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Lecture 1 Physics 103

- Welcome!
- Introduction to the course
- Physics in the World
- Chapter 1

Physics 103 The Cast of Characters

- Lectures (Faculty)
- Matthew Herndon, herndon_at_hep.wisc.edu
- Office hours Wed 330-430, 4219 Cham.
- Tao Han, than_at_hep.wisc.edu
- Laboratory and Discussion (Teaching Assistants)
- 11 TAs 29 sections! (May get bigger!!)
- All sections are full.
- Note Faculty and TAs do not have access to the

registration system. You should go to the

physics department office for registration help.

http//tycho.physics.wisc.edu/courses/phys103/fall

09

Introduction

- Hours per week
- 2 hours
- 2 hours
- 2 hours
- 2 hours
- 4 hours
- 1 hour
- 2 hours

- Basic Course Philosophy
- read about it (text by Serway, Vuille)
- think about it (pre-flight, lectures)
- collaborative learning (discussion)
- experiment with it (labs)
- challenge yourself (homework)
- test your knowledge (disc quizzes)
- close the loop (office hours, tutoring)

We present several opportunities and formats in

which you can learn physics. Please make the best

use of our contact hours, capitalizing on the

format that works best for you. You will do the

learning. Were here to both teach and help you

learn.

Lectures

- Come prepared
- Read material assigned from text
- See Planner
- Do Preflight on the web 5 of your grade
- Preflight 1 for Next Wednesday (Can be done 5

days in advance.) - Lecture itself includes
- Mostly Concepts
- Demos
- Interactive problem solving (questions during

lecture) - Collaborate with your colleagues everywhere

except in exams and quizzes - DO NOT expect to learn by passively sitting and

listening in the lecture - please participate - Lectures are NOT complete - homework,

discussions, quizzes, and labs are needed to

complete learning in this course - Lecture slides are placed on the web after

lecture - Ask questions if you dont understand

Participation you learn by doing!

Discussion and Lab

- Discussion - 15 of your grade
- Work Problems -- collaboratively in groups with

TA - Tuesday, Thursday
- Homework due Friday after discussion
- Quizzes due on Sunday after homework (do it

early!) - Discussion sections are mandatory
- There is no way to makeup a discussion session
- With a valid excuse attendance credit can be

given (documented emergency or academic conflict)

inform us in advance - Lab - 15 of your grade
- Also led by your TA
- Work in groups of 3
- Prelab questions and quizzes or lab notebook

review in lab - Labs are mandatory
- Must do at least 8 of 10 labs to pass this course
- Labs can be made up with a valid excuse
- Make up missed labs during week of lab or midterm

exam weeks - Consult with TA to arrange time

Exams Homework

- Exams
- 3 Midterms 30 of your grade, 1 final 20 of

your grade - Multiple Choice, Bring a formula sheet(1 side

hand written) - Check that you have no conflicts with exam times,

listed in timetable , Oct. 8, Nov. 5, or Dec 3

at 545-700 PM or a final at 1225 AM on

Thursday, Dec 17. - Exams are mandatory, unexcused absence will

result in failure of the course. - Given an excused absence exam grade will be

assigned based on other exam scores - Take the practice exams under time constraint

with your formula sheet - Homework 15 of your grade
- Important for learning, maybe most important!
- Web-based
- Some hints are given
- Try to not use the help button right away
- Try again till you get it right!

A Story

- People have been intrigued by unusual natural

phenomena - E.g., Solar eclipses
- Mythology developed around it
- Great for literature and arts!
- Scientific pursuit centered around the following

method - Design experiments and make observations of

physical phenomena - Propose theories that explain the observations
- Best theories make predictions that can be tested
- Discard theories that dont work.
- Eventually scientists discovered physical laws

that enable prediction of planetary and lunar

motion and thus eclipses - Aristotle, Ptolemy, Copernicus, Tycho Brahe,

Kepler, Galileo, Newton - Laid foundations of modern mechanics
- Reliable navigation was not possible without this

knowledge - Industrial revolution followed
- Positive feed-back gt new physics discoveries,

new discoveries in other fields of interest to

you - microscopes for biology

Motion of the celestial bodies

Apparent motion of stars Rotation about a point

every 24 hours. Moon, sun, and planets were known

to move with respect to the stars.

Motion of the stars over 6 hrs

Daily motion of sun planets over 1 year

Movie by R. Pogge, Ohio State

Retrograde planetary motion

Ptolemys observations of retrograde motion of

Mars Previous theories couldnt explain

this! Continued observation revealed that the

problem was even more complex than first

believed! - Retrograde motion of Mars. - Apparent

motion not always in a perfect circle. - Mars

appears brighter during the retrograde motion.

Epicycles, deferents, and equantsPtolemys

Theory

Earth Centered Epicycle reproduced planetary

retrograde motion, very complex. Needed

epicycles for every planet

The heliocentric universe

Copernicus Competing Theory

- Sun-centered
- Planets orbiting around sun.
- Theory didnt perfectly predict planetary motion.

