Physics 101: Lecture 1, Pg 1 Welcome to Physics 101! Lecture 01: Introduction to Forces “[in high school] all we did was make trebuchets, pasta towers, and toothpick boats. It was fun, but we didn’t learn much.” “I am very excited about taking Physics 101!” “lectures seem fun with all the experiments” “Nervous” “Anxious” “Apprehensive” “…will be a change from my biology based classes.” “I have to take it to graduate… crap”

Physics 101: Lecture 1, Pg 2 Meet the Lecturer l Charles Gammie l Office Hours Monday Loomis l Research è Astrophysics – black holes! l P101 is one of my favorite courses!

Physics 101: Lecture 1, Pg 3 Course Format (upward) Spiral Learning l Lecture Preflights 25 l Lecture Participationclickers 25 l Homework100 l Lab 150 l Discussion 100 è quizzes; drop lowest 1 l Hour Exams (3 x 100)300 l Final Exam

Physics 101: Lecture 1, Pg 4 Grading Scale l A+ l A l A- l B+ l B l B- l C+ l C l C- l D+ l D l D- l <610 F “Let’s get a good grade…”

Physics 101: Lecture 1, Pg 5 Reading & Lecture Preflight l Need to complete PreLecture for Preflight l Answer preflights 25/1000 points è Due 6:00 am day of lecture. è 1 points for honest attempt at preflight (lose points for nonsense – and I read these!). è No EX, 28 Lectures can miss three and still get all 25 points. l Everyone gets 1 point for today!

Physics 101: Lecture 1, Pg 6 P101 Lectures l Participation is key! è Come to lecture prepared! è 1 point for each lecture using iclicker »No EX, 28 Lectures can miss three and still get all 25 points. »Available at bookstore---register using link on web page. l Not everything you need for exams! è Concepts, Connections, Motivation è Comprehensive Text è Calculations Homework + Discussion è Hands-OnLab l Taking Notes è Lecture notes available for lecture. è Some key pieces for you to fill in. “I’m looking forward to a fun … semester”

Physics 101: Lecture 1, Pg 7 P101 Homework l All web based, immediate feedback l 100% if done before 6:00 am deadline l 90% credit on unfinished parts until following Tuesday l 0% after that l Always keep 5 significant figures! l First two are due Tues Feb 2 !

Physics 101: Lecture 01, Pg 8 P101 Labs l Director: Professor Robert Clegg l First is Today! l No “dropped” labs….. Don’t miss one! “I am excited to see what kind of labs we will be doing.”

Physics 101: Lecture 1, Pg 9 Discussion Sections l Director: Professor Yoshi Oono l Start: yesterday! l Quiz during last 20 minutes of section l 10 minutes late  l First section: math review, dimensional analysis.

Physics 101: Lecture 1, Pg 10 Physics Philosophy l Physics is DIFFERENT l Describe large number of “complicated” observations with a few simple ideas l Exams don’t have same problems, but do have same IDEAS “I do better in classes that require memorization.”

Physics 101: Lecture 1, Pg 11 Newton’s Laws of Motion 1. If the sum of all external forces on an object is zero, then its speed and direction will not change. Inertia 2. If a nonzero net force is applied to an object its motion will change F= ma 3. In an interaction between two objects, the forces that each exerts on the other are equal in magnitude and opposite in direction.

Physics 101: Lecture 1, Pg 12 Forces in P101 l Non-Contact ---- Gravity (|F| = G m M/r 2 ) è G = 6.7x m 3 / (kg s 2 ) è Earth: Mass = 6x10 24 kg, radius = 6.4 x10 6 m. l Contact (fundamentally E+M) è Normal: Perpendicular to surface è Friction: Parallel to surface è Anything touching the object »Rope: Tension »Spring F = -kx

Physics 101: Lecture 1, Pg 13 Example Weight of Object l Calculate the gravitational force on a 3 kg book held 1 meter above the surface of the earth. |F| = G M m / r 2 = (6.7x m 3 / (kg s 2 )) (6x10 24 kg) (3 kg)/ (6.4x ) 2 m 2 = 29.4 kg m/s 2

Physics 101: Lecture 1, Pg 14 Gravitational ACT l If the book is raised 10 meters above the surface of the earth, the gravitational force on the book will A) 100 times stronger B) 10 times stronger C) Nearly the same D) 10 times weaker E) 100 times weaker F = G M m / r 2 = (6.7x10-11 m 3 / (kg s 2 )) (6x10 24 kg) (3 kg)/ (6.4x ) 2 m 2 = 29.4 kg m/s 2 Near surface of earth r = 6.4x10 6 m |F| = m (G M /r 2 ) = m (9.8 m/s 2 )

Physics 101: Lecture 1, Pg 15 Contact Forces: Friction l Magnitude of frictional force (parallel to surfaces) is proportional to the normal force.  f kinetic =  k N  k coefficient of Kinetic friction  f static <=  s N  s coefficient of Static friction l Be Careful!  Static friction <=, can be any value up to  s N è Direction always opposes motion

Physics 101: Lecture 1, Pg 16 Free Body Diagrams l Choose Object (book) l Label coordinate axis l Identify All Forces è Hand (to right) è Gravity (down) è Normal (table, up) è Friction (table, left) Physics y x

Physics 101: Lecture 1, Pg 17Summary l Newton’s Laws of Motion è Inertia è F=ma è Pairs l Forces: è Non-Contact: Gravity è Contact: Friction and Normal l Free Body Diagrams è Each direction is independent l Friction opposes motion, parallel to surface  Kinetic f =  k N  Static f <=  s N

Physics 101: Lecture 1, Pg 18 To Do l Discussions started already, Labs start today. l Do lecture preflight before 6:00 am Monday! l Have a GREAT WEEKEND! 50