Transcript Chapter 1 Physics, the Fundamental Science I. The Scientific Enterprise

Chapter 1 Physics, the Fundamental Science
I.
The Scientific Enterprise
A.
Developing Scientific Explanations (Rainbow)
1) Look it up
a) “Appeal to Authority”
b) Scientists do this all of the time
c) Depends on someone else’s work
2)
Invent your own explanation: Educated Guess
a) Use your common sense
b) Use what you know about other phenomena
3)
Do some tests to see if your idea is right
4)
Change your ideas or decide that they seem correct
5)
Talk about what you saw or did with others
B. The Scientific Method
1) Careful observation of natural phenomena
2) Formulation of testable rules based on experience
3) Develop hypothesis to explain the observed rules
4) Test the hypothesis by experiment
5) Communicate with others
C. Definitions
1) Emperical Law: generalization derived from observation
2) Hypothesis: educated guess at the explanation of a problem
3) Theory: testable organized knowledge explaining a part of nature
D.
Using Scientific Method on an Everyday Phenomena
1) Observe: don’t do well on first several assignments in a class
2) Hypotheses
3) Experiment
4) Communicate
Scope of Physics
II. Where does Physics fit in Science?
A.
Physical Sciences: physics, chemistry, geology, astronomy, meteorology
1) Physics: study of the basic nature of matter and the interactions that
govern its behavior
2) Chemistry: study of composition, structure, and reactions of the various
forms of matter
B.
Life Sciences:
1) Biology: study of living organisms and life processes
2) Health Sciences: study of determining and maintaining wellness
C.
Size of Matter studied
1) Physics: smaller than atoms, bigger than molecules
2) Chemistry: atoms and molecules
3) Biology: collections of living molecules
D. Subfields of Physics
1)
Classical Physics: well developed before 1900
a) Mechanics: forces and motion (ball in flight)
b) Thermodynamics: temperature, heat, and energy (melting of ice)
c) Optics: light (lenses)
d) Electricity and Magnetism: forces and current (circuits)
2)
Modern Physics: greatest development after 1900
a) Atomic Physics: structure/behavior of atoms
b) Nuclear Physics: atomic nuclei
c) Particle Physics: subatomic particles
d) Condensed Matter Physics: solids/liquids
3)
Related to
Chemistry
Applied Physics: using physics to solve everyday problems
Also known as Engineering
III. Math and Physics
A.
Why is there so much math in physics?
1) Math is a compact way to express physics ideas
2) But, most physics ideas can be discussed with words too!
3) This class will use Algebra and basic math but the ideas are most important
B.
Measurements
1) Physicists use measurements (experiments) to test their hypotheses
2) Units: physical quantities are meaningless without units
C.
Proportions
Example: A recipe for 3 people uses 1 cup of millk. How much milk is needed for
4 people?
-Words: the quantity for 4 is the same ratio as the ratio of 4 people to 3 people
-Math: Q 4  4  Q   4 Q  Q   4 (1 cup)  4 cups
4
3
4
Q3 3
3
3
3
-Units: answer is meaningless without them (4/3 milk?, 4/3 people?)
D.
Dimensional Analysis
1) Also known as canceling units (Doing Algebra on units)
2) This is the key step to solving many of the problems in the course
3) Example: How many seconds are in one year?
 60s  60m
  24h  365d  100y






  h  d  y  century
 m
E.

  3,153,600,000 seconds/ce ntury

Scientific Notation: Appendix B
1) Present very large and very small numbers compactly
a) 3,153,600,000 = 3.1536 x 109
b) 0.000000025 = 2.5 x 10-8
2) Addition and Subtraction
a) Write compacted numbers out or use a calculator
b) Example: 5.36 x 104 + 4.02 x 10-3 = ?
3)
53,600
+
0.00402
53,600.00402
Multiplication and Division
a) Multiplication: multiply the numbers and add up the exponents
(3 x 106) x (2 x 10-4) = 6 x 102
b) Division: divide the numbers and subtract the exponents
(9 x 106) x (3 x 10-4) = 3 x 1010
F. Metric System
Giga
1,000,000,000 1 x 109
1 billion
3 Gb hardrive
Mega
1,000,000
1 x 106
1 million
1.4 Mb floppy
Kilo
1,000
1 x 103
1 thousand
10 Km
centi
100
1 x 10-2
1 hundredth
5.0 cm
milli
0.01
1 x 10-3
1 thousandth
452 mg
micro
0.000001
1 x 10-6
1 millionth
27 ms
0.000000001
1 x 10-9
1 billionth
0.21 nm
nano
G. Using the Book
1) It tries to relate physics concepts to everyday life
2) Problems: Word questions (Q), Exercises (E), Challenge (CP)
3) Answers to odd E, CP in back of book; get help if you need it
4) Use the Summary at the end of chapters