Dr. Tatiana Erukhimova [year]

Overview of Today’s Class Folders Syllabus and Course requirements Tricks to survive Mechanics Review and Coulomb’s Law

Please take the folders Section 807 (recitation starts at 8:00 am R) – red folders Section 808 (recitation starts at 2:20 pm R) – yellow folders Section 809 (recitation starts at 9:10 am F) – green folders Section 523 (recitation starts at 11:10 am R) – blue folders If you forgot your Section number, please check it with me

We’ll use the folders only in class: Please pick them up before each class and return back after the class DO NOT take them home! I’ll return the quizzes in these folders

Syllabus Instructor Dr. Tatiana Erukhimova Homepage Office: Engineering-Physics building, Room 530

Phone: Class times: MWF: 8:00 am to 8:50 am Sections , 523 Location: ENPH 202 Office hours: Monday and Wednesday 1pm – 3pm or by appointment

Textbook: “Don’t Panic: Volume II”, by William H. Bassichis, 5th Edition No lab manual is required Dedicated students like it!

Grade Policy Exams 45% Lab 5% Quizzes 10% Final 40%

You must pass both the lecture (3 midterm exams, final exam, homework) and laboratory (>70%) parts of the course separately in order to pass the course Students not taking or failing lab will receive an Incomplete Grade Policy (cont)

If your grade on the Final Exam is higher than your lowest grade on one of the three exams during the semester, the grade on the Final will replace that one lowest exam grade in computing the course grade (it will only replace one grade in case of two exams having the same lowest grade). The Final Exam grade cannot be used to replace an exam that has been missed without an University excused absence. The missed exam will count as a zero when computing your final grade. Grade Policy (cont)

All Exams are Closed book No numbers! In general the problems will be formula solutions with variables Problems will be similar to those on homework and recitation

Homework You’ll have weekly homework assignments Every week you’ll have hw quiz (for 10 min) with one problem from your assignment. Good news: you are allowed to use YOUR notes (no books or photocopies) Bad news: small partial credit (for hw). You have to show your work, get a correct formula, and, if required, a numerical answer

Check my webpage for hw assignments Example for Week 1 (Week Jan 19): Week Jan 19 (due Jan 26): All Chapter 1 problems and exercises “Due” means that I’ll give you a hw quiz on that day

Homework (Cont) Reading quizzes Please buy clickers (CPSrf responder) You will earn points for reading quizzes based on your participation in class as documented via use of your CPSrf responder. You will not be able to earn points if you fail to bring your personally registered CPSrf responder with you to class each day.

Exam schedule All mid-term exams will be in HELD from 7:00 to 9:30 pm February 17 Exam I March 24 Exam II April 23 Exam III Final May 8

My Advise to You Be proactive!! Get into it and have fun Always read the book before you come to class Be serious about an old rule of thumb: you have to study 2-3 hours a week outside the class per each credit hour Don’t miss classes (lectures, recitations, labs) Solve all problems and exercises after each Chapter in the book Don’t fall into the “I understand the concepts but I can’t do the problems” trap. It means you haven’t done enough of the problems in the chapters. Every year we have lots of students who really think they understand but fail during the exams. Don’t let this happen to you!

Help sessions are every Monday 30 min before the class I also make help sessions before each midterm exam and the final. (and Fridays!) However, these sessions cannot substitute for regular class attendance. They are to give you a good guidance on how to prepare for the test and to succeed in problem solving. Please check my webpage for help sessions schedule

A little bit of Mechanics A couple of very important concepts: ____

does NOT depend on path!

Mechanical energy is conserved!

We can find Gravitational Potential Energy r mm GrU 21 )( 

Consider now a different type of a force…..

Consider a force like gravitation which varies as but 1) billion-billion-billion-billion times stronger; 2) there are two kinds of “matter”: positive and negative; Like kinds repel and unlike kinds attract (unlike gravity where there is only attraction) ++ + __ _

Electrical force All matter is a mixture of positive protons and negative electrons which are attracting and repelling with this great force. How perfect is the balance? -when you stand near someone else you don’t feel any force at all; -if you were standing at arm’s length from someone and each of you had one percent more electrons than protons, the repelling force would be enough to lift a “weight” equal to that of the entire earth! The force that holds atom together, and the chemical forces that holds molecules together, are electrical forces!

Atoms are made with positive protons in the nucleus and with electrons outside This picture is obsolete!

If this electrical force is so terrific, why don’t the protons and electrons just get on top of each other? Laws of quantum mechanics rule it out… What holds the nucleus together? A Helium Atom -There are also nuclear forces – fall off much more rapidly than

An important consequence….. Consider uranium with 92 (!) protons. The balance between the nuclear forces and electrical repulsion is so delicate that the nucleus is almost ready to fly apart. If we “tapped” it slightly……

Matter is effected by forces or interactions (the terms are interchangeable) There are four fundamental forces in the Universe: gravitation (between particles with mass) electromagnetic (between particles with charge) strong nuclear force (between quarks) weak nuclear force (that changes quark types)

The atom contains a nucleus surrounded by a cloud of negatively charged electrons. The nucleus is composed of neutral neutrons and positively charged protons. The opposite charge of the electron and proton binds the atom together with electromagnetic forces.

Atom is mostly empty space! Size of proton or neutron: ~ m Size of an electron cloud: ~ m (1 Angstrom) Proton mass: 1.7x kg Electron mass: 9x kg Magnify a hydrogen atom by the diameter of the electron cloud about 4.5 times longer than a football field

What holds a negatively charged electron together ? (since it has no nuclear force) 1909: Robert Millikan famous oil drop experiment The smallest charge we ever observed is the “elementary charge”: By convention, the electron has negative sign, the proton positive.

Coulomb’s Law Charge Conservation of electric charge Charge is conserved: in any isolated system, the total charge cannot change. If it does change, then the system is not isolated: charge either went somewhere or came in from somewhere is the permittivity of free space

Have a great day! Hw: All Chapter 1 problems and exercises Reading: Chapter 1