department of physics and applied physics 95.141, f2009, lecture 1 welcome to physics i !!! prof....

Department of Physics and Applied Physics95.141, F2009, Lecture 1

Welcome to Physics I !!!Prof. Wasserman

LECTURE 1


Outline

• Why Physics?• Course organization• Course grading• Chapter 1

– Significant figures– Units– Estimating


Why Physics?

• Students in this course come from diverse backgrounds and are heading in diverse directions

• Physics provides all with a scientific toolbox– Physics describes the fundamental operation of the world

around us: Engineering, Chemistry, Biology, Astronomy, etc.– Teaches us how to approach complex problems

• Science is inherently progressive– If approached correctly, we can all contribute!

• What you are going to do matters!


Physicists look at the world differently

• This class will attempt to show you how we understand the world around us


Course Organization

• Everything you need to know about the course can be found on the course website: http://faculty.uml.edu/dwasserman/95.141.htm


Course Communication

• Website– http://faculty.uml.edu/dwasserman/95.141.htm

• Physics I Twitter account: @UMLPhysicsIS10

• On Facebook, search for "UML Physics I S2010"


Course Organization

• Physics I meets 4 times a week– Lectures

• 2:30-3:20 MW, OH 150

– Recitation Sections• Varying times, locations• Know your instructor and section number!!!

– Homework review sessions• 6:30-9:30 pm, OH 218• Held every week before HW is due

• Textbook: Giancoli: Physics for Scientists and Engineers, 4th Ed.

• NO LAB THIS WEEK!!• RECITATION SECTIONS THIS WEEK!!


Lecture Organization• Exam Prep. Problem• Review of Previous Lecture• Lecture Main Topic

– Will include clicker questions– Example problems

• Symbolic• Numerical

– Movie clips– Demonstrations

• Summary• LECTURES MOVE FAST!!!


Lectures

• NO COMPUTERS IN LECTURE!!

• NO CELL PHONES!!

• NO TALKING!!


Recitation Section Organization

• Lecture Summary

• Example problems from Book

• Quizzes


Course Grading

Item Points

Standard HW 90

LP HW 20

Quizzes 90

Participation 30

Exam 0 20

Exam 1 100

Exam 2 100

Exam 3 100

Final Exam 200

Total 750

Range Grade

>600 A

560-599 B+/A-

490-559 B

450-489 C+/B-

375-449 C

340-374 D+/C-

265-340 D

<265 F


PRS Clickers

• For detailed info on setting up PRS clickers, go to: http://clickers.wiki.uml.edu/Student+Resources

• You must have your own clicker!!– You cannot borrow a friend’s clicker for class– You may not have more than 1 clicker in class: this is

academic fraud.

• Clickers will be used to determine part of participation grade


Let’s Set-Up Our PRS Clickers

A. Power on your clicker

B. When autoscan begins, press * to stop it

C. Press * to display the Setup Menu

D. Scroll up to display the ID: menu option

E. Press enter (green arrow) to select it

F. Input your Student ID: No Alpha Characters, No Leading Zeros!!!

Press the left arrow to backspace if you make an error

G. If correct, press enter (green arrow) to save your Student ID

H. You may shut off the PRS or Press * and enter (green arrow) to scan for classes


PRS Example

• Enter class letter (or number): then “enter”

• Question: In order to do well in Physics I, you should spend how many hours working on Physics I material for every hour in class (recitation and lecture)?– A) 0-1 HRS– B) 1-2 HRS– C) 2-3 HRS– D) 3+ HRS


Standard Homeworks• Homework assignments online at course website

(http://faculty.uml.edu/dwasserman/95.141.htm)• Most weeks, the written HW is due on Friday (there are 2

weeks when the HW is due Wed.). • There will be a box in the Physics front office where you

can turn your HWs in. HWs will be returned in section within ~1 week.

• HWs must have NAME and SECTION # !!!• Please follow the HW guidelines in the syllabus.• Graded out of 10, total 90/750 of your final grade• Late homeworks not accepted.• Homework review sessions for EVERY homework set.


Lecture Prep Homeworks

• These HWs are designed as review of the previous lecture, and are due before each lecture.

• Usually consist of 2-3 tutorials. You have unlimited attempts to answer.

• Use these as a study guide to keep you up to speed with lectures.

• Count for 20 pts over the course of the semester• DONE ONLINE!!!!• www.masteringphysics.com

– Course “WASSERMANS10”

• Instructions can be found on website for accessing masteringphysics.com


www.masteringphysics.com


Quizzes

• Given by recitation instructor, during recitation.• 90/750 of Final Grade.• No remakes. (for excused absences, recitation

instructor can drop missed quiz).• Normalized to class quiz average (a tough

recitation instructor doesn’t hurt your final grade!)

