Welcome to Physics 215!

Welcome to Physics 215! (General Physics I – Honors & Majors) *Please pick up a syllabus*

SU PHY215 General Physics I Fall 2011 Course staff: • Lecturer: Prof. Britton Plourde (bplourde@physics.syr.edu) • Workshop instructor: -- Shiliyang “Bryce” Xu (sxu01@physics.syr.edu)

Physics Laboratory Course (PHY 221) • Faculty: Prof. Ken Foster • Lab section taught by teaching assistant • Separate course • Register separately • Independently graded • Lab manuals will be distributed during lab meetings

Course Information(http://physics.syr.edu/courses/PHY215.11Fall/index.html) • Books - Physics for Scientists and Engineers, Vols. 1 & 3, 2nd edition, R.D. Knight - Accompanying Student Workbook • Announcements/reminders of exams and homework assignments • Course outline, objectives • Course calendar • Lecture slide shells, homework solutions, exam solutions

Objectives Objectives for this course: • Develop good understanding of a few important concepts • Reason qualitatively and quantitatively • Learn to apply to unfamiliar situations • Get a flavor of more advanced topics outside of the standard Mechanics curriculum

Course Outline • Weeks 1-4: Motion (Kinematics) • Weeks 5-6: Newton’s Laws (Dynamics) • Weeks 7-9: Energy, momentum • Weeks 10-11: Extended objects, rotations • Week 12: Gravity • Week 13: Thanksgiving break • Weeks 14-15: Fluid mechanics, oscillations, waves, sound

Lectures • Finish reading assignment beforehand! • During lecture, we will... • Discuss key concepts • Observe demonstrations • Work through sample problems • Consider conceptual questions • Shells of lecture slides available evening before

Workshops • Graduate teaching assistant • During workshops you will work in groups of 2 or 3 students • Wednesdays – workbook problems, practice exams • Fridays -- problem solving activities • TA is there to help you but not to lecture • Hands-on learning experience! • Attendance is required

Physics 215 Fall 2011 Agenda for this week: Tuesday: Intro, velocity Wednesday: Motion diagrams (Workbook) Thursday: Kinematics and graphs Friday: Problem Solving Activity on Motion with graphs

Exams • 3 Exams during semester • Each exam will focus on material from previous ~3-4 weeks, but may include earlier material as well • 80-minutes each, during lecture period • Closed book, but can bring one 8.5” x 11” sheet of handwritten notes (no photocopies) • Practice exam questions in Wed. workshop before each exam • Solutions posted online after each exam is graded • Exam 1 -- Sept. 22 • Final exam • Cumulative • 2 hours -- Dec. 15, 3:00-5:00PM

Homework • Weekly homework • Typically due in Wednesday workshop, except as noted • Assigned at least one week before due date • Combination of end-of-chapter problems, conceptual questions, exam-style problems (print out from course website) • Reminders of assignments on course website • Solutions to select problems posted online after due date • No late homework will be accepted • HW1: • Ch.1 (Knight): 36, 40, 52, 56; Ch.2 (Knight): 26, 34, 40 • due Wednesday Sept 7th in recitation • TA will grade each HW set with a score from 0 to 5

Grades • Exams 1-3 (drop lowest) 40% • Final exam 25% • Homework (drop lowest 2) 25% • Workshop participation 10% • (can miss 2 meetings w/o penalty) The grades are normalized such that the average course grade is a B- or better, depending on the performance of the class as a whole.

Kinematics--describing motion 1D

Position and Displacement • Neglect shape of object and represent by point moving in space (1D) • Position may be specified by giving distance to origin – x coordinate • Choice of origin arbitrary! – many choices to describe same physical situation. • Hence x-coordinate not unique

Displacement = change in position x2 x1 Q O P origin • Displacement(PQ) = x2 - x1 = Dx • Displacement does NOT depend on origin!

Displacement • Displacement is ‘distance plus direction’ • Displacement Dx is a vector quantity – change in position (vector) of object • In one dimension, this amounts to a sign • Displacement towards increasing x – positive • Displacement towards decreasing x – negative

Velocity • Definition: Average velocity in some time interval Dt is given by vav = (x2 - x1)/(t2 - t1) = Dx/Dt • Displacement Dx can be positive or negative – so can velocity – it is a vector, too • Average speed is not a vector, just (distance traveled)/Dt

Discussion • Average velocity is that quantity which when multiplied by a time interval yields the net displacement • For example, driving from Syracuse  Ithaca

Instantaneous velocity • But there is another type of velocity which is useful – instantaneous velocity • Measures how fast my position (displacement) is changing at some instant of time • Example -- nothing more than the reading on my car’s speedometer and my direction

Describing motion • Average velocity (for a time interval): • vaverage = • Instantaneous velocity (at an instant in time) • vinstant = v = • Instantaneous speed • |v|

Instantaneous velocity • Velocity at a single instant of time • Tells how fast the position (vector) is changing at some instant in time • Note while Dx andDt approach zero, their ratio is finite! • Subject of calculus was invented precisely to describe this limit – derivativeof x with respect to t

Velocity from graph x Vav= Dx/Dt As Dt gets small, Q approaches P and v  dx/dt = slope of tangent at P Q P Dx Dt instantaneous velocity t

Interpretation • Slope of x(t) curve reveals vinst (= v) • Steep slope = large velocity • Upwards slope from left to right = positive velocity • Average velocity = instantaneous velocity only for motions where velocity is constant x t

When does vav = vinst ? • When x(t) curve is a straight line • Tangent to curve is same at all points in time • We say that such a motion is a constant velocity motion • we’ll see that this occurs when no forces act x t

Summary of terms • Positions: xinitial, xfinal • Displacements: Dx = xfinal - xinitial • Instants of time: tinitial, tfinal • Time intervals: Dt = tfinal - tinitial • Average velocity: vav = Dx/Dt • Instantaneous velocity: v = dx/dt • Instantaneous speed: |v| = |dx/dt|

Reading assignment • Kinematics and graphs • Chapter 1 and 2.1 - 2.3 in textbook

Welcome to Physics 215!