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  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   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  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  OscillationsCh. 16  Waves ICh. 17  First Exam  Waves IICh. 18  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 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/m 3  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 PAL a) 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 (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!!