Welcome

Physics 202Professor Lee

CarknerLecture 1

Questions to Consider

Am I in the right place? Physics 202: Basic Physics

Do I have the right stuff? Halliday, Resnick, and Walker, 6th Edition Lab manual Calculator WebAssign Card

Must register with Webassign with card before Dec 4!

Things to Know Professor

Dr. Lee Carkner Office Hours

MWF 11:15-12:15 (after class) Science 208

Help session: TBA

Lab section See me after class to change No lab this week

How Does the Class Work?

Read the book material before class Do the exercises through WebAssign

Come to class Do the PAL discussion questions

Come to discussion and do the discussion exercises

Lab once a week Two tests and final

Web Page

http://helios.augustana.edu/~lc/ph202

Outline gives homework and readings

Lectures posted online before class Download and bring to class, fill in

blanks

Grading

Exams (2): 30% (15% each) Final: 20% Lab: 20% Discussion: 10% Pre-class Homework: 10% In-class PAL: 10%

PAL What is PAL?

Physics Active Learning Each class you will get a PAL worksheet Contains questions about the material

and feedback opportunities Worth 10% of your grade

Need to do readings and come to class Can drop (or skip) three PAL’s

“Physics is your PAL!”

Guidelines for Work Handed In

Written answers must be in complete sentences

Numbers must have units Answers must reasonable

If not reasonable, explain why All work must be neat and easily

readable

WebAssign Homework will be entered and graded online

At webassign.com Click on student login Username is your first and last name together

(as in your augustana email) Institution is “augustana” Password is your augustana student ID number

Or same as from PH201 After login, click on the current assignment and

complete it WARNING: Can only submit it twice

What is Physics?

Phys"ics (?), n. The science of nature, or of natural objects; that branch of science which treats of the laws and properties of matter, and the forces acting upon it; especially, that department of natural science which treats of the causes (as gravitation, heat, light, magnetism, electricity, etc.) that modify the general properties of bodies; natural philosophy.

--Webster’s Dictionary 1913

What is Physics?

Physics is a way of figuring out how things work

We will deal mostly with classical physics:

Why Take Physics?

You may need to know how things work

You can learn how to:

It is useful to understand how we know how things work

Course Outline Fluids Ch. 15 Oscillations Ch. 16 Waves I Ch. 17 First Exam Waves II Ch. 18 1st Law of Thermodynamics Ch. 19 Kinetic Theory of Gases Ch. 20 2nd Law of Thermodynamics Ch. 21 Second Exam Electromagnetic Waves Ch. 34 Images Ch. 35 Interference Ch. 36 Diffraction Ch. 37 Final Exam

Fluids

A fluid is a substance that can flow

A fluid has no internal structure

Mass and force are often not useful The important quantities of a fluid

are density and pressure

Density

The density () of a fluid is the mass per unit volume for an arbitrary volume element

Density can vary with temperature or pressure

The SI unit of density is kg/m3

Air ~ Water ~ Rock ~ Metal ~

Pressure

Pressure is defined as the force per unit area

P=F/A

An important practical unit of pressure is the atmosphere, the pressure of the Earth’s atmosphere at sea level

Fluids and Gravity

We will normally deal with fluids in a gravitational field

Fluids on a planet will exert a pressure which increases with depth

p=gh Where h is the height of the fluid in question,

and g is the acceleration of gravity

Gauge Pressure If the fluid has additional material pressing

down on top of it (e.g. the atmosphere above a column of water) then the equation should read:

Pressure usually depends only on the height

of the fluid column

A tire gauge that shows a pressure of “0” is really measuring a pressure of one atmosphere

Measuring Pressure If you have a U-shaped tube with some liquid in it and apply a

pressure to one end, the height of the fluid in the other arm will increase

This describes an open tube manometer Since air is pressing down on the open end, the manometer

actually measures gauge pressure above air pressure or overpressure

This is called a barometer Measures atmospheric pressure

Barometers

Today’s PALa) Suppose you take a 1 cm in diameter glass tube and

seal the top and keep it in vacuum (so there is no air pressure acting on the tube). How high must a column of water be in the tube for it to produce 1 atmosphere of pressure at the bottom?

b) If you doubled the diameter of the tube but kept the water at the same height, how would the pressure change?

c) If you brought the tube to Mars, would the pressure increase, decrease or stay the same? Explain.

Please answer the questions at the bottom

Pascal’s Principle Pressure applied to an enclosed fluid is

transmitted to every portion of the fluid and the container

Consider our U-shaped tube:

But what if the other end of the tube is thicker?

A Hydraulic Jack

Hydraulic Jack

But work must be conserved:

A person can lift a car with a hydraulic jack, but ratcheting the jack 3 feet may only move the car an inch

Next Time

Discussion tomorrow Read 15.1-15.6 (today’s lecture reading) for

tomorrow If you are in the first discussion section,

please see me

No lab this week Check WebAssign for Wednesday’s

homework Due before 10 am Wednesday!!