Values of science
• Unwillingness to accept results solely on the
  basis of authority
• Willingness of scientists of each generation to
  build on the work of past scientists
• Insistence on the repeatability of experiments

THE SCIENTIFIC METHOD
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Elements of the Scientific Method

• Observations and Experiments
• Hypotheses
• Theories
• Laws

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Hypothesis

• AN HYPOTHESIS is an explanation that accounts
  for a set of data from observations and
  experiments. It is taken to be true for the
  purpose of argument or investigation.

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Theory

• A THEORY is devised to analyze, predict, or
  otherwise explain a set of data from observations
  and experiments. It is an organized set of new
  ideas (usually presented mathematically) based on
  laws, assumptions, and sometimes other theories.
  A theory is well grounded by observations and
  experiments.

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Law

• A LAW is a general statement about phenomena,
  of universal validity, whose basis rests on
  observations and experiments alone.

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Observations and Experiments

• An observation in science is the observation
  and measurement of a naturally occurring physical
  phenomenon. The results are called data.
  Examples are observations made of the other
  planets and stars.
• An experiment is a human-manufactured test to
  observe and measure phenomena, usually performed
  in a laboratory. It must be repeatable. The
  results are called data. An example is
  Galileos experiments in the free fall of objects.

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Observations and Experiments
I remember discussions with Bohr which went
through many hours till very late at night and
ended almost in despair and when at the end of
the discussions I went alone for a walk in the
neighboring park I repeated to myself again and
again the question Can nature possibly be so
absurd as it seemed to us in these atomic
experiments?
Warner Heisenberg Nobel Prize 1932
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Implications

• Science will never claim, for example, that
  evolution is a fact.
• Science says only At this time, the weight of
  evidence strongly supports the theory that
  evolution of the species did occur.
• Science acknowledges that, as more data is
  accumulated, this statement may either be
  reinforced or weakened.
• It is tempting to claim, as more and more
  positive data is reported, that a scientific
  statement is a fact.
• This is NOT so!

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Data vs. Facts
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Repeatability

• Repeatability of observations in science means
  that if you make an observation, you publish
  sufficient details about how you accomplished it,
  so that other researchers will be able to
  duplicate your observations.
• Repeatability of experiments in science means
  that you the researcher publishes sufficient
  details that another researcher can duplicate the
  experiment.

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Repeatability
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Peer Review

• Scientific results, whether theoretical,
  observational, or experimental, must be reported
  in a peer-reviewed scientific journal.
• The peer review process consists of other
  researchers in the field reviewing papers
  submitted for publication to see if they warrant
  it.
• The referees may accept the article, reject the
  article, ask for clarification, or ask for
  modifications.

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Peer Review

• Theoretical results must be detailed enough to
  allow the referees to follow all steps in the
  calculation.
• Observational or experimental results must
  contain enough detail to allow the referees to
  make a judgement as to the merits of the
  observation or experiment and for other
  researchers to repeat the observation or
  experiment to see if they get the same results.

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The Scientific Method
OBSERVATIONS AND EXPERIMENTS
HYPOTHESES
THEORIES
LAWS

• Observations and experiments must be Repeatable.
• Peer Review of publications is required.
• The scientific method uses both inductive and
  deductive logic.

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Data from Observations and Experiments
Other Theories
Laws of Physics
Assumptions
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The Power of a Theory
Computer Revolution
Transistor, LASER
Quantum Revolution
X-ray crystallography, Theory of chemical bonding
Biotechnology Revolution
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• BECAUSE IT WORKS
• Explaining the Universe
• Developing Technology

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Technology

• Technology is the use of tools, machines,
  materials, and energy to make life/work easier
  and more productive. It includes "how to."
• The integration of technology into society
  proceeds in three stages.
• Stage 1 technology is used to accomplish
  traditional tasks better.
• Stage 2 technology is used to do new things
  impossible to do without the new technology.
• Stage 3 a technology or a group of technologies
  creates a fundamental change in society.

