Physics 218

Alexei Safonov

Lecture 1: Introduction

Today Lecture• Structure of the class • Organizational issues

– Instructors, textbooks, meeting times• Course requirements and grading

• Practical details– Exams– Homework and quizzes– Reading assignments– Recitations

Physics 218: Basics• Content:

– Introduction to Classical Mechanics– Concepts, Problem Solving, and Labs– Requires high school level calculus

• Structure:– Lecture (2 per week) – MPHY203 (here)– Recitation (1 per week)- MPHY335 or 336– Lab (1 per week) – MPHY 234 or 233

Instructors• Lectures (MPHY 203, MW 4:10pm):

– Alexei Safonov (me)– Email: safonov@tamu.edu

• Put PHYS218 first in the Subject line!!!– MIST M319, 979-845-1479

• The “tower” portion of the Physics Building– Office hours: M 2:30-4:00 PM

• Tentatively, likely to change• Recitation and labs:

– TA’s will provide contact info at your first meeting– First meeting already this week

eCampus• Your main starting point, everything else is

linked to it

Lecture notes• Link for lecture notes:

– http://people.physics.tamu.edu/safonov/218/– I will also add a link to it in ecampus

• Another exceptionally (!) useful site:– http://physics218.physics.tamu.edu/

Syllabus• On my web-site, will also appear in howdy

and ecampus

Co-Requisites• MATH 151

– It is a GOOD idea to take it before this class– If you do well in MATH 151, you will survive

here too, but you are in somewhat disadvantaged position as many of your classmates took calculus in high school

• Gauge yourself:– A lot of math in the first week (quizzes,

reviews, checkpoints) – a great opportunity to assess your situation• If you can relatively easily get 80+% right, you ok• If not, consider coming back next semester

PHYS-218• An “inverted” course:

– Heavily interactive with the material reviewed under different angles• Pre-lectures, lectures following up on your pre-lecture

performance, interactive recitations with content-reach problems

– Research shows substantially increased learning outcomes compared to standard courses• Third time it is offered at TAMU

• A common course with common practices:– Grade determined by your performance compared to

everyone else in PHYS-218 (well over 1,000 people)– Unified grading policy across the whole course

How It’s Meant to Work• You: go over online pre-lectures, do quizzes (part of pre-

lectures), read material of the chapter BEFORE the lecture– You should have pretty good grasp of the material when you come

here at conceptual level and have already done at least some problems

• Me: in lecture I focus on fixing typical misunderstandings and misconceptions and help you learn how to think “right”– Still heavy focus (50-60%) on conceptual understanding, but about

40% practical examples (incl. problems) demonstrating concepts• You: Do homework problems until you can do almost any

problem in the book– Most of you will struggle in the beginning, but if you keep pushing

you will start “getting it” and there is no other way really• Recitations: focus on solving challenging problems, help

with remaining challenges

Materials• Get them right now or the bookstore may

run out of them:– Buy and Register your clicker ASAP!– Register for Modified Mastering Physics ASAP!

• MP packet comes with new textbooks or loose-leaf book options, also available separately in the bookstore, also can pay online (via eCampus)

– Make sure it says “Modified”!

– Register for FlipItPhysics and WebAssign• Do both tonight!!!• Note you can use their free trial offers (see syllabus)

– Textbook (see syllabus)

Common PHYS-218 Web-page

Grading• Grading will be based on the following scales:

• I will curve all scores AFTER the final, but will give you feedback along the way– If your final score is higher than the lowest of the

midterms, that midterm be replaced by an average score on that midterm and the final

FlipItPhysics• Pre-lectures that you work on before the

lecture (for credit and required)– Pass check-points and send feedback

Modified Mastering Physics• Online homework management system

– Weekly assignments (for credit), somewhat elaborate grading system with (harsh!) penalties for late submission

– Only access it via eCampus, do not use direct links for registration! – you do not need a “course ID”

More on Lectures• A follow up on the pre-lectures

– Focus on specific problems, typical mistakes and feedback from your work on pre-lectures

– I assume you already know all basics and more and focus on challenges, misconceptions etc.

