Welcome to Physics 211!
Classical Mechanics
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Mechanics Lecture 1,
Course Home Page
Course Home Page
http://online.physics.uiuc.edu/courses/phys211/summer12/
Course Directors
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Lecture
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Discussion
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Doug Davis (dougd@illinois.edu)
also (DDavis@eiu.edu)
http://ux1.eiu.edu/~addavis/DrD/Welcome.html
Robert Chamberlain (rchambe2@illinois.edu)
Laboratory
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Bo Han (bohan2@illinois.edu)
Jason Merritt (jmerrtt2@illinois.edu)
Course meetings
Mechanics Lecture 1,
The best way to predict the future
is to invent it!
— Alan Kay
Apple Fellow
Course Structure
Spiral Learning
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Online Prelectures (animated textbook, before lecture)
Online CheckPoints (check knowledge, before lecture)
Lectures (very interactive, bring notes)***
Online Homework (first deadline this Thursday)
Discussion Section starts this Thursday
Lab Sections start this Wednesday
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A quick word about Homework
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More about Homework
I understand
the material.
I just can’t do the
homework!
— James 1:22
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Additional Resources
The Mechanical Universe
http://www.learner.org/resources/series42.html
And, . . . Just for Fun
Physics of the 21st Century!
http://www.learner.org/resources/series213.html
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ACT 1
Do you have your i>clicker with you today?
A) Yes, and I already registered it!
B) Yes, and I’ll register it tonight!
C) Yes, but it doesn’t work 
D) No, but PLEASE give me points anyway!
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Course Home Page
Planner
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Course Gradebook
This is official grade book, but is manually updated! All lecture and homework points will be
updated on weekly. Lab and Discussion activity will be updated weekly.
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SmartPhysics HomePage
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SmartPhysics Progress Bars
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Your Grade (see Course Description)
Prelectures + Checkpoints + Lectures
100
Labs
150
Hour exams (3 x 100 each)
300
Final Exam
200
Homework (14) + Quizzes (9)
250
1000 Points
You may miss up to 3 Prelectures, Checkpoints and Lectures and still get all 100 points!
If you miss a Discussion Quiz, Lab, or Hour Exam due to illness, be sure to fill out an
absence form, and bring documentation to 233 Loomis.
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Q: What are the benefits of participating ?
A: You learn more
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Viewer
Non-Viewer
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What we learned in Physics 212
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Exam Score
Students who…
Exam 1 average
Viewed pre-lectures
80%
Blew through pre-lectures
73%
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Mechanics Lecture 1,
Physics 211
Lecture 1
Today's Concepts:
a) Displacement, Velocity, Acceleration
b) 1-D Kinematics with constant acceleration
If you haven't done Prelecture 1 yet, please do so later today
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Prelecture Example
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Prelecture Example
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Displacement and Velocity in One Dimension
Displacement
Time taken
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Displacement and Velocity in One Dimension
The v(t) vs. t plot is just the
slope of the x(t) vs. t plot
Definition:
Speed = |v(t)|
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Displacement and Velocity in One Dimension
Are the plots shown at the left
correctly related
A) YES
B) NO
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ACT
The velocity vs. time plot of some
object is shown to the right.
Which diagram below could be the
Displacement vs. time plot for the
same object?
A
B
C
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Acceleration
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Checkpoint 1
For the Displacement and Velocity curves shown on the
left, which is the correct plot of acceleration vs. time?
A
B
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ACT 4
Vote again
A
B
Typical A answer
For negative t, v(t) is decreasing so its derivative, a(t), must be
negative. For positive t, v(t) is increasing so a(t) must be positive.
Typical B answer
a(t) = slope of v(t).... v(t) decreases then increases (never going
negative)... this is confirmed by the displacement graph
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Acceleration ACT
A ball is thrown straight up in the air.
Its position as a function of time is shown
in the plot to the right.
Which of the following statements is true as the ball goes
up?
A)
B)
C)
D)
The acceleration is positive and the ball speeds up
The acceleration is negative and the ball speeds up
The acceleration is positive and the ball slows down
The acceleration is negative and the ball slows down
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Constant Acceleration
constant
a(t) = a
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Checkpoint 2
At t = 0 a ball, initially at rest, starts to roll down a ramp with
constant acceleration. Suppose it moves 1 foot between
t = 0 sec and t = 1 sec.
How far does it move between t = 1 sec and t = 2 sec?
A) 1 foot B) 2 feet C) 3 feet D) 4 feet E) 6 feet
Ramp Demo
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Checkpoint 2 Responses
Typical A answer
Since the ball moves 1 foot between t = 0 and t = 1 at constant
acceleration, the ball will move the same distance between t = 1 and t = 2.
Typical B answer
Using the given information, the ball moves 1 foot in 1 second, so it must be accelerating at
a rate of 1 foot per second per second. Between time=1 and time=2 seconds, the ball
accelerates to 2 feet per second per second, so it travels 2 feet.
Typical C answer
when the ball moves one foot during t=0 to t=1 the acceleration is 2. The ball will move
4 feet from t=0 to t=2 with velocity 2. therefore from t=1 to t=2 it will move 4-1=3
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Checkpoint 2 Responses
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4ft
1ft
9ft
16ft
Typical A answer
Since the ball moves 1 foot between t = 0 and t = 1 at constant
acceleration, the ball will move the same distance between t = 1 and t = 2.
Typical B answer
Using the given information, the ball moves 1 foot in 1 second, so it must be accelerating at
a rate of 1 foot per second per second. Between time=1 and time=2 seconds, the ball
accelerates to 2 feet per second per second, so it travels 2 feet.
Typical C answer
when the ball moves one foot during t=0 to t=1 the acceleration is 2. The ball will move
4 feet from t=0 to t=2 with velocity 2. therefore from t=1 to t=2 it will move 4-1=3
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