Introduction

General Physics (PHY 2130)

•  Syllabus and teaching strategy •  Physics

•  Introduction •  Mathematical review

http://www.physics.wayne.edu/~apetrov/PHY2130/

Chapter 1

Lecturer:

, Room 358 Physics Building, Phone: 313-577-2739, or 313-577-2720 (for messages) e-mail: apetrov@physics.wayne.edu, Web: http://www.physics.wayne.edu/~apetrov/

Office Hours:

MWF 10:40-11:35 AM, at 2009 SCI MW 3:00-4:00 PM, on main campus, Physics Building, Room 358 or .

Grading: 3 in-class exams (100 pts each) 300 pts Quizzes (5 out of 7 quizzes)/attendance 60 pts Final Exam 200 pts Online Homework (WebAssign) 40 pts BONUS: Planetarium visit 3 pts

Syllabus and teaching strategy

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►  PHY 2131 is the laboratory portion of PHY 2130.

  It is a co-requisite

  Laboratory is treated as a separate part of the course ►  Your laboratory Manual will be available on Blackboard

►  For further details: Dr. Scott Payson at 313-577-3280 ►  Lab sections of PHY 2131 begin in week of January 10

LABORATORY

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QUIZ SECTIONS

►  Quiz sections meet once per week and are important.

  Allow you to meet together in small groups.   Practice problems.

►  Quiz instructors will work a few examples.

►  You will be given 7 quizzes (5 best + attendance is reported to me)

►  Five best quizzes plus attendance will be counted toward your final quiz score: Total possible = 60 pts [50 (quizzes) + 10 (attendance)].

►  No individual make-up quizzes will be given

►  Math proficiency test: first quiz section! Make sure you attend.

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EXAMS ►  There will be three regular, so-called “hour” exams (typically 50-55

minutes allowed) given during the term.

►  Each exam consists of Multiple Choice questions (no partial credit).

►  Your lowest score of the three may be replaced by one-half of the final exam score, if doing so improves your grade.

►  There will be NO make-up exams.

►  If you miss an hour exam for any reason, that score of 0 will be your low score.

►  You MUST bring your Wayne State ID to the exam and present it to a proctor when you hand in the exam.

►  No electronic devices (other than a standalone calculator) are allowed in the room during the exam (no iPods, headphones, cell-phones, Blackberries, etc.)

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ONLINE HOMEWORK

►  The WebAssign online testing system (http://webassign.net)

►  40 points of the 600 point total for the course. ►  If you purchase the textbook at the bookstore, it will include a

WebAssign access card valid for two semesters. ( Or purchase it through the internet)

►  Details can be found in the Syllabus. ►  Consult the WebAssign Student Guide for additional information.

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TIPS FOR SURVIVING SUCCEEDING IN INTRODUCTORY

PHYSICS ►  Purchase the text. Make use

of the many helpful aspects of the text.

►  Actually read the text (use a

highlighter, if you prefer). ►  Put in the time. At least 2

hours outside of the class for every hour of lecture.

►  Practice, practice, practice.

►  Strive for understanding. Come to the class.

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ADDITIONAL STUDY HELP

►  Physics Resource Center, in room 172 Physics (the center will open a couple of weeks after the term begins).

►  Your professor and quiz instructor

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NOTE: If you need a certain letter grade in this class to get into/stay in a program, please keep track of your grade throughout the semester to make sure that you are WELL above the required level.

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Introduction

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Why Study Physics?

  Physics is the foundation of every science (astronomy, biology, chemistry).

WSU: diverse set of problems, ranging from understanding the origins of the universe, to probing subatomic interactions, to studying the behavior of magnetic domains in hard drives, to characterizing single molecule diffusion.

 Many pieces of technology and/or medical equipment and procedures are developed with the help of physicists.

  Studying physics will help you develop good thinking skills, problem solving skills, and give you the background needed to differentiate between science and pseudoscience.

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Scientific Notation Is there a shorthand way of writing very large and/or very small numbers?

Prof. Sakamoto’s lab:

Studies of myosin (one of motor proteins)

Size of the object: 10 nm = 0.000000001 m

Prof. Cackett’s lab:

Studies of X-ray binaries (star systems with

one normal star and a black hole)

Size of the object: 130 000 km = 130 000 000 m

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Example: The radius of the sun is 700,000 km.

Write as 7.0×105 km.

