What is a Physicist?
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Visualize a physicist
“Paint” a picture
Names in Physics?
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Newton
Einstein
Pascal
Faraday
Fermi
Shockley
Aristotle
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… only a selection!
Archimedes
Hawking
Tesla
Hubble
Feynman
Henry
Hertz
What is the Goal of Physics?
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To use a small number of
basic concepts, equations
and assumptions to describe
the physical world.
Physics is the study of the
laws of nature, because
physics is everywhere!
Areas within Physics
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Mechanics
•
motion, forces
Thermodynamics
•
heat & temperature
Vibrations and wave phenomena
Optics
•
light, mirrors
Electromagnetism
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electricity & magnetism
Relativity
•
particle motion
Quantum mechanics
•
behavior of submicroscopic particles
Scientific Method – basis of
scientific investigation
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Make observations and collect data that lead to a
question
Formulate and objectively test hypotheses by
experiments
Interpret results and revise hypothesis if necessary
State conclusions in a form that can be evaluated by
others – develop a theory!
Measurement in Physics
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Systems of units
• (SI) Metric MKS
• Meter (M)
• Kilogram (K)
• Second (S)
• English FPS
• Foot (F)
• Pound (P)
• Second (S)
Common Conversion Values
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1 meter = 39.37”
1 inch = 2.54 cm = 0.254 meters
1 mile = 1609 meters
1 kilogram = 2.2 lbs
1 oz = 28 grams
60 mph = 28 meters/sec
km/h > m/s = 1609/3600 = x 0.45
Common Prefixes
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Pico (p)
Nano (n)
Micro ()
Milli (m)
Centi (c)
Kilo (k)
Mega (M)
Giga (G)
Tera (T)
10-12
10-9
10-6
10-3
10-2
103
106
109
1012
<
<
<
<
<
<
Significant Figures
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The numbers 1 to 9 are always significant
digits.
Zero ("0") is a significant digit if it comes to
the right of a number between 1 and 9.
• 50.3
• 3.0025
• 0.892
• 0.0008
• 57.00
• 2.0000
>3 sig figs
>5 sig figs
>3 sig figs
>1 sig fig
>4 sig figs
>5 sig figs
Significant Figures: +-x/
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When you add or subtract numbers, always
check which of the numbers is the least precise
(least numbers after the decimal). Use that many
decimals in your final answer.
 97.3 + 5.85 = 103.15 rounded to 103.2
When you multiply or divide numbers, check
which number has the fewest sig digs. Round off
your answer so it has that many sig digs.
• 123 x 5.35 = 658.05 rounded to 658
Scientific Notation
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A number in (pure) scientific notation is of the
form
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a * 10n , where
• 1 < a < 10,
• n = a number
• Ex. 3.4 * 107, 9.1 * 10-4
Scientific Notation on Your Calculator
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Most calculators now have a key on them for doing
scientific notation. Look for one of the following...
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EXP (most Casio calculators)
EE (most TI calculators, and you might have to use the 2nd
function key to use it)
Sometimes expressed in convenient terms!
Minimum Measurement
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Whatever the scale (units) on a measuring device, the
error you should record is one half of the smallest
division.
Often this is stated as the "possible error" in the
measurement.
Example 4: If you measure the length of a pencil using a
regular ruler (they usually have 1 mm divisions) and find
that it is 102 mm long, you should write down…
• Length = 102 ± 0.5 mm
Steps in Problem Solving
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List the given data (Given)
List what has to be found (Find)
Draw and label a diagram, if possible
Which principles & equations are relevant to the problem –
how are they used?
Simplify the equations and solve the unknowns in algebraic
form
Check for unit consistency and convert if needed
Insert numerical values and calculate the result, observing
significant figures and calculator requirements – use
parentheses if in doubt!
Check your answer – does it make sense?
Guesstimation!
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Basic skill for finding “ballpark” answer
Example
• Roughly, how many cans of soda are
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consumed by Stauntonians – population
25,000 – in a year?
Assumptions:
•½
of population drink soda 4 times a week
• Calculations
• 25,000 x ½ x 4 x 52 = 2.6 million cans!
Summarize Critical Thinking
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Given:
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Find:
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Tools:
• what do I know?
• what are the unknowns?
• What concepts (therefore equations) can be used
to solve the problem?
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Solve:
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Check:
• Use the tools to solve the problem
• Does the answer make sense?
Graph Relationships
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Linear: y = mx + b
Graph Relationships
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Quadratic: y = ax2
Graph Relationships
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Inverse: y=1/x