LECTURE 1
INTRODUCTION TO PHYSICS
Instructor: Kazumi Tolich
Lecture 1
2
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Reading chapter 1-1 to 1-8
¤ Scientific
method
¤ Units & dimensional analysis
¤ Scientific notation
¤ Vectors and scalars
Scientific method and example
3
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Scientific method is a careful application of experience and reason to answer questions.
Recognize a problem.
1.
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Make a hypothesis.
2.
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As they travel, neutrinos changed their type into two other types so that they cannot be detected.
Predict the consequences of the hypothesis.
3.
§
An experiment measuring neutrinos from other sources should also see the mismatch.
Perform experiments to test predictions.
4.
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The KamLAND experiment measured less electron-type-neutrinos from nuclear reactors than
expected.
Formulate a theory.
5.
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The number of measured electron-type-neutrinos from the sun did not match the expectation from
nuclear fusion model, which produce electron-type-neutrinos.
“Neutrino Oscillation,” changing of neutrino types while neutrinos are traveling, was established.
When findings in nature are expressed mathematically, they are easier to verify or disprove by
experiments.
Quiz: 1
4
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Which of the following statements about science and physics is/are
true? Choose all that apply.
A.
B.
C.
D.
E.
Science requires observations.
Scientific theory can be proven to be incorrect.
Scientific theory can be proven to be correct.
Only hypotheses that predict observable consequences are scientific
hypotheses.
Physics is the study of the general principles of universal phenomena.
Quiz: 1-1 answer
5
A.
B.
C.
D.
E.
True. Science requires observations since a scientific theory is based on verified
observations. Science is observing and understanding the natural world.
True. A scientific theory can be proven to be incorrect if we made any
observation that does not agree with the theory.
False. A scientific theory cannot be proven to be correct since we cannot make
infinite number of observations.
True. Only hypotheses that predict observable consequences are scientific
hypotheses. If a hypothesis does not yield any observable consequence, it is
merely a guess or an idea.
True. Physics is the study of the general principles of universal phenomena.
Physics is the most fundamental science field as all the others depend on it.
Units & dimension
6
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The SI units is a set of standards established by international committee.
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Length in meters (m)
Mass in kilograms (kg)
Time in seconds (s)
Electric current in amperes (A)
Temperature in kelvin (K)
Amount of substance in moles (mol)
Luminosity in candela (cd)
All the other units can be expressed as a combination of the base SI
units.
Importance of having units:
https://en.wikipedia.org/wiki/Mars_Climate_Orbiter
https://www.youtube.com/watch?v=zN9LZ3ojnxY
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Dimension is the physical nature of a quantity.
Countries that do not use the SI units.
Dimensions of some common
physical quantities
Quiz: 2
7
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Which of these equations can represent a physical equality? Choose
all that apply.
A.
B.
C.
D.
3 meters = 3 seconds
1 meter = 1 meter2
3 meters = 1 meter + 2 meter2
4 meters2 = 1 meter2 + 3 meter2
Quiz: 2-1 answer
8
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4 meters2 = 1 meter2 + 3 meter2 [Length2] = [Length2] + [Length2]
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In dimensional analysis, dimensions are treated as algebraic quantities.
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Two quantities can be added or subtracted only if they have the same dimensions.
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The terms on both sides of an equation must have the same dimensions.
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If you have an equation, A = B + C, the dimensions of A, B, and C must be the same.
The dimensions of other choices are not the same on the left-hand and right-hand sides.
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3 meters = 3 seconds [Length] ≠ [Time]
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1 meter = 1 meter2 [Length] ≠ [Length2]
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3 meters = 1 meter + 2 meter2 [Length] ≠ [Length] + [Length2]
Example: 1
9
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If you drive 90 km/h, how fast are
you going in meters per second?
Quiz: 3
10
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Which of the following mathematical expressions are correct? Choose
all that apply.
A.
B.
C.
D.
E.
F.
G.
1000 = 103
0.01 = 10-2
1 = 100
102 x 103 = 105
102 x 103 = 106
106 / 102 = 103
106 / 102 = 104
Quiz: 1-3 answer
11
A.
B.
C.
D.
E.
F.
G.
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1000 = 103 = 10 x 10 x 10
0.01 = 10-2 = 1 / 10 / 10
1 = 100 (by definition)
102 x 103 = 105
102 x 103 = 106
106 / 102 = 103
106 / 102 = 104
In multiplication, the exponents are added.
In division, the exponents are subtracted.
Scientific notation
12
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In scientific nation, a number is written as a
product of a number between 1 (inclusive)
and 10 (exclusive) times a power of 10.
is 3.5 x 103
¤ 0.035 is 3.5 x 10-2
¤ 3500
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Prefixes are also used instead of power of
10.
¤ 3500
m is 3.5 km
Example: 2
13
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A liter (L) is the volume of a
cube that is 10 cm by 10 cm by
10 cm. If you drink 1 L (exact)
of water, how much volume in
cubic centimeters and in cubic
meters would it occupy in your
stomach?
Order of magnitude calculations
14
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In doing rough calculations, or order-of-magnitude calculations, we sometimes round
off a number to the nearest power of 10.
Example: 3
15
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What thickness of rubber tread
is worn off the tire of your
automobile as it travels 1 km
(0.6 mi)?
Vector and scalar quantities
16
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A vector quantity has a magnitude and direction.
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Displacement (m): how far something moved in what direction
Velocity (m/s): how fast something is moving in what direction
Acceleration (m/s2): how fast velocity is changing in what direction
etc.
A scalar quantity has only magnitude.
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Time (s): how long it has been.
Temperature (K): how hot something is.
Mass (kg): how much stuff there is.
etc.