• Should cover material from previous week’s class/recitation.


EXAMS

• 3 Mid-Term Exams– Each worth 100 pts.– Taken in class.– Each covers lectures from previous exam up to exam

date– No rescheduling– Extra time available for students with disabilities (must

have note from Office of Student Disabilities)

• Final Exam– 200 pts.– Date/Time/Location To Be Announced


EXAM 0

• There will be an Exam 0 in class on Wednesday.• Exam 0 counts for 20 pts.• This is a test of very basic math skills and the

contents of Lecture 1 and Chapter 1.• This is meant to be a tool for you• It will give you a chance to see where your

quantitative skills stand, to see whether you are prepared for this very challenging course.

• The difficulty level of Exam 0 is not indicative of the types of exams I give!!


Physics I Resources

• Need to get help as soon as you feel like you may be falling behind!

• The first person to contact if you are having problems with Physics I is your Recitation Instructor!!

• Recitation Instructors will have office hours each week during which they can meet.

• HW review sessions• UML tutoring center: information on course

website (http://faculty.uml.edu/dwasserman/95.141.htm)


Fun ≠ Easy

• We have worked very hard to make this course fun and interesting!

• But this does not mean the course will be easy.• This stuff matters!!• 1hr in class = 3+ hrs outside of class• You will have to work hard to do well in Physics I.• You will have to be organized to do well in

Physics I.• You will have to come to class to do well in

Physcis I.


Physics I (95.141)

Lecture 0: OnlineBasic Trig., Calc. and other

mathematical concepts.

Lecture 1: Chapter 1


Chapter 1-3: Measurement and Uncertainty

• No measurement is perfectly precise– For any measurement, it is important to give the

uncertainty in the measurement• Either in absolute numbers: 0.1g or 0.2mm, for example• Or in percentage: 10m +/- 2%, or 3.2kg +/- 10%


Chapter 1-3: Measurement and Uncertainty

• If uncertainty is not explicitly mentioned, we assume it to be 1, or a few units in the last digit specified– “The speed of the car was 51.2 mph”

Means…– “The speed of the car was 51.2 mph +/- ~0.1mph”


Significant Figures

• Significant figures: the number of reliably known digits in a number– 45.21 kg 4 significant figures– 0.00495m 3 significant figures

• If you are making a measurement, be careful about how many digits you use!!– i.e. I am 6 ft 4.23457 inches

• Scientific Notation– 4,560,000,000 4.56 x 109


Chapter 1-4: Units

• Units are important!!!• If I am bragging about my weight:

– “I weigh 150!”

Could mean:– “I weigh 150lbs”

Or….– “I weigh 150kgs”

• In Physics we try to use the same set of units:SI: Système Internationale


Chapter 1-4: SI Units

• Length: meters [m]• Time: seconds [s]• Mass: kilogram [kg]• Temperature [K]For dealing with very small or very large numbers, we can

make use of prefixes:

Ggiga109

Mmega106

Kkilo103

mmilli10-3

µmicro10-6

nnano10-9

• 100,000m can also be written as 100 kilometers (km)• 0.0001s could be written as 100 microseconds (µs)


Chapter 1-4: Converting Units

• Sometimes we don’t get problems in the units we like…– Two cars are traveling on the highway, car 1 at

55mph, car 2 travels 200m in 10s. Which is going faster?

– Need to convert between mph and m/s conversion factor

– Car 1

– Car 2

sm81.24

sm20


Chapter 1-6: Estimating

• Why is estimating important?

ccg

sand 6.1ccg

gold 3.19

126.1

3.19

sandbag

goldhead

sandbag

sandbag

goldhead

goldhead

sandbag

goldhead

m

m

V

V


Chapter 1-6: Estimating

• Being able to make order of magnitude estimates is an important skill!!

mh

mx

15

5.13


Chapter 1-6: Estimating (Fermi Problems)

• What is the capacity of this room?• Could try to count every chair• Or could make a quick estimate…


• How many barbers/salons should a town of 300,000 people have?

Chapter 1-6: Estimating (Fermi Problems)


Chapter 1-7: Dimensional Analysis

• Dimensions of a quantity refer to the units that make it up– Speed L/T, i.e. [m/s]– Acceleration L/T2, i.e. [m/s2]

• We can learn a lot simply by looking at the units involved in an expression.

If someone tells you that the speed of a car is given by the following expression:

smkgs

kgmv

mAwithtimemassAv

/][

][][][

][/


Chapter 1-7: Dimensional Analysis

• Later in the semester, we will learn that Force has the units of Newtons [N]

• F=ma• Fg=GM1M2/R2

• What are the Units of G-Universal Gravitational Constant?

department of physics and applied physics 95.141, f2009, lecture 1 welcome to physics i !!! prof....

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