For students enrolled in an introductory physics lab, PHYS 2108 and PHYS 2109 lab classes begin this week (August 20 - 24). You must attend the first week of class or send an email to lab@phys.lsu.edu PRIOR TO CLASS explaining your absence or you will be dropped from the course.

Ray Chastain

Welcome, Physics Majors!

Freshman physics major? (or thinking about becoming one? Are you a physics minor or double major?

If so, You are invited to join us for free pizza!. We will meet:

Friday August 24, 4:30-6:00 pm Nicholson Hall, Room 435

We will give you some important information, like ..

• Who are the important people to know? • How you can do research in physics and astronomy? • Who are The Society of Physics Students?

Rongying Jin (professor)

Department of Physics & Astronomy Office: 229B Nicholson Hall Email: rjin@lsu.edu Tel: (225) 578-0028

Visit my personal website for more information: http://www.phys.lsu.edu/rongying/

You are Science & Engineering Majors.

You are registered for PHYS 2101.

You want to learn PHYS 2101

You want to have good grade !!

??

Fall 2012: PHYS2101 Section 6

Lectures: Concepts will be developed through the lectures, demonstrations and class discussion

Homework: Best way to learn the material: -- Quizzes & Exams mostly based on HW

Reading Assignments: Lecture schedule is provided - read material before lecture!

Class Information is also via WebAssign WebAssign will handle most of your class-related needs: homework, formulae sheets, practice tests

http://webassign.net/student.html

IMPORTANT: Try to log into WebAssign TODAY

✪  Click “I have a class key” then input your class key: lsu 3573 6541.

✪  If you have used WebAssign before, your old password will be in effect

✪  If you have NOT used WebAssign before, you can logon in by using your LSU

PAWS email address without the @lsu.edu, and setup your own password.

✪  If you have a problem in logon, please check:

(1) username (has to be PAWS username);

(2) if you have paid for accessing WebAssign;

(3) if you are in my class roster. Please contact me if you cannot logon.

The first homework assignment is posted.

HW will be due in 1 week ! Start early !!

Class Format - Announcements - Mixture of Power Point and Chalk Board/Overhead - Some theory …. Some problems… - Power Point slides are available on class website & my own website - Please ask questions (and correct me!).

Course details -- see syllabus

Course: •  It is assumed that everyone has credit in PHYS 1100 so the material in Chapters 1-6 (vectors,

1- and 2-D kinematics, Newton’s laws) will only be reviewed in the first two weeks of class. If you tested out of PHYS 1100, you will be assumed to know this material and should review it carefully if you don't remember it well. You will be tested on this material in the third week of class.

•  After the first two weeks the course assumes a more normal pace and will cover most of the section contained in chapters 7 – 20, with the exception of chapter 17, which will be skipped.

•  The core material of the course covers concepts in mechanics, fluids, wave motion, and thermodynamics. The lecture schedule will specifically indicate sections of text that are covered on a given week. Students should read and become familiar with this material before coming to class.

•  Course grades will be determined by quizzes (mostly in weekly base), Homework, four 1-hour mid-term tests, and a final (see following).

Homework: •  Homework assignments will be posted online at: http://webassign.net/student.html

(details announced in class). They are similar to text book HW. •  Except when noted in class, due dates for homework assignments will generally be

midnight on Monday after the assignment. •  Full solutions will be available at webassign after the due date.

Course details -- see syllabus

Quiz: • There will be a quiz (10-15 min.) based primarily on the HW problems due that week.

Tutoring: •  If you do not understand the material or you experience difficulty in working the

problems, seek help from the graduate tutors in Room 102 of Nicholson Hall. This service is free.

•  There will be 2101 Supplemental, which is also free. More information coming soon. •  Make sure you take advantage of the instructor office hours posted. You should feel free

to go to any instructor's office hours if you have class conflicts with your own instructor's office hours; all sections follow the same schedule and use the same homework assignments.

Exams: • There will be four 1-hour mid term exams. • There will be no make-up exams: if you need to miss an exam for a university-scheduled function, make sure you obtain permission from your instructor in advance. If you miss an exam with permission your other scores will be adjusted. • Exams will contain a combination of multiple-choice questions and work problems for which you must show your work. • The scheduled dates for exams are as following:

Exam 1 100 points September 18, 2012 6 – 7 pm Lockett 10 Exam 2 100 points October 16, 2012 6 – 7 pm Lockett 10 Exam 3 100 points November 13, 2012 6 – 7 pm Lockett 10 Final 200 points December 6, 2012 3 – 5 pm TBA

Students having three or more final examinations in a 24 hour period may request permission to take no more than two examinations on the day concerned. These requests must be requested by the student and approved by the instructor before Friday Nov. 9th. • A formula sheet will also be provided and no other material is to be used during the exam. You will need a scientific calculator; graphic calculators are fine, but not necessary. • Old exams (with solutions) are posted here, but notice that the number of exams and material covered in them is different in different years.