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The S Curve
TECHNOLOGICAL ADVANCE
?
?
?
WHERE ARE WE TODAY?
TIME
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Technological Advance
?
CHANGE
1500
1600
1700
1800
1900
2000
TIME
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Exponential Growth
DNA MAPPING
TELEVISION
LASERS
COMMUNICATIONS
TRANSISTORS
THE INTERNET
COMPUTERS
MEDICINE
MANUFACTURING
BIG BANG MODEL
SPACECRAFT
OFFICES
LEISURE
NANOTECHNOLOGY
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Arthur C. Clarkes Three Laws

• First Law When a distinguished, but elderly
  scientist states that something is possible he is
  almost certainly right. When he states that
  something is possible he is probably wrong.
• Second Law The only way of discovering the
  limits of the possible is to venture a little way
  past them into the impossible.
• Third Law Any sufficiently advanced technology
  is indistinguishable from magic.

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Science Technology
SCIENCE
TECHNOLOGY
TECHNOLOGY ENGINEERING
PURE SCIENCE
APPLIED SCIENCE
SCIENCE FOR THE SAKE OF KNOWING
SCIENCE FOR A POTENTIALLY USEFUL
APPLICATION
TECHNOLOGY APPLIED TO SOCIETY FOR
PRACTICAL PURPOSES
EXAMPLES
EXAMPLES
EXAMPLES

• QUANTUM
• THEORY
• RELATIVITY
• THEORY
• COSMOLOGY
• SUPERSTRING
• THEORY

• TRANSISTOR
• GENETIC
• ENGINEERING
• HUMAN GENOME
• PROJECT

• INFORMATION
• TECHNOLOGY
• BIOTECHNOLOGY
• SPACESHIPS
• NOVEL MATERIALS

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WITHOUT SCIENCE THERE WOULD BE
VIRTUALLY NO MODERN TECHNOLOGY
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Science, Technology, and Society
PARADIGMS
Requests for Technology
Technology Support
TECHNOLOGY
SCIENCE

• Guidance
• Limits

• Technology to Improve Standards of Living
• New Paradigms

New Paradigms
SOCIETY
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The Idea of a Paradigm

• THE STRUCTURE OF SCIENTIFIC REVOLUTIONS, by
  Thomas Kuhn, 1962
• Kuhn defines a paradigm as a model or pattern
  it comes from the Greek paradeigma or para
  (alongside) deigma (to show)
• Normal science, according to Kuhn is done
  within the prevailing scientific paradigms.
  Normal science is a communal activity guided by a
  group of shared models and assumptions.
• Marilyn Ferguson, in her book The Aquarian
  Conspiracy, (1970) expanded the definition as a
  scheme for understanding and explaining certain
  aspects of reality...A paradigm shift is a
  distinctly new way of thinking about old
  problems.

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Example From Physics
ARISTOTLE/ PTOLEMY (EARTH-CENTERED UNIVERSE)
Paradigm Completely Rejected
GALILEO, NEWTON, et al. (SUN-CENTERED, CLOCKWORK
UNIVERSE)
Paradigm Absorbed as an Approximation
EINSTEIN (SPECIAL AND GENERAL RELATIVITY)
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Characteristics of Paradigms

• They are hierarchical.
• They are common.
• They sometimes keep us from solving problems --
  paradigm paralysis.
• Outsiders (to the problem area) are sometimes
  better at creating new paradigms they do not
  have a vested interest.
• Old and very young practitioners have to be
  courageous to join a new paradigm early in its
  development.
• You can choose to change your paradigm.

