Galileo Principle:

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http//astro.temple.edu/elenab/
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What Is Physics?
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Galileo Principle

• -recognize that a scientific problem exists
• -state a hypothesis, an educated guess about the
  problem
• -predict the consequences of the hypothesis
• -perform experiments to see if the predictions
  occur
• -formulate the simplest general rule that
  organizes the hypothesis, predictions and
  experimental results into a theory.

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Sir Isaac Newton under an apple tree
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(No Transcript)
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Models of Atom
JJ Thomson PLUM PUDDING!
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Models of Atom
Ernest Rutherford PLANETARY MODEL!
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What is light?
Huygens No way! Its a wave!
Sir Isaac PARTICLE!
Albert Einstein and Max Planck Guys, guys! You
BOTH are right!
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• Is the following hypothesis scientific?
• The alignment of planets in the sky determines
  the best time for making decisions
• Intelligent life exists on other planets in the
  universe
• Life forms evolve from simple to more complex
  forms

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• Which if these are scientific hypothesis?
• Atoms are the smallest particles of matter that
  exist.
• Space is permeated with an essence that is
  undetectable.
• Albert Einstein was the greatest physicist of the
  twentieth century.

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Measurements
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UNITS of SI system
For now we are interested in the base quantities
of length, time, and mass. In the SI system
(formerly known as the MKS system), their units
are Quantity unit
symbol length meter
m time
second s mass
kilogram kg
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1 meter (abbreviated m) was originally chosen to
be one ten-millionth of the distance from the
Earths equator to either pole (1790). 1 second
(s) was defined as 1/86400 of a mean solar day.
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Power of Ten Notation
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Some Lengths or Distances
Proton radius
10-15 m Atom
10-10 m Football
field length
102 m Earth diameter
107 m Earth to Sun
1011 m Farthest
galaxy visible
1026 m
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Some Masses
Electron 10-30
kg Proton
10-27 kg Mosquito
10-5 kg Person
102 kg Earth
6x1024 kg Sun
2x1030 kg Galaxy
1041 kg
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Some Typical Time Intervals
Lifetime of very unstable particle
10-23 s Lifetime of muon
10-6 s One day

10 5s One year
3x10 7
s Length of recorded history
10 11 s Life on Earth
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17 s Age of Universe
10 18 s
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Order of Magnitude
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1. What are the criteria for accepting a theory as a
   physics law?
2. What role does the prestige of the scientist play
   in accepting a theory as a physical law?
3. What is the height of typical person, in
   centimeters? The length of typical newborn baby?
   The typical height of a bedroom ceiling?
4. What is the typical mass of 6-foot tall male, in
   kilograms? Of a 5-foot 6-inch tall female in
   kilograms?

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SUMMARY
For a new idea to be accepted, it must (1) agree
with the existing data (2) make predictions that
can be tested, and (3) have a scientific
basis. The measurement system used in science is
the metric, SI system, based on meter, kilogram,
and second. The sizes of objects studied in
physics range from entire Universe down to
neutrons and protons.
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Describing MotionKinematics in one dimension
Kinematics is a part of mechanics, which is the
description of how objects move.
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Translational motion
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Reference Frame
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Speed
Speed is a measure of how fast object moves,
measured by a unit of distance divided by a unit
of time.
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Instantaneous Speed
Average speed doesnt indicate the different
speeds that may have taken place during shorter
time intervals.
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Average Speed
average speed total distance traveled/ time
elapsed Total distance traveled average speed
X time