Example: The radius of a hydrogen atom is 0.0000000000529 m. This is more easily written as 5.29×10-11 m.

When properly written this number will be between 1.0 and 10.0

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Physics Speak

Be aware that physicists have their own precise definitions of some words that are different from their common English language definitions.

Examples: speed and velocity are no longer synonyms;

mass and weight are no longer synonyms;

acceleration is a change of speed or direction, etc.

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Math

Galileo Wrote: Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these, one is wandering in a dark labyrinth. From Opere Il Saggiatore p. 171 by Galileo Galilei (http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Galileo.html)

Basically, the language spoken by physicists is mathematics.

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x is multiplied by the factor m.

The terms mx and b are added together.

bmxy +=This:

Means this:

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x is multiplied by the factor 1/a or x is divided by the factor a. The terms x/a and c are added together.

caxy +=

Example:

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The general rule is to multiply the quantity by

⎟⎠

⎞⎜⎝

⎛ ±100

1 n

where the (+) is used if the quantity is increasing and (–) is used if the quantity is decreasing by n percent.

Calculating percentages

►  How would you calculate by how much a quantity changed if you are given by how many percent it increased/decreased?

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Example: You put $10,000 in a CD for one year. The APY is 3.05%. How much interest does the bank pay you at the end of the year?

305,10$0305.1000,10$ =×

The bank pays you $305 in interest.

1+ 3.05%100%

!

"#

$

%&

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Example: You have $5,000 invested in stock XYZ. It loses 6.4% of its value today. How much is your investment now worth?

680,4$936.0000,5$ =×

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BA∝

BA 1∝

A is proportional to B. The value of A is directly dependent on the value of B.

A is proportional to 1/B. The value of A is inversely dependent on the value of B.

Proportions

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Example: For items at the grocery store:

weightcost ∝The more you buy, the more you pay. This is just the relationship between cost and weight.

To change from ∝ to = we need to know the proportionality constant.

(weight)pound)per (cost cost ×=

Example

A large ice cube is 30 in on each side. If the length of each side is increased by a factor of two, the surface area

A) increases by a factor of ½. B) increases by a factor of 2. C) increases by a factor of 4. D) increases by a factor of 8.

A large ice cube is 30 in on each side. If the length of each side is increased by a factor of two, the surface area…

Solution:

AnewAold

=6anew

2

6aold2=6 2aold( )

2

6aold2

=4aold

2

aold2

= 4

Given: anew = 2 aold Find: Anew/Aold=?

Notations: let’s call the length of the “old” side as aold and the “new” length as anew.

Recall that each cube has six faces. The area of each face is Aface = a2, so the total surface area is A = 6 a2. Thus,

Note: we did not use the fact that aold=30 in!

Example

A large ice cube is 30 in on each side. If the length of each side is increased by a factor of two, the surface area

A) increases by a factor of ½. B) increases by a factor of 2. C) increases by a factor of 4. D) increases by a factor of 8.

Measurements

► Basis of testing theories in science ► Need to have consistent systems of units for

the measurements ► Uncertainties are inherent ► Need rules for dealing with the uncertainties

Systems of Measurement

► Standardized systems   agreed upon by some authority, usually a

governmental body ► SI -- Systéme International

  agreed to in 1960 by an international committee  main system used in this course   also called mks for the first letters in the units

of the fundamental quantities

Systems of Measurements

► cgs -- Gaussian system   named for the first letters of the units it uses for

fundamental quantities

► US Customary   everyday units (ft, etc.)   often uses weight, in pounds, instead of mass

as a fundamental quantity

Basic Quantities and Their Dimension

► Length [L] ► Mass [M] ► Time [T]

Why do we need standards?

Length

► Units   SI -- meter, m   cgs -- centimeter, cm   US Customary -- foot, ft

► Defined in terms of a meter -- the distance traveled by light in a vacuum during a given time (1/299 792 458 s)

Mass

► Units   SI -- kilogram, kg   cgs -- gram, g   USC -- slug, slug

► Defined in terms of kilogram, based on a specific Pt-Ir cylinder kept at the International Bureau of Standards

Standard Kilogram

Why is it hidden under two glass domes?

Time

► Units   seconds, s in all three systems

► Defined in terms of the oscillation of radiation from a cesium atom

(9 192 631 700 times frequency of light emitted)

Time Measurements

US “Official” Atomic Clock