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Paradigm is a Hierarchical Concept
TOP-LEVEL WORLD VIEW
CULTURAL
GEOGRAPHICAL
POLITICAL
WORK-BASED
FAMILY
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Models

• Useful tool for understanding
• Mental image of a phenomena in terms of something
  with we are familiar
• Gives approximate mental or visual picture when
  we cannot actually see something happening

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Logic

• The scientific method uses both deduction and
  induction.
• DEDUCTION (reasoning from a general principle to
  a specific conclusion)
• Correct conclusions depend upon
• The validity of the premises (Note premises
  often come from inductive logic.)
• Valid logic
• INDUCTION (reasoning from many specific pieces of
  data to a general principle)
• Correct conclusions depend upon
• The accuracy of the data
• Valid assumptions
• Valid logic
• The quantity of data (statistics)

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1-3 Measurement and Uncertainty Significant
Figures

• Uncertainty
• No measurement is absolutely precise (remember
  discussion on data?)
• Uncertainty arises from different sources.
• Outright mistakes
• Limited accuracy of measuring apparatus
• Systematic errors
• Random errors
• When giving the result of a measurement it is
  important to state the precision or estimated
  uncertainty.
• Percent uncertainty is the ratio of the
  uncertainty to the measured value.

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Uncertainty

• What is the percent uncertainty in the
  measurement 3.26 0.25 m?
• Answer uncertainty
• (0.25 m)/(3.26 m)x100 7.7
• What, approximately, is the percent uncertainty
  for the measurement given as 1.28 m?
• Answer We assume an uncertainty of 1 in the
  last place, i.e., 0.01, so we have
  uncertainty
• (0.01 m)(1.28 m)x100 0.8. Because the
  uncertainty has 1 significant figure, the
  uncertainty has 1 significant figure.

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Error Calculation for Labs
Accepted Value Experimental Value
Error (100)
Accepted Value
Accepted value may be the value of a physical
constant, for example g 9.8 m/s2, or a
theoretical calculation.
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Significant Figures

• The number of reliably known digits in a number
  is called the number of significant figures.
• Thus, there are four significant figures is the
  number 23.21 cm and two in the number 0.062 cm
  (The zeros in the latter only count for place
  holders that show where the decimal point goes.
• The number of significant figures may not always
  be clear.
• Take, for example, the number 80. Are there one
  or two significant figures?

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Significant Figures

• If we say about 80 km between two cities, there
  is only one significant figure.
• If we say there are exactly 80 km within an
  accuracy of 1 or 2 km, then 80 has two
  significant figures.
• The rule is the final result of a
  multiplication or division should have only as
  many digits as the number with the least
  significant figures used in the calculation.

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Scientific Notation

• Also known as powers of ten notation.
• For example we write 36,000 as 3.6 x 104
• Or 0.0021 as 2.1 x 10-3
• 100 ?

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We will use these.
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Conceptual Example 1-1

• Is that diamond yours?
• A friend asks to borrow your precious diamond
  for a day to show her family. You are a bit
  worried, so you carefully have your diamond
  weighed on a scale which reads 8.17 grams. The
  scales accuracy is claimed to be 0.05 grams.
  The next day, you weigh the returned diamond
  again, getting 8.09 grams. Is this your diamond?

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1-4 Units, Standards, and the SI System

• Systems of Units Systeme International (SI)
  (French for International System) is the
  international standard system.
• KGS (most often used)
• Length meters (m)
• Time seconds (s)
• Mass kilograms (kg)
• Force newton (N)
• CGS
• Length centimeters (cm)
• Time seconds (s)
• Mass grams (g)
• Force dyne

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Units, Standards, and the SI System

• British Engineering System
• Length foot (ft)
• Time second (s)
• Mass slug
• Force pound (lb)

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Base vs. Derived Units

• Physical quantities can be divided into two
  categories base quantities and derived
  quantities.
• A base quantity must be defined in terms of a
  standard.
• Scientists, in the interest of simplicity, want
  the smallest number of base quantities possible
  consistent with a full description of the
  physical world.
• This number turns out to be seven, given in table
  1-5.

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Base vs. Derived Units

• All other quantities are defined in terms of
  these seven base quantities, and hence are
  referred to as derived quantities.
• An example of a derived quantity is speed which
  is defined as the distance traveled divided by
  the time it takes to travel that distance. In
  the KGS system this is meters per second (m/s).
• To define any quantity, whether base of derived,
  we can specify a rule or procedure, and this is
  called an operational definition.

