Dr. Tyler Nordgren Physics 231: General Physics I

Dr. Tyler Nordgren Physics 231: General Physics I Today 1 st -Day-of-Class logistics 1 st -chapter-of-the –book big picture / stage setting vector refresher Motion is neither created nor destroyed, but transferred via interactions.

Intro to Course o This Semester: Modern Mechanics o Mechanics = Kinematics (motion) & Dynamics (interaction) o Fundamental Principle of Mechanics o “Modern” o Simulations o Level o Math o Algebra & basic Trig o Calculus o Slow start o Physics o No Previous required o Deeper than High School Alternative  Phys o The Difference o Time to decide. o Special Needs o Roll Call

Syllabus Office Hours: Monday 1:00pm-3:00pm, Wednesday 2:00pm-4:00pm Course Components  Reading  Text  If you don’t have it  Assignments o Reading Exercises o WebAssign  User name: first_last, Password: Appleton  Free Trial  Demonstration  First Assignment  (Weekly) Homework  Exploring Physics  First One  Lab – bring laptop if you have one  Quizes  Exams  Schedule

Misc. o Web-site – it’s all there o Supplies  Pencil  Paper / notebook  Calculator o Working Together o Cheating Today’s Reading 1.1Kinds of Matter 1.2Detecting Interactions 1.3Newton’s First Law of Motion 1.4Describing the 3D World: Vectors 1.5SI Units

Q1.2.a: Moving objects left the traces shown at left. The dots were laid down at equal time intervals. Which objects did NOT interact with another object somewhere? 1. A 2. B 3. C 4. D 5. A and D 6. A and B 7. A, B, and D

Q1.2.b Which of the following can NOT be true for an object moving in a straight line at a constant speed? 1.Nothing is interacting with the object (it is in interstellar space, far from all other objects). 2. The object is experiencing a net interaction. 3. The object is experiencing multiple interactions, and these interactions add up to zero. 4. The object has no net interaction with the rest of the world.

Newton’s First Law – “An object moves in a straight line and at a constant speed except to the extent that it interacts with other objects.”

Forces – How are you here? Forces between atoms. Forces between atoms and Earth. Forces between Earth and Sun. Forces between Sun and Galaxy. Forces between Galaxy and ?

Practice with Vectors

A A’s Position: units (relative to the origin) Component Representation:

Practice with Vectors A A’s Position: units B B’s Position: units Component Representation:

Practice with Vectors A A’s Position: units B B’s Position: units Graphical / Arrow Representation:

Practice with Vectors A B Subtraction: May not be obvious. Imagine walking from Origin to A then to B. A friend at the Origin meets you at B. In the end you are both the same distance from the Origin. So: O  A  B = O  B r A + r B  A = r B OR r B  A = r B - r A

Practice with Vectors A B Subtraction:

Practice with Vectors A B Subtraction:

Q1.5.b What is − ? 1) 19 2) ) 4) 5)

Practice with Vectors A B Magnitude:

Practice with Vectors A B Magnitude: Pythagorean's Theorem:

Practice with Vectors A B Magnitude: Pythagorean's Theorem:

Q1.5.d What is the magnitude of the vector in some arbitrary units?

Practice with Vectors A B direction:

Practice with Vectors A B direction:

Practice with Vectors A B direction:

a. b. c. d. e. Q1.5.e What is the unit vector in the direction of the vector in some arbitrary units?

For next time. Buy the book. if you won’t have it by Friday. Sign in to WebAssign, Do RE1 tonight. For Friday do RE2. Labs begin THIS week: AHON 1101 Starting Friday, all lectures in AHON 116.