• Clicker quizzes – These are for credit, designed to check on your progress and

facilitate your learning• Many “simpler” questions, but some will be pretty challenging

• A lot of focus on conceptual understanding plus problems to illustrate the application of concepts– Focus on “illustrative” problems in lecture, few hard problems

• Lectures give you the tools and teach you how to connect things, the rest is you applying this knowledge as you train yourself in solving problems using homework

Recitations• Common implementation for all sections of this

course• You typically have to do the homework before

the recitation• At recitations, you will be working in groups of 3-

4 learning to work out challenging problems– Multiple concepts in a single problem– Recitation instructor will facilitate your work, but will not be

solving the problem for you– Each student will be turning in their own report, which will be

graded• Additional short quizzes very possible

Labs• Lab policies are uniform and set by the Department

– WebAssign is the online system used by the lab portion of the course

• Register today: http://webassign.net/tamu/login.html– It will take you to TAMU SSO page to identify you, then will automatically place you in

the right class

What to Expect: PHYS-218• Be prepared that this is one of very hard

and time consuming classes– Need typically 12 hours of hard work a week

besides classes• Inter-relation and intensity of the material

makes it harder:– You miss one thing, but it will come and bite

you several times as the same concepts repeat throughout the course

• If you can’t afford that much time, take this class next semester

Independent Perspective• From koofers.com

How To Do Well in PHYS-218• Strategy:

– Maximize scores in all “service” categories• Labs, recitations, HW, clicker quizzes

– Do your best on the exams• Exams are the “make it or break it” part of the course• Will “break it” if you don’t do well in “service” categories

• Final grade math’s “rules of thumb”:– Low scores on HW will likely cost you a whole letter grade

• Most people have 90% and more on homework– Low scores on labs or recitations will likely cost you a whole

letter grade• Most people will have 80-90% for both

– 60% of those who frequently do not participate in clicker quizzes and pre-lecture quizzes will lose a whole letter grade

• If you are in very high C range otherwise, you may still get a C; if you are in the lower 60% of the C range, you will almost definitely get a D

How To Do Well in PHYS-218• You won’t do well on exams unless you train

yourself in solving HW problems– Do problems yourself: if someone explains you the

solution and you “understood” it, that’s not good enough

– If you are stuck, ask for help with a similar problem; if you had to get help with a HW problem, solve 5 more similar ones from the book yourself

– Really helps to go beyond HW assignments and do more problems from the book

– You will struggle withy many of the problems first, but that’s the only way to get through. If you keep pushing, you will notice that there will be a break though point where things will start coming to you easier

Clicker• Model called “i>clicker 2”

– The original i>clicker will be okay as well, but your other classes may require i>clicker2

• Get them now before the bookstore ran out of them!– There seem to be some options to get

a discount when you purchase your text book (see my web-page)

• Today use as a practice only, next time we will use it for real

Registering Your clicker• 1.Go to http://www.iclicker.com/support/registeryourclicker/ • 2.Enter your first and last names as they appear on your TAMU ID.• 3.For "Student ID" enter your TAMU UIN.• 4. For "Remote ID" enter the code that appears on the back of your

i>clicker2 (also on the LCD screen upon powering on your i>clicker2)

Clickers Setup• Turn on your clicker (press the power

button)• Set the frequency:

– Press and hold the power button– Two letters will be flashing– If it’s not “BD”, press “B” and then “D”

• If everything works, you should see “Welcome” and “Ready”

Clicker Question 1• Do you have your i>clicker with you today?

A) Yes

B) No

C) Maybe

D) I like pudding

We use the “BD” frequency in this class

Prepare for Monday• Read material of Chapter 1 ASAP• Do pre-lectures and check-points in

FlipItPhysics – check due dates (typically Monday 8am)– Provide feedback

• Lecture quizzes– You will need your clicker up and running!