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1-5 Converting Units

• Any quantity we measure, such as length, a
  speed, or an electric current consists of a
  number and a unit.
• Often we are given a quantity in one set of
  units, but we want it expressed in another set of
  units.
• Then we must use a conversion factor.
• For example, a convenient factor to keep in mind
  is 1 in. 2.54 cm.
• In this course, we will almost always use the
  KGS system.

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Example 1-2

• The 100-m dash.
• What is the length of the 100-m dash expressed
  in yards?

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Example 1-3

• Area of a semiconductor chip.
• A silicon chip has an area of 1.25 square
  inches. Express this in square centimeters.

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Example 1-4

• Speeds.
• Where the posted speed limit is 55 miles per
  hour (mi/hr or mph), what is this speed (a) in
  meters per second (m/s) and (b) in kilometers per
  hour (km/h)?

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1-6 Order of Magnitude Rapid Estimating

• We are sometimes interested only in the
  approximately value of a quantity.
• A rough estimate can be made by rounding off all
  the numbers to one significant figure and use its
  powers of ten.
• Such an estimate is called an order-of-magnitude
  estimate, or more informally a back-of-the-envelo
  pe calculation.

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Example 1-5

• Volume of a lake.
• Estimate how much water there is in a particular
  lake, which is roughly circular, about 1 km
  across, and you guess it to have an average depth
  of about 10m.

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Example 1-6

• Thickness of this page.
• Estimate the thickness of a page of this book.

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Example 1-7

• Height by triangulation.
• Estimate the height of the building shown in the
  figure by triangulation, with the help of a
  bus-stop pole and a friend.

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Example 1-8

• Estimating the radius of the Earth.
• An easy way to convince yourself that the Earth
  is round is to watch a ship at sea disappear over
  the horizon on a calm day. In fact, believe it
  or not, you can estimate the radius of the Earth.
  Suppose you measure the deck of a large sailboat
  moored on a lake or a bay to be 2.0 m above water
  level. Then you go to the far side of the lake,
  where you are 4.4 km from the sailboat. Now you
  lie down right at the waters edge and you
  estimate that you can see only the upper ¼ of the
  sailboats hullthat is, ¾ of the hull, or 1.5 m,
  is below the horizon (hidden behind the water).
  Using the figure, where h 1.5 m, estimate the
  radius of the Earth.

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1-7 Dimensions and Dimensional Analysis

• When we speak of the dimensions of a quantity, we
  are referring to the type of units or base
  quantities that make it up.
• The dimensions of an area, for example, are
  always length squared, abbreviated L2
• Note the number of items is not a unit and has no
  dimensions. Hence, the number of atoms or
  molecules has no dimensions.
• Dimensions can be used to help in working out
  relationships, and such a procedure is referred
  to as dimensional analysis.

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Homework Problem 1

• The age of the universe is thought to be
  somewhere around 10 billion years. Assuming one
  significant figure, write this in powers of ten
  in (a) years, (b) seconds.

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Homework Problem 2

• How many significant figures do each of the
  following numbers have (a) 2142, (b) 81.60, (c)
  7.63, (d) 0.03, (e) 0.0086, (f ) 3236, and (g)
  8700?

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Homework Problem 3

• Write the following numbers in powers of ten
  notation (a) 1,156, (b) 21.8, (c) 0.0068, (d)
  27.635, (e) 0.219, and (f ) 22.

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Homework Problem 8

• Multiply 2.079 x 102 m by 0.072 x 10-1, taking
  into account significant figures.

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Homework Problem 9

• Add 9.2 x 103 s 8.3 x 104s 0.008 x 106 s.

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Homework Problem 19

• A typical atom has a diameter of about 1.0 x
  10-10 m. (a) What is this in inches? (b)
  Approximately how many atoms are there along a
  1.0-cm line?

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Homework Problem 23

• A light-year is the distance light (speed
  2.998 x 108 m/s) travels in one year. (a) How
  many meters are there in 1.00 light-year? (b) An
  astronomical unit (AU) is the average distance
  from Sun to Earth, 1.50 x 108 km. How many AU
  are there in 1.00 light-year? (c) What is the
  speed of light in AU/h?