Welcome to Principles of Physics I (PHYS 2010)

1. UVaCollab site: • Syllabus • Resources (lecture slides, practice exams, etc.) • Gradebook • Feedback MasteringPhysics: web interface for assigned problem sets Welcome to Principles of Physics I (PHYS 2010) Professor Blaine Norum Note on enrollment: If you are waitlisted and not currently registered in a discussion section: Come see me. In most cases I can sign you in. . Note: you MUST attend the first meeting of your discussion section. Failure to do so may result in your being dropped from the roster and replaced by someone waiting

2. Lecture rules No cell phones. No laptops EXCEPT in very last row. Do not interfere with the learning environment Make space for your fellow students If you are sick... don’t come to class.

3. i>Clickers • Questions in lecture will challenge your conceptual understanding, encourage your engagement and provide me with feedback • 1 point for participation, • A second point for correct answer (if scored) • 5% of your course grade: as a fraction of 60% of total clicker points available • You MUST register your i>Clicker for THIS class: go to UVaCollab site. Lectures Format • Electronic slides • Slides will be available after lectures (rarely before) • Frequent demos to build intuition, relate to the real world, and encourage engagement NOTE: I may occasionally miss a class. In this case, your instructor will be another professor with experience in this class.

4. Mastering Physics A web-based homework system • Instantaneous feedback • Multiple attempts at problem solving (guessing discouraged) • Hints, tutorials, and other support • Excellent feedback to instructors • Well designed interface • MCAT study guides (mostly practice MCAT quizzes) • Register using your access code at MasteringPhysics.com • sign up for Walker 4th edition • Use this class code: • Section 1: MPNORUM06885 • Section 2: MPNORUM16384 • use your email/computing ID • Problems: use the online help (“Ask a question”). • There is an introductory assignment (not graded) and also your first assignment (due Friday)available now

6. Is there a curve? Are they hard? Raw averages on the 3 midterms last year: 73%, 77%, 60% On the final: 68% yes. With curve, class average is usually B-/B Exams and Grading • Midterm Exams: • Three midterm tests will be given at the dates and times shown in the syllabus. The tests will be administered during regular class time.  The tests will consist of multiple choice questions. • TEST DATES IN SYLLABUS ARE NOT WRITTEN IN STONE! THEY MAY SHIFT SLIGHTLY! • Final Exam: Final Exam 35% Three Midterm Exams 50% Problem Sets 5% Problem Session Quizzes 5% Quizzes in Lectures (iClickers) 5%

7. Learning in PHYS 2010 Study Techniques • Read the book • Keep a pencil in hand, along with scratch paper (& calculator) • Work example problems. • Work end-of-chapter problems • start with at least one “one dot” problem; a warm-up drill • most odd-numbered questions have answers in the back of the book. • focus on completing the problem, correctly. Small mistake = zero points on the exams • Take advantage of web resources (example: classic problems may crop up on study sites) • Take advantage of office hours My Office Hours Tuesday 3-5, Thursday 3-5, by appointment. Physics Bldg. Rm 136. TA Office Hours Will be posted on Website. You can attend office hours for ANY TA from this course

8. Feedback email Feel free to send comments to me directly. MasteringPhysics comments These are sent directly to me, and also logged for the MasteringPhysics developers Anonymous feedback ...via UVaCollab site. I have often received useful constructive criticism in this format. But remember, since it is anonymous I cannot respond to you individually unless you E-mail me directly

9. Check Syllabus for reading assignment: • (next lecture completes Chapters 2 and 3!) • Do your reading. Have a pencil in your hand. • Do examples. Practice drawing figures. • Register at MasteringPhysics. • look at the introductory assignment (not for credit) • work Assignment #1 (for credit, due Friday at 11:59pm) • Register your iClicker- Go to to UVaCollab, input clicker ID • - bring it to every lecture for extra credit quizzes and questions • NO DISCUSSION SECTIONS THIS WEEK • when we finish, Please exit out the back doors- • So the next class can come in the front.

11. Lecture 1 Introduction to Physics

12. A Quantitative Science • Physics: the study of the fundamental laws of nature • these laws can be expressed as mathematical equations • much complexity can arise from relatively simple laws • this complexity can be analyzed in terms of these simple laws Physics is a quantitative science, based on careful measurements. If you can’t measure it, it ain’t physics!

13. Units of Length, Mass, and Time SI units of length (L), mass (M), time (T) Time: the second One second is the time for radiation from a cesium-133 atom to complete 9,192,631,770 oscillation cycles. Length: the meter Was: one ten-millionth of the distance from the North Pole to the equator Now: the distance traveled by light in a vacuum in 1/299,792,458 of a second Mass: the kilogram One kilogram is the mass of a particular platinum-iridium cylinder kept at the International Bureau of Weights and Standards, Sèvres, France.

