Honors Physics : Lecture 1, Pg 1

Physics I: Lecture 1Physics I: Lecture 1“Mechanics for Physicists and Engineers”“Mechanics for Physicists and Engineers”

Agenda for TodayAgenda for Today

AdviceAdvice

Scope of this courseScope of this course

Measurement and UnitsMeasurement and Units

Fundamental units

Systems of units

Converting between systems of units

Dimensional Analysis

Honors Physics : Lecture 1, Pg 2

Course Info & AdviceCourse Info & Advice

Be prepared and be organized Course has several components:

Lecture (me talking, demos and Active learning).Discussion sections (group problem solving).Labs (group exploration of physical phenomena).

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Lecture OrganizationLecture Organization Three main components:Three main components:

Lecturer discusses class materialThese notes are intentionally incomplete, and should be

complete during lecture or by using text, library, and webpages

» Follows lecture notes very closely

» Not much work, just incentive to attend class, go over examples and problems.

Lecturer does as many demos as possible

» If you see it you gotta believe it !

Students work in groups on conceptual“Active Learning” problems.

» Usually twice per lecture

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Scope of Physics Scope of Physics

Classical MechanicsClassical Mechanics Heat & ThermodynamicsHeat & Thermodynamics Wave BehaviorWave Behavior ElectromagnetismElectromagnetism NuclearNuclear

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How we measure things! All things can be expressed in terms of the

fundamental units:fundamental units:

Length LMass MTime T

For example:Speed has units of L / T (i.e. miles per hour).Force has units of ML / T2 etc... (as you will learn).

UnitsUnits

See text : 2.1

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Units...Units...

Rational Units:Rational Units:mks: L = meters (m), M = kilograms (kg), T = seconds (s)cgs: L = centimeters (cm), M = grams (gm), T = seconds (s)

Irrational Units:Irrational Units:Feet, pounds, slugs...pretty much anything 'non metric'.

We will use mostly rational units, but you may run across some problems using irrational units. You should know how to convert back & forth.

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Length:Length:

DistanceDistance Length (m)Length (m)

To Andromeda Galaxy 2 x 1022

To nearest star 4 x 1016

Earth to Sun 1.5 x 1011

Radius of Earth 6.4 x 106

Football Field 1.0 x 102

Tall person 2 x 100

Thickness of paper 1 x 10-4

Wavelength of blue light 4 x 10-7

Diameter of hydrogen atom 1 x 10-10

Diameter of proton 1 x 10-15

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Time:Time:

IntervalInterval Time (s)Time (s)

Age of Universe 5 x 1017

Age of Grand Canyon 3 x 1014

My age 1.1 x 109

One year 3.2 x 107

One hour 3.6 x 103

Light travel from Earth to Moon 1.3 x 100

One cycle of guitar A string 2 x 10-3

One cycle of FM radio wave 6 x 10-8

Lifetime of neutral pi meson 1 x 10-16

Lifetime of top quark 1 x 10-22

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Mass:Mass:

ObjectObject Mass (kg)Mass (kg)

Milky Way galaxy 2 x 1041

Sun 2 x 1030

Earth 6 x 1024

Boeing 747 2 x 106

Car 1 x 103

Student 7.5 x 101

Dust particle 1 x 10-9

Copper atom 1 x 10-23

Proton 2 x 10-27

Electron 9 x 10-31

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Converting between different systems of unitsConverting between different systems of units

Useful Conversion factors:1m = 3.28 ft1kg = 0.069 slug1 inch = 2.54 cm1 mile = 5280 ft

Example: convert miles per hour to meters per second:

1 mi

hr

mi

hr

ft

mi

m

ft

hr

s

m

s 1 5280

1

3 28

1

36000 447

..

See text : 2.1

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Significant FiguresSignificant Figures

When multiplying or dividing, the answer should have the same number of significant figures as the least accurate of the quantities in the calculation.

When adding or subtracting, the number of digits to the right of the decimal point should equal that of the term in the sum or difference that has the smallest number of digits to the right of the decimal point.

Examples:0.031 2 sig figs3.030 4 sig figs2 1 sig fig.031 * 3.030= .094 2 SIG FIGS 2 * 0.031= .06 1 Sig fig0.03 + 3.030= 3.06 Hundredths 2+ 0.031= 2 Ones

See text : 2.2