Only needed elliptical orbits - But the (imperfect) theory was already attractive

in several ways.

Advantage Natural explanation of Retrograde

motion

- Retrograde motion observed as planets pass each

other.

Comparing Ptolemy and Copernicus

- Ptolemys Earth-centered

Copernicus sun-centered

Which is the better theory?

How can we tell if it is correct?

Both explained contemporaneous observations.

- But a rotating and revolving Earth seemed absurd!

Both motions require incredibly large speeds

Speed of rotation 1280 km/hour Orbital Speed

107,000 km/hr 30 km/sec! No observational

evidence of orbital motion Relative positions

of stars did not shift with Earths motion

(parallax) Stars weren't brighter when Earth is

closer (opposition). No observational evidence

of rotation Daily motions are as easily

explained by a fixed earth. The motions do not

require a rotating earth.

Advantage A good theory makes predictions

half-illuminated Venus

Earth

We keep the theories that work And teach them to

you here! What did we get out of this Accurate

navigations charts!

Importance of Physics Awareness

- Large number of Inventions. X-rays, ultrasound,

IPod (last years Nobel prize) - Knowledge of physics is useful in all professions

and in everyday situations. - Do you want to buy stock in a company that

advertises to make perpetual motion machines to

generate free energy? - Is Hydrogen an energy source?
- Will simply going to fuel cell cars eliminate all

harmful gas emissions? - Knowing physics lets you make correct choices

whether in investment or in voting! - But, you must read and learn,
- Challenge yourself, enjoy physics 103 and 104
- If you are a pre-med, you will be able to do the

physics portion of your MCAT exam!

Course Outline

- Mechanics
- kinematics
- energy
- momentum
- rotational motion
- gravity
- Solids Fluids
- Heat
- Waves

Rockets and Satellites Satellite TV, GPS,

Maps Effective water distribution better

understanding of the heart and blood flow Energy

efficient air-conditioning, heat Understanding

of light waves Radio, TV, Cell phones, microwave

ovens

Units

- To communicate the result of a measurement for a

quantity, a unit must be defined - Defining units allows everyone to relate to the

same fundamental amount - Length L meters
- Mass M kilograms
- Time T seconds
- Dimensional Analysis
- Both sides of an equation must have the same

dimensions - Can be used to verify equations, answers

A Concept

- All of these quantities have units
- Distance measured in meters, miles, feet
- Time measured in seconds, hours, years
- Speed meters per second, miles per hour
- Fundamental units
- Derived units
- Speed meters per second (m/s), miles per hour

(mph)

Significant Figures

- There is uncertainty in every measurement, this

uncertainty carries over through the calculations - Use rules for significant figures to approximate

the uncertainty in results of calculations - A significant figure is one that is reliably

known - All non-zero digits are significant
- Zeros are significant when
- between other non-zero digits
- after the decimal point and after another

significant figure - can be clarified by using scientific notation
- Significant figures in a final result equals

significant figures in the least accurate of the

factors being combined - Hint Keep at least one more significant figure

in your calculation than needed until the very

end, then round your final answer

Significant Figure Example

- You are asked to calculate a trajectory for a

space ship to the moon to 1 accuracy. - If your off by more than 1 you might miss the

moon and not have enough fuel to correct course

and land! - 1 is the accuracy we ask for in the homework

questions - Formula distance 1/2 accelerationtime2 x

1/2at2 - Steps. Choose acceleration and calculated time.

Confirm the ship covers the distance and arrives

at the right place! - x 506,000,000m, t 100400sec, a 0.1004 m/s2
- Known to 1 precision 1 part in 100 or 3

decimal places - Case 1 After figuring out t and a we round off

to 1 precision x 1/2at2 1/210000020.100

500,000,000m - Case 2 We keep 4 significant figure to be safe

x 1/2at2 1/210040020.1004

506,024,032m - In case 1 we are 1.2 off. You just killed the

astronauts! - Lesson to get 1 accuracy keep 4 digits and

round at end

Question A

- A very good fastball pitcher can throw the ball

100 mph. What is the ball speed in m/s? - (5 miles is approximately 8 km)
- 4444 m/s
- 44.44 m/s
- .4444 m/s

Order of magnitude estimate A mile is of order

103 meters An hour is of order 103

seconds Therefore, the answer should be of order

102 m/s

Units, Significant Figures, Estimates

- Fundamental Units
- Length L meters
- Mass M kilograms
- Time T seconds
- Dimensional Analysis
- Both sides of an equation must have the same

dimensions - Can be used to verify equations, answers vd/t,

m/s m/s - Significant Figures
- Final significant figures determined by number

with the least significant figures used in the

calculation - Keep as many extra digits as you like along the

way(at least 4 if 1 precision needed) and round

at the end - Order of magnitude estimates also useful to

double check answers