14. Units of Length

15. Units of Mass

16. 1021 m 1041 kg Thinking quantitatively allows us to describe objects that are outside our common experience... ... and sometimes find connections we wouldn’t have seen. 10-10 m 10-25 kg 10-14 m 10-27 kg 10-15 m

17. Dimensions and Units • Any valid physical formula must be dimensionally consistent – each term must have the same dimensions From the table: Distance = velocity × time Velocity = acceleration × time Energy = mass × (velocity)2

18. The density of iron is about 8000 kg / m3 . You have an iron brick with dimensions 20 cm x 10 cm x 10 cm. What is the mass of the brick ? Density = [M] / [L3] Volume= [L3] = 0.2 x 0.1 x 0.1 m3 = 2 x 10-3 m3 Mass = [L3] x [M] / [L3] = (8 x 103 kg / m3) (2 x 10-3 m3) = 16 kg

19. Density of big nuclei density = [Mass]/[Volume] = [M] / [L3] Neutron Star: Lead Nucleus: • Neutron Star • 104 m • 2.7x1030 kg • Nucleus of Lead-208 • 5x10-15 m • 2.5x10-25 kg

20. Converting Units Converting feet to meters: 0.3048 m = 1 ft (this is a conversion factor) Or: 1 = 0.3048 m / 1 ft 316 ft × (0.3048 m / 1.0 ft) = 96.3 m Note that the units cancel properly – this is the key to using the conversion factor correctly! There are 1.6 km to 1 mile. If something is traveling with a speed of 15 m/s, what is the speed in miles per hour?

21. Significant Figures • accuracy of measurements is limited • significant figures: the number of digits in a quantity that are known with certainty • number of significant figures after multiplication or division is the number of significant figures in the least-known quantity

22. Significant Figures Example A tortoise travels at 2.51 cm/s for 12.23 s. How far does the tortoise go? (from a calculator: 2.51 x 12.23 =30.6973) Answer: 2.51 cm/s × 12.23 s = 30.7 cm (three significant figures)

23. Units of Length

24. Scientific Notation and Significant Figures • Leading or trailing zeroes can make it hard to determine number of significant figures: 2500, 0.000036 (Each of these has two significant figures) In this case, the trailing zeros are necessary. They are only clearly significant if they are “unnecessary”, as in 2500.0 • Scientific notation writes these as a number between 1 and 10, multiplied by a power of 10: 2500 = 2.5 × 103 0.000036 = 3.6 x 10-5 We can indicate three significant figures as 2.50x103 (now the trailing zeros mean something!)

25. 70 times per minute? call it 100. 60 minutes / hour? call it 50 24 hours/day? call it 20 365 days/year? call it 400 80 years? 130 years? call it 100. 1x102 5x103 1x105 4x107 4x109 Order-of-Magnitude Calculations Why are estimates useful? • as a check for a detailed calculation – if your answer is very different from your estimate, you’ve probably made an error • to estimate numbers where a precise calculation cannot be done Choose useful units, and ignoring the details you don’t need Example: How many times will your heart beat during your life? 4 billion times... if you live to a ripe old age

26. “position” is obviously a vector. Example: when looking at a 2-dimensional map “2 miles South” Scalars and Vectors Note: this implicitly has 2 numbers in it: “0 miles East” Scalar – a numerical value. May be positive or negative. Examples: temperature, speed, height Vector – a quantity with both magnitude and direction. Examples: displacement (e.g., 10 feet north), force, magnetic field “position”corresponds to“displacement”, a vector. length of travel is“distance”, a scaler

27. Position, Distance, and Displacement Before describing motion, you must set up a coordinate system – define an origin and a positive direction. The distance is the total length of travel; if you drive from your house to the grocery store and back, you have covered a distance of 8.6 mi. Your net displacement is zero. 27

28. Position, Distance, and Displacement If you drive from your house to the grocery store and then to your friend’s house, your displacement is -2.1 mi and the distance you have traveled is 10.7 mi. 28

29. 10.7 miles sav = 0.5 hours = 21.4 miles/hr Average Speed The average speed is defined as the distance traveled divided by the time the trip took: Average speed = distance / elapsed time If you drive from your house to the grocery store and then to your friend’s house, your displacement is -2.1 mi and the distance you have traveled is 10.7 mi. The trip takes 30 minutes (with traffic and lights). What is your average speed?

30. Average Velocity Average velocity = displacement / elapsed time If you return to your starting point, your average velocity is zero.

31. Instantaneous Velocity Evaluating the average velocity over a shorter and shorter period of time, one approaches the “instantaneous velocity”. The instantaneous velocity is tangent to the curve.

32. Graphical Interpretation of Average and Instantaneous Velocity

33. x Position v. Time I t a) it speeds up all the time b) it slows down all the time c) it moves at constant velocity d) sometimes it speeds up and sometimes it slows down e) not really sure The graph of position versus time for a car is given below. What can you say about the velocity of the car over time?

34. x Position v. Time I The car moves at a constant velocity because the x vs. t plot shows astraight line.The slope of a straight line isconstant. Remember that theslopeof x vs. t is the velocity! t a) it speeds up all the time b) it slows down all the time c) it moves at constant velocity d) sometimes it speeds up and sometimes it slows down e) not really sure The graph of position versus time for a car is given below. What can you say about the velocity of the car over time?

35. x t Position v. Time II The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? a) it speeds up all the time b) it slows down all the time c) it moves at constant velocity d) sometimes it speeds up and sometimes it slows down e) not really sure

36. x The car slows down all the time because the slope of the x vs. t graph is diminishing as time goes on. Remember that the slope of x vs. t is the velocity! At large t, the value of the position x does not change, indicating that the car must be at rest. t Position v. Time II The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? a) it speeds up all the time b) it slows down all the time c) it moves at constant velocity d) sometimes it speeds up and sometimes it slows down e) not really sure

37. Check Syllabus for reading assignment: • (next lecture completes Chapters 2 and 3!) • Do your reading. • Register at MasteringPhysics. • work Assignment #1 (for credit, due Friday at 11:59pm) • Register your iClicker- Go to to UVaCollab, input clicker ID • - bring it to every lecture for extra credit quizzes and questions • NO DISCUSSION SECTIONS THIS WEEK Please exit out the back doors- So the next class can come in the front.