Welcome Physics 202 Professor Lee Carkner Lecture 1

Questions to Consider  Am I in the right place?  Physics 202: Basic Physics  Do I have the right stuff?  Halliday, Resnick, and Walker, 6 th Edition  Lab manual  Calculator  WebAssign Card

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   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 )  Institution is “augustana”  Password is your augustana student ID number  You can change this  After login, click on the current assignment and complete it  WARNING: Can only submit it once  I will post a tutorial later today

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  More specifically: what are the underlying rules that govern how things work?  We will deal mostly with classical physics:  i.e. How did things work before 1900?

Why Take Physics?  You may need to know how things work  You can learn how to:  Use reason and logic  Solve problems  Use mathematics  It is useful to understand how we know how things work

Course Outline  Fluids Ch. 15  OscillationsCh. 16  Waves ICh. 17  Waves IICh. 18  First Exam  1 st Law of ThermodynamicsCh. 19  Kinetic Theory of GasesCh. 20  2 nd Law of ThermodynamicsCh. 21  Second Exam  Electromagnetic WavesCh. 34  ImagesCh. 35  InterferenceCh. 36  DiffractionCh. 37  Final Exam

Fluids  A fluid is a substance that can flow  A liquid or a gas  A fluid has no internal structure  Since a fluid can flow, any individual piece of the fluid can be hard to keep track of  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  Liquids are much less compressible than gases  The SI unit of density is kg/m 3  Air ~1.21 kg/m 3  Water ~1000 kg/m 3  Rock ~3000 kg/m 3  Metal ~8000 kg/m 3

Pressure  Pressure is defined as the force per unit area P=  F/  A  The SI unit of pressure is the pascal (Pa), a newton per square meter  An important practical unit of pressure is the atmosphere, the pressure of the Earth’s atmosphere at sea level 1 atm = 1.01 X 10 5 Pa = 14.7 psi

Fluids and Gravity  We will normally deal with fluids in a gravitational field  Fluids in the absence of gravity will form a sphere  Fluids on a planet will exert a pressure which increases with depth  For a fluid that exerts a pressure due to gravity: 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: P=p 0 +  gh  Pressure usually depends only on the height of the fluid column  The  gh part of the equation is called the gauge pressure  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  Since the pressure of a fluid depends only on its height, this set-up can be used to measure pressure  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  If you close off one end of the tube and keep it in vacuum, the air pressure on the open end will cause the fluid to rise  This is called a barometer  Measures atmospheric pressure

Barometers

Pascal’s Principle  Pressure applied to an enclosed fluid is transmitted to every portion of the fluid and the container  Pascal’s principle is the basis for the hydraulic lever  Consider our U-shaped tube:  If you apply a pressure at one end, the same pressure is felt at the other end  But what if the other end of the tube is thicker?

A Hydraulic Jack

Hydraulic Jack  Since the pressures are the same and the areas are different, the force on the other end is larger (from P=F/A)  But work must be conserved:  W=Fd, so if the force is greater at the other end the displacement must be less  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 (today’s lecture reading) for tomorrow  No lab this week  Check WebAssign for Wednesday’s homework  Due before 10 am Wednesday!!