Welcome to Physics 211!
Classical Mechanics
The lecture is very full. Please move toward the center and don’t
leave empty seats. Move from room 151 to room 141 if you can.
Talk to the person sitting next to you and find out their name and the best
thing that happened to them over the summer.
Mechanics Lecture 1,
Course Directors
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Lectures
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Discussion
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Prof. Mats Selen: 9am, 10am (mats@illinois.edu)
Prof. Jose Mestre: 11am (mestre@illinois.edu)
Prof. Greg MacDougall (gmacdoug@illinois.edu)
Lab
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Prof. Alek Aksimentiev (aksiment@illinois.edu)
Course Structure
smartPhysics
There are several parts, all are important:
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Online Prelectures (animated textbook, before lecture)
Online CheckPoints (check knowledge, before lecture)
Lectures – interactive, address issues found by checkpoints.
Online Homework (first deadline next week)
Discussion Sections (start next week)
Go to the right one !
Lab Sections (start THIS week)
05
Get to know the course Home Page
http://courses.physics.illinois.edu/phys211/
Course Home Page
Use the
Syllabus link
http://courses.physics.illinois.edu/phys211/
Syllabus…
Course Home Page
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smartPhysics
http://courses.physics.illinois.edu/phys211/
smartPhysics
Mechanics Lecture 1,
smartPhysics makes it easy to remember
everything related to lecture & homework
Calendar
View
Prelecture
Checkpoint
Homework 1
Homework 2
Course Home Page
Use the
Gradebook
http://courses.physics.illinois.edu/phys211/
Course Gradebook
Go here to register your i>clicker.
Prelecture, Checkpoint,
Lecture, Homework, Lab
and Discussion activity
will be updated weekly.
Prelecture, Checkpoint, &
Homework scores are always up
to date in smartPhysics
Clicker Question
It doesn’t matter which i>clicker version you
have (you can use V1 or V2 in this class)
Do you have your i>clicker with you today?
V1
A) Yes, and I already registered it!
B) Yes, and I’ll register it tonight!
C) No, but PLEASE give me points anyway!
You will not be penalized if you don’t have a clicker today.
Voting for someone else violates U of I academic integrity rules!
V2
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 Possible Points
You may miss up to 3 Prelectures, 3 Checkpoints and 3 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 within
a week.
You can’t miss more than 3 Labs or 3 Discussions, even with an excuse.
More detail (read later)
Prelectures + Checkpoints + Lectures
100
Labs
150
Hour exams (3 x 100 each)
300
Final Exam
200
Homework (14) + Quizzes (9)
250
Prelectures:
50
Preflight's:
25
Lecture participation: 25
You can miss up to 3 of each
For each Homework assignment, a score is assigned out of 100%
For each Quiz, a score is assigned out of 100%
The lowest of the 14 Homework and 9 Quiz scores is dropped.
The remaining scores are added together to give a number out of 2200.
This is scaled to be worth 250 points.
Bonus Points: You can earn up to 1 extra bonus point in every lecture (for a maximum of 25
bonus points for the semester) by getting the right answers to at least 5 of the clicker questions.
At the end of the semester your bonus points are added to your HW/Quiz score (max 250)
Your total score out of 1000 points determines your final grade.
Its just a simple formula – the computer calculates it.
Your grade is determined entirely by the your performance on
the components of the course as described above.
There is no other “extra credit” possible.
A+ (950), A (920), A- (900),
B+ (880), B (860), B- (835),
C+ (810), C (780), C- (750),
D+ (720), D (690), D- (610),
and F (<610).
Q: What are the benefits of smartPhysics?
A: You learn more
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Viewer
Non-Viewer
25
What we learned in Physics 212
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15
10
5
0
43
48
52
57
61
65
70
74
78
83
87
91
96
100
Exam Score
Students who…
Exam 1 average
Viewed pre-lectures
80%
Blew through pre-lectures
73%
How do I get help ?
