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

1. Physics I: Lecture 1“Mechanics for Physicists and Engineers”Agenda for Today Advice Scope of this course Measurement and Units Fundamental units Systems of units Converting between systems of units Dimensional Analysis

2. Course 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).

3. Lecture Organization • Three main components: • Lecturer discusses class material • These 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

4. Scope of Physics • Classical Mechanics • Heat & Thermodynamics • Wave Behavior • Electromagnetism • Nuclear

5. See text : 2.1 Units • How we measure things! • All things can be expressed in terms of the fundamental units: • Length L • Mass M • Time T • For example: • Speed has units of L / T (i.e. miles per hour). • Force has units of ML/ T2etc... (as you will learn).

6. 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: • 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.

7. Length: DistanceLength (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

8. Time: IntervalTime (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

9. Mass: ObjectMass (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

10. See text : 2.1 Converting between different systems of units • Useful Conversion factors: • 1m = 3.28 ft • 1kg = 0.069 slug • 1 inch = 2.54 cm • 1 mile = 5280 ft • Example: convert miles per hour to meters per second:

11. See text : 2.2 Significant 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 figs • 3.030 4 sig figs • 2 1 sig fig • .031 * 3.030= .094 2 SIG FIGS 2 * 0.031= .06 1 Sig fig • 0.03 + 3.030= 3.06 Hundredths 2+ 0.031= 2 Ones