• Don’t forget the recitation and lab meetings this week– For many of you it is tomorrow and your

attendance is mandatory (will be checked)

MATH & SUCH

Converting Units• Problem: express length of a football field in feet:

– 1 football field = 100 yards– 1 yard = 3 feet

• Solution:– 1 football field = 1 football field– 1 football field = 1 football field x (1) x (1)

• Can always multiply by a unity; nothing should change – 1 football field = 1 football field x (100 yards/1 football field) = 100 yards

• Got to yards above, which is already an improvement– 1 football filed = 100 yards x (3 feet/yard) = 300 feet

• Got rid of yards and expressed in feet!– Both are units of length!

• Another problem:– Express speed v= 50 km/hour in m/sec

Problem Solving Overview

• There are good general problem solving TRICKS

– Units checking– Special case checking– Etc.

• There are good METHODS of problem solving that prepare you for the exams

We’ll use both to solve problems in lecture

Problem Solving -1What’s the first thing you should do

when you’re given a a problem?• Draw a diagram!!!

–Usually good for some partial credit • List givens and wants as variables

–Also a good bet for partial creditThen use reasonable equations and

solve with variables

Problem Solving -2• The speed of your car isn’t measured in

seconds, its measured in meters/second (or miles/hour etc.)

• Paying attention to the units will help you catch LOTS of mistakes on exams, quizzes and homework!!– If we ask what the mass of your car is,

make sure your answer is in kg (or lbs etc.)

Every time you finish a problem ALWAYS check the units of your answer!!

Problem Solving - 3Check Reasonableness:• Can you find another way to do the

same problem that gives the same answer?

• Trivial choices of values for variables give expected numerical answers? Example: Zero, or infinity

Moving toward an Example Problem

• Next we’ll do an example problem like one of the homework problems in the text book

• Solve this problem using the right method– Draw a diagram– Convert the numbers to variables– Solve to get a formula– Plug in the numbers at the end– Check

Example ProblemYou want to measure the height of a building. You stand 2m away from a 3m pole and see that it’s “in line” with the top of the building. You measure 16 m from the pole to the building.

What is the height of the building?

16 m

Vectors

Vectors: –Why we care about them–Addition & Subtraction–Unit Vectors–Multiplication

Why do we care about Vectors?• As you may have noticed, the world is not one-

dimensional• Three dimensions: X, Y and Z. Example:

1. Up from us2. Straight in front of us3. To the side from us

– All at 90 degrees from each other. Three dimensional axis.

• Need a way of saying how much in each direction

For this we use VECTORS

Vector and Scalar• Vectors have a magnitude AND a

direction–10 miles in the south direction

• Scalars are just a number–Mass of your car–Earth radius

Where am I?

A single vector in arbitrary direction can be thought of as

two vectors in nice simple directions (like X and Y). This can make things much easier

• Let’s say I’m here • You’re here (origin)• I call you on the cell phone. • How do I tell you how to

get to me?• 2 equivalent ways:

• Travel 11.2 km at an angle of 26.5 degrees

• Travel 10 km East then 5 km North

Vector Addition

• To specify where I am, often doing the two vector version is easier

Represent Graphically:• Lay down first vector • Lay down second vector

– Put the tail at the head of the first vector

• The “Sum” is where I am

Re-write my location• Describe my location

in terms of the sum of two vectors

• Careful when using the sin and cos

Θ|R|||RΘ|R|||RR R R

Y

X

YX

sincos

Rx

Ry

R

Specifying a Vector• Two equivalent ways:

– Components Vx and Vy– Magnitude V and angle q

• Switch back and forth– Magnitude of V |V| = (vx

2 + vy2)½

• Pythagorean Theorem– tanq = vy /vx

• Either method is fine, pick one that is easiest for you, but be able to use both

Things Due This Week• Homework (via masteringphysics.com)

– Chapter 1: Math and stuff – due Sunday (3 days from now!)• FlipItPhysics pre-lectures & check-points:

– Math and related topics – due Friday (2 days from now)– Chapter 1 – due Sunday

•Monday lecture:– Finish up Math & stuff, move to Chapter 2

•Before Monday start working on:– Prepare for recitation on Chapter 1– Homework problems for Ch. 2– Pre-lectures for Chapter 2 due Wednesday 8AM!

• Wednesday lecture: – Chapter 2 quizzes

• Lab (WebAssign!):Prepare for the lab, complete all read pre-lab parts before the lab!