Course details -- see syllabus

Grading: •  HW-50 pts. –The two lowest will be dropped. The quizzes and many of the exam questions are taken from the Home Work. •  Quiz - 50 pts. The quiz grade will be computed from the average grade. •  Middle Exams - 100 pts. each: Total 300 pts. •  The final exam will be composed of two parts, an examination of Ch. 18-20 (100 pts) and a separated cumulative part (100 pts). • Your final grade will be based on 600 total points. The demarcations in % of 600 pts are given below • A >88%, B> 77%, C>60%, D>50% • If your percentage grade is within these ranges, you are guaranteed the associated letter grade. At the end of the course the instructors may adjust these cut offs slightly but only downwards.

Course details -- see syllabus

Basic concepts:

1. Measurement of a physical parameter

2. Units, systems of units (example: SI)

3. Basic units in mechanics

4. Changing units

5. Significant figures

SI Base Units – seven 1)  meter (m) distance 2)  kilogram (kg) mass 3)  second (s) time 4)  ampere (A) electric current 5)  kelvin (K) temperature 6)  mole (mol) amount of stuff 7)  candela (cd) intensity of light

See Appendix A: International System of Units See Appendix D: Conversion Factors

Significant figures…

Derived Unit Measures Derivation Formal Def. hertz (Hz) frequency /s s-1

newton (N) force kg·(m/s2) kg·m·s-2

pascal (Pa) pressure N/m2 kg·m-1·s-2

joule (J) energy N·m kg·m2·s-2

or work

prefix Symbol Factor Giga G 109

Mega M 106 Kilo k 103

Centi c 10–2

Milli m 10–3

Micro µ 10–6

Nano n 10–9

“Units” example

Alpha Centauri is the closest “star”. It is 4.3 light-years away. How many kilometers away is the star from earth ?

Write down: What do you know? What are we trying to get to?

4.3 light years = time it takes for light to travel distance

Distance = speed × time What’s the speed (rate)? Speed of light = 3 ×108 m/s

Now do it..

time speed

distance = 4.3 years( ) 3.15 ×107 s1 year

3×108 m

s

1 km

1000 m

= 40 ×1012 km or 40 petameters (Pm)

When we measure physical quantities, the units may be anything that is reasonable as long as they are well defined. It’s usually best to use the international standard units. Density may be defined as the mass of an object divided by its volume. Which of the following units would probably not be acceptable units of density?

a) gallons/liter

b) kilograms/m3

c) pounds/ft3

d) slugs/yd3

e) grams/milliliter

Questions

A certain physical quantity, R, is calculated using the formula: R = 4a2(b – c) where a is a speed (a distance traveled per unit time interval) and b and c are distances. What is the SI unit for R?

a) cm/h

b) cm2/s

c) m2/h

d) m2/s

e) m3/s2

Questions

Given that one inch is equal to 25.4 mm. How many meters equal 11.3 ft?

a) 3.45 m

b) 4.42 m

c) 2.95 m

d) 1.30 m

e) 2.21 m

Questions

Solution:in=25.4mmft=12in=12x2.54mm=304.8mm=0.305m

Which one of the following pairs of units may not be added together, even after the appropriate unit conversions have been made?

a) feet and centimeters

b) seconds and slugs

c) meters and miles

d) grams and kilograms

e) hours and years

Questions

Be sure that numerical answers appear with appropriate SI units. Points will be

deducted for missing, incorrect, or “silly” units.

If the final answer is in fact a dimentionless quantity, please write the numerical result followed by the word

“dimensionless”

Basic Concepts: Displacement:

Average velocity:

Instantaneous velocity:

Average acceleration:

Instantaneous acceleration

(SI Unit: m/s2)

(SI Unit: m/s)

(SI Unit: m)

We are dealing with Kinematics

Example

v1st=ΔxΔt

=+1609 m4.740 s

= +339.5m s

v2nd=ΔxΔt

=−1609 m4.695 s

= −342.7m s

Entire trip: Average speed? Average velocity? 341.1 m/s 0 m/s Δx=0 !

Average Velocity: The World’s Fastest Jet-Engine Car Andy Green in the car ThrustSSC set a world record of 341.1 m/s in 1997. To

establish such a record, the driver makes two runs through the course, one in each direction, to nullify wind effects. From the data, determine the average velocity for each run.

€

vave = v = ΔxΔt

=x − xo

t − to

Can Displacement be larger than Distance? When is it equal?

Special Case: Motion with Constant Acceleration

Motion with Constant Acceleration

The acceleration a is a constant.

The v(t) versus t plot is a straight line with slope = a and intercept = v0.

The x(t) versus t plot is a parabola that intercepts the vertical axis at x = x0.

Example The brakes on your car are capable of creating a constant deceleration of 5.2 m/s2. a) If you are going 137 km/hr and suddenly see a state trooper, what is the minimum time in which you can get your car under the 90 km/hr speed limit? b) How far has your car traveled during the deceleration?

Special Case: free-falling body motion

a

A

B

y

Close to the surface of the Earth all objects move toward the center of the Earth with an acceleration whose magnitude is constant and equal to 9.8 m/s2. We use the symbol g to indicate the acceleration of an object in free fall.

A person standing at the edge of a cliff throws one ball straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed is the one initially thrown

1.  upward. 2.  downward. 3.  neither—they both hit at the

same speed.

Question

Kinematics: Taking Advantage of Symmetry