We can’t answer your
physics questions via email
– it just doesn’t work.
Office hours start after
Labor Day since U of I
buildings are locked on
Sept 2 & 3
Physics 211
Lecture 1
Today's Concepts:
a) Displacement, Velocity, Acceleration
b) 1-D Kinematics with constant acceleration
If you haven't been able to do Prelecture 1 yet, you will not lose
any points. Please do it as soon as you get access.
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Important: We value your Checkpoint work:
How to derive the important equations namely v=vo + at, x=xo +vot+ 0.5at^2, etc
I would really like to discuss the instantaneous velocity and acceleration. I was confused by
the calculus part of the lecture with the integrals and derivatives. I would also really love to
go over the various graphs from distance to velocity to acceleration and compare them and
try to figure out how to draw certain graphs if you are given one to work with. I was
confused with the graphing portion of this lecture. thanks!
I still get negative acceleration mixed up with slowing down sometimes. The rest of the
concepts seem fairly straight forward to me. It did take me a few tries to get the Rolling
down a ramp problem right though.
Excited for PHYS 211! Woot!
The concepts were straight forward, but I thought the application of the concepts in the
problems was more difficult. Discussing problem solving skills in the lecture would be
helpful.
Why we would not be able to use these 'laws of motion' when an object is approaching light
speed, very small or under very strong gravitational attraction.
Made easy concepts harder to understand.
I think that it was well done. Although the animations were a little distracting from the
actual material of the lecture... (although, that might be my poor attention span). However,
the animations of the derived equations (simplifications of specific equations and such)
moved a little quickly and were somewhat hard to follow.
This may not answer the question, but I wasn't sure if you wanted our work or short
answers for the second part of the checkpoint questions.
Prelecture Example
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Prelecture Example
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Displacement and Velocity in One Dimension
Change in displacement
Change in time
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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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Clicker Question
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
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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Clicker Question
Vote again
A
B
Show in smartPhysics
Typical A answer
a(t) is the derivative of the velocity function and the slope of v(t) goes
from negative to positive, so the values of a(t) must go from negative
to positive
Typical B answer
Acceleration is the derivative of the velocity curve. The velocity
decreases, reaches zero, and then increases again. The
acceleration curve must follow the same pattern.
Clicker Question
A ball is thrown straight up in the air.
Its height as a function of time x(t) 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
The concepts of slowing down, speeding up, and
deceleration were a little confusing.
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Your question…
I found the last checkpoint question the most difficult as well as the
concept of acceleration and slowing down vs. speeding up. The second
question in the prelecture confused me as well. Those are the concepts
I'd like to discuss in lecture.
Mechanics Lecture 1,
Constant Acceleration
Show in smartPhysics
42
Checkpoint
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
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Quite a few got this wrong so lets try again…
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
Typical A answer
If the ball moved 1 foot in 1 second then the average velocity is 1 ft/sec.
Therefore when ball travels another 1 second it moved 1 foot.
Typical B answer
Acceleration is 1 foot per second per second, obviously. Therefore, velocity increases
to 2 feet per second, and therefore in the second second moves 2 feet.
Typical C answer
At t=1, the total displacement is 1 foot and at t=2, the total displacement is 4 feet. To
find the displacement between t=1 and t=2, I subtracted … (4 feet - 1 foot)= 3 feet.
Show Demo
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.
3
4ft
1ft
9ft
16ft
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
If the ball moved 1 foot in 1 second then the average velocity is 1 ft/sec.
Therefore when ball travels another 1 second it moved 1 foot.
Typical B answer
Acceleration is 1 foot per second per second, obviously. Therefore, velocity increases
to 2 feet per second, and therefore in the second second moves 2 feet.
Typical C answer
At t=1, the total displacement is 1 foot and at t=2, the total displacement is 4 feet. To
find the displacement between t=1 and t=2, I subtracted … (4 feet - 1 foot)= 3 feet.