Chapter 1: Introduction and Measurement

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Chapter 1 Introduction and Measurement

• Brent Royuk
• Phys-111Concordia University

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Foundations of Physics

• Before we consider what physics is, lets
  consider science in general.
• How would you answer the question What is
  science?

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The Scientific Method

• Define the question
• Gather information and resources
• Form a hypothesis
• Perform an experiment and collect data
• Analyze data
• Interpret data and draw conclusions that serve as
  a starting point for new hypotheses
• Publish results

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Problems with the Scientific Method

• Too procedural
• There really isnt a scientific method.
• the only principle that does not inhibit progress
  is anything goes. --Paul Feyerabend
• Deductive (general to specific) instead of
  inductive (specific to general)
• Individual experiments tend to be deductive, but
  a broad picture of the history and NOS is
  inductive.

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The Four Processes of Science

• From Gil Daenzer
• Observe Nature (Facts)
• Find Order (Laws)
• Build Models (Theories)
• Explain Predict
• This is a conceptual model for science, rather
  than a procedural one.

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The Four Processes of Science

• Example
• I saw a sunrise today (Fact)
• The sun rises in the east (Law)
• Whats the theory?

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The Four Processes of Science

• Example
• Drop a rock it falls (Fact)
• Things fall (Law)
• Whats the theory?

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Scientific Laws

• An observed regularity
• Laws are simple.
• Scientific laws are descriptive, not
  prescriptive.
• Scientific laws are discovered, not invented.
• God makes laws, not man.

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Some Well-Known Scientific Laws

• Boyles Law
• Charles Law
• Newtons Laws of Motion
• Keplers Laws of Planetary Motion
• Coulombs Law
• Ohms Law
• Maxwells Equations
• The Laws of Thermodynamics
• The Law of Definite Composition
• The Law of Conservation of Mass/Energy

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Scientific Theories

• A scientific theory is a well-substantiated
  explanation of some aspect of the natural world
  that can incorporate facts, laws, inferences, and
  tested hypotheses. --National Academy of
  Sciences
• Theories are the conceptual product of science
• God doesnt make scientific theories, we do.
• One-word synonyms Model, framework, explanation

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Some Well-Known Scientific Theories

• Relativity Theory
• Atomic-Molecular Theory
• Kinetic Theory
• Quantum Theory
• String Theory
• Grand Unification Theory
• Germ Theory of Disease
• Plate Tectonics
• Evolutionary Theory
• Evolutionary Psychology

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Problems with the Scientific MethodThe
Grade-School Scientific Certainty Myth

• Wrong
• Hypothesis
• Theory
• Law
• So a Law is a proven theory!

• Better
• Law
• Theory
• Hypothesis
• A theory is never proven.

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Discussion Activity

• Think of an example of some sort of everyday
  sequence in which an observable fact leads you to
  a law of some sort. Then formulate a theory that
  explains your law. Your law doesnt have to be
  scientific (dryers eat socks would be just as
  good as fire burns paper). In fact, it might
  be more fun if its humorous or relevant to
  everyday life.

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What is Physics?

• Old science
• Natural Philosophy
• The Queen of the Sciences
• Physics envy
• All science is either physics or stamp
  collecting. Ernest Rutherford
• ... it is impossible to explain honestly the
  beauties of the laws of nature in away that
  people can feel, without their having some deep
  understanding of mathematics. I am sorry, but
  this seems to be the case. Richard Feynman

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What is Physics?

• I know that this defies the law of gravity, but,
  you see, I never studied law. Bugs Bunny
• Physics is not difficult, it is just weird.
  Vincent Icke
• Chemistry is physics without thought.
  Mathematics is physics without purpose.
• If it wiggles, it's biology if it smells, it's
  chemistry if it doesn't work, it's physics.
• Physicists are simpleminded people.
• I can define that course in ______ words
• Topics

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Units of Measurement

• Standardization is necessary for science (the
  kings thumb)
• Cubits, Thumb inch, 12 inches foot, three
  feet yard
• 1793, French Academy of Sciences
• 1983 The distance light travels in
  1/299,792,458 second

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Units of Measurement

• The kilogram
• One cubic tenth of a meter of water
• The gram/milliliter/cc connection
• Prototype Pt-Ir cylinder

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Units of Measurement

• Where did the second come from?
• 1 sec 9,192,631,770 oscillations of Cs-133
  radiation
• The speed of time is one second per second.
• The MKS system vs. cgs, fps
• The liter
• The seven base units

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Units of Measurement

• USEFUL METRIC CONVERSIONS
• 1 million microphones 1 megaphone
• 1 million bicycles 2 megacycles
• 2000 mockingbirds two kilomockingbirds
• 10 cards 1 decacards
• 1/2 lavatory 1 demijohn
• 1 millionth of a fish 1 microfiche
• 453.6 graham crackers 1 pound cake
• 10 rations 1 decoration
• 10 millipedes 1 centipede
• 3 1/3 tridents 1 decadent
• 10 monologs 5 dialogues
• 2 monograms 1 diagram
• 8 nickels 2 paradigms
• 2 baby sitters 1 gramma grampa

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Units of Measurement

• Try these
• 3.4 cm ___ m
• 112000 ng ___ kg
• 340 g ___ kg
• 3.4 x 10-11 km ___ mm

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Dimensional Analysis

• Derived units can have funny dimensions
• e.g. 1 J1 kgm2/s2
• Sometimes you can decide if an equation is false
  if it doesnt work out dimensionally
• e.g.
• The books notation
• More informally, commonly
• You might also see a m/s2
• We will do math with units just like with numbers
• e.g. use vp/m to find v given p 12 kg m/s and m
  4.0 kg

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Converting Units

• These are all velocity units m/s, ft/s, mph,
  cm/min, cubits/week, attoparsecs/microfortnight
• All can be used interchangeably
• The conversion factor method
• 12 ft ___ yd
• 34 km/h ___ m/s
• 18 kg/m3 ___ slugs/ft3
• 1 mph ___ km/min
• At desk 1 mile/(min)2 ___ m/s2
• 1 apc/?fortnight ___ cm/s
• Fermi 1 microcentury equals about one lecture
  period

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Problem Solving
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Problem Solving

• Step-by-step procedure on p. 12
• We will use good problem solving form
• Write equation to be used
• Solve for desired quantity
• Substitute in knowns
• Give answer with units