Thomson Template

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Physics 1710Section 4 InstructorMatteson
Session 2 Chapter 1 Measurement
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Physics 1710Chapter 1 Measurement
Joe College Seat 53 1/14/02
Session 1
Foolscap Quiz

• Name_______ Seat ____
• Date _______ Session 2
• Response Card ________ (Tell me if you do not
  have one)
• E-mail address ________at_____.___ (if you did not
  receive message from Matteson_at_unt.edu)

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Physics 1710Chapter 1 Measurement

• Fact
• The earth has a circumference of approximately 40
  million meters (4. X 107 m). How fast must one
  move on average to travel around the world in 80
  days?

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Physics 1710Chapter 1 Measurement

• 1' Lecture
• First 3 Fundamental Units
• Time, measured in seconds 1/86 400 of m.s. day
• Length, measured in meters c (1/299 792 458
  sec)
• Mass, measured in kilograms specimen
• Prefixes scale units to convenient size.
• Density is mass per unit volume. kg/m3
• Avogadros number is the number of atoms in a
  mole of an element, NAvogadro 6.022x1023
• Significant figures tell the tale.
• Scientific notation saves ink.

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• QA
• Q Is this class mainly for engineers? I ask this
  because I am pre-med. Does this course apply to
  my field?
• A(s) No, it is for scientists as well.
• Yes, it does apply to your field.
• You will learn facts about how things move,
  e.g. consider muscles, joints, blood, air.
• You will grow an understanding of dynamics,
  e.g. energy, momentum and trauma.
• You will develop analytical and qualitative
  skills, e.g. think about diagnosis and drug
  dosing.
• This course is for all scientists and engineers.

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• Laboratory Introduction
• Physics 1730
• Dr. John Prince

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• Mattesons Dicta Numbers 1 2
• 1. Physics is that branch of science concerned
  with the interaction of matter-energy in
  space-time.
• 2. The physical universe consists of only matter
  and energy and the vacuum.
• Late breaking news what about dark matter and
  dark energy? They are 95 of universe and we
  dont yet know what they are.

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Measurement is the quantitative comparison of a
physical parameter to a standard unit.
Existential Physics Activity Measure the
width of the top of your desk in hands.
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• Why did we observe a variety of values in our
  measurement?

• Measurement is the quantitative comparison of a
  physical parameter to a standard unit.
• ? A hand is not a standard unit.
• Our measurement is subject to error.
• Our measurement is coarse.

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Measurement is the quantitative comparison of a
physical parameter to a standard unit. Therefore
we need standards. Accuracy is the difference of
a measurement from the (unknown) true value. All
measurement contain experimental error. Precision
is the fineness of the division of the scale
used to compare to the standard unit. Precision
limits our knowledge.
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• 80/20Precision is the fineness of a measurement.
• 80/20Accuracy is the correspondence of a
  measurement to an (unknown) true value.

Measurement
Less precise
Standard
Less accurate
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Significant figures
What numbers one writes down reveals ones
knowledge (and ignorance) of the actual true (but
unknown) value. Example2. 2.0 2.01
2.0085 2.00852 represent the values of a
measurement at various levels of precision.
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Rules for Computing with Significant Figures

• When multiplying (or dividing) numbers, round
  result to same number of significant figures as
  the factor with least number of significant
  figures.
• When adding (or subtracting), first round to same
  decimal place as contribution with the least
  precision, then compute.

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Rules for Rounding

• If remainder is less than 5, truncate, i.e.
  round down.
• Example 3.1415927 3.14
• If remainder is larger than 5, round up.
• Example 3.1415927 3.1416
• If remainder is exactly 5, round up or down to
  leave last digit even.
• Example 31½ 31.5000 32.

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• Scientific Notation
• Number Mantissa x 10 Exponent _._____ E__
• Big Numbers 1.234567 x 10 3 1234.567
• Small Numbers 1.234567 x 10 2 0.01234567

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• Know Your Calculator

Activity Enter 1.234567 EXP or EE
03 Display should read 1.234567 03 or
1.234567E03 Enter 1.234567 EXP 03
/- or ? or (-) Display should read
1.234567-03 or 1.234567E-03
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• Fundamental Units

• Système International de Metrique (SI) Metric
  System
• First introduced in France in 1799(on
  Napoleons coup)

La
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Time Standard second s

• (1/60)(1/60)(1/24) 1/86,400 mean solar day
• 9,192,631,770 (exactly) times the period of
  vibration of a Cesium-133 atomic clock.
• Time Demonstration

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Length standard meter m

• Meter defined in 1799, by Napoleons Republic.
• 1/107 quadrant of Earth C? 4.00x 107 m
• Distance light travels in 1/299,792,458 sec
• Meter Demonstration

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Derived Units of area and volume

• Area 10 m x 10 m 100 m 2 1 are
• 100 ares 1 hectare 1x104 m2 1 US acre
  0.4046 ha
• Volume m x m x m m 3 1000 liter 1000 l
• e.g. 1000 cm 3 1 liter 1 US gallon
  3.7854118 liters 3.8 l

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• Mass Standard kilogram kg

• kilo 1000, 1 kg 1000 gram
• 1 kg is the mass of approximately 1/1000 m3
  (1 liter) of water
• Mass is a fundamental property of all matter.
• Each atom has a mass of 1.66 x 10-27 kg times
  its atomic mass number

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• Mass Standard kilogram kg
• 1 kg weighs on earth about 2.2 pounds.

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• Amedo Avogadro
• (1776-1856)
• Italian Physicist
• Proposed Avogadros Law (1811)

22.8 liters 1 mole of gas
6.022 x1023 molecules or atoms
12 g C 1 mole
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NA 6.0221367(28) x 10 23 atoms/mole Atomic
mass unit u u 1.660 540 2(10) x 10
27kg ( 1 2/3 yoctogram) NA ? u 1.00 x 10 3
kg 1.00 gram NA is the number of atoms in one
gram molecular weight of an element.
Avogadros Number
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Practice How much does a 5 US Gal can of water
weigh?
Density of water 1.0 kg/l M ? V (1.0 kg/l
)(5 gal x 3.8 l/gal) 19. kg W 2.2 lbs/kg x
19. kg 42. lbs
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• Summary

• Fundamental Dimensions and Units
• Time, measured in seconds
• Length, measured in meters
• Mass, measured in kilograms.
• Prefixes scale units to convenient size. k
  1000, M 1 000 000 c 1/100, m 1/1000, µ
  1/1 000 000
• Density is mass per unit volume. ? m/V kg/m3
  
• Avogadros number is the number of atoms in a
  mole of an element. 6.022 x1023 atom/mole

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• 1' Essay
• What was that about?
• An Aha!
• A Question
• Turn in Foolscap.
• Come to
• Recitation in Room 102
• 100 p.m. Today!