mechanics lecture 1, slide 1 welcome to physics 211! classical mechanics

Mechanics Lecture 1, Mechanics Lecture 1, Slide Slide 11

Welcome to Physics 211!Classical Mechanics

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Course Home Page

Course Home Pagehttp://online.physics.uiuc.edu/courses/phys211/summer12/http://online.physics.uiuc.edu/courses/phys211/summer12/

Course Directors

Lecture Doug Davis (dougd@illinois.edu) also (DDavis@eiu.edu) http://ux1.eiu.edu/~addavis/DrD/Welcome.html

Discussion Robert Chamberlain (rchambe2@illinois.edu)

Laboratory Bo Han (bohan2@illinois.edu) Jason Merritt (jmerrtt2@illinois.edu)

Course meetings

Mechanics Lecture 1, Slide 5

The best way to predict the futureThe best way to predict the futureis to invent it!is to invent it!

— — Alan KayAlan KayApple FellowApple Fellow

Course Structure

Spiral Learning 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

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I understand I understand the material.the material.

I just can’t I just can’t dodo the thehomeworkhomework!!

— — James 1:22James 1:22

Additional Resources

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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 GradebookThis 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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Prelectures + Checkpoints + Lectures 100

Labs 150

Hour exams (3 x 100 each) 300

Final Exam 200

Homework (14) + Quizzes (9) 250

Your Grade (see Course Description)

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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Exam Score

ViewerNon-Viewer

Students who… Exam 1 averageViewed pre-lectures 80%Blew through pre-lectures 73%

What we learned in Physics 212

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Mechanics Lecture 1, Slide 19

Physics 211Lecture 1

Today's Concepts:a) Displacement, Velocity, Accelerationb) 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

Time taken

Displacement and Velocity in One Dimension

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Definition:

Speed = |v(t)|

The v(t) vs. t plot is just the slope of the x(t) vs. t plot

Displacement and Velocity in One Dimension

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A) YESB) NO

Are the plots shown at the left correctly related

Displacement and Velocity in One Dimension

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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?

AA BB CC

ACT

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Acceleration

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For the Displacement and Velocity curves shown on the left, which is the correct plot of acceleration vs. time?

AA

BB

Checkpoint 1

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AA

BB

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 A answer

a(t) = slope of v(t).... v(t) decreases then increases (never going negative)... this is confirmed by the displacement graph

Typical B answer

Vote againACT 4

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A ball is thrown straight up in the air.Its position as a function of time is shownin the plot to the right.

Which of the following statements is true as the ball goes up?

A)The acceleration is positive and the ball speeds upB)The acceleration is negative and the ball speeds upC)The acceleration is positive and the ball slows downD)The acceleration is negative and the ball slows down

Acceleration ACT

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Constant Acceleration

constanta(t) = a

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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 feetRamp Demo

Checkpoint 2

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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 B 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

Typical C 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 A answer

Checkpoint 2 Responses

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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 B 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

Typical C 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 A answer

1ft4ft

9ft

3

16ft

Checkpoint 2 Responses

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