Required Materials

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Required Materials

• Textbook and Web Homework Access Kit
• Physics for Scientists and Engineers ( Knight)
• Mastering Physics Student Access Kit
• (Bundled with New Textbooks)
• Class ID PHYS2211SPR07

www.physics.gatech.edu/
academics/Classes/Spring2007/2211/ABCDE/index.html
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Course Information
http/www.physics.gatech.edu
Academics
Class Information
Spring 2007 Classes
PHYS 2211

• This is the official 2211 Web Page
• You are responsible for knowing the policies
• discussed on this page.

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Action Items for This Week

• Read Chapter 1 of textbook
• HW (assigned)
• Labs start next week
• Repeaters Lab Exemption
• PHYS2802 Problem Solving
  Workshop

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MasteringPhysics
Symbolic answers When you are asked to supply a
formula or symbolic expression MP will check to
see if all the proper symbols are present. If
you are missing something or have something that
is not part of the solution it will tell you. If
you have all the proper symbols MP will randomly
assign a value to each variable and then compute
a value for the correct answer and your
expression. If the two numerical results are the
same it gives you credit. More attempts are
wasted misspelling variables than anything else.
Drag the cursor over a variable and it will tell
you how it is to be entered.
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Learn to use the display math tab before you
submit a complex expression to be sure it is what
you intend.
Numerical answers Do your calculations with
three significant digits and you will stay out of
trouble. MP counts an answer correct if it is
with 2 of what it thinks is the correct
answer. Warning MP will tell you you are
close and may have a rounding error when you are
within 5 of the correct answer. Dont believe
it and keep burning attempts, you may be doing
something totally wrong. MP has a calculator
feature that will allow you to input a symbolic
expression rather than a number but why would you
do it? Dont put in a long, complex expression
when MP just wants a number.
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MP is not very case-sensitive as regards
variables. The following are functions that are
available and they are case sensitive. Note that
all trig functions requires angles in radians and
all inverse trig functions return values in
radians. abs(x) - absolute value  exp(x) or
e(x) - exponential  log(x) - common logarithm
(base 10)  ln(x) - natural logarithm (base e)
 sqrt(x) - square root  sin(x) - trigonometric
sine  cos(x) - trigonometric cosine  tan(x) -
trigonometric tangent  csc(x) - trigonometric
cosecant  sec(x) - trigonometric secant  cot(x)
- trigonometric cotangent  asin(x) or arcsin(x)
- trigonometric arcsine  acos(x) or arccos(x) -
trigonometric arccosine  atan(x) or arctan(x) -
trigonometric arctangent  
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Hints There is no penalty for using the hints.
There is a bonus of 2 for not using the hints.
If you use the hints each answer you give is
worth a fraction of the points for the entire
problem. You could get most of the credit for a
problem even if you did not get the final
answer. If you answer a hint, you must answer it
correctly.
If you cant get an answer and think there is
something wrong with the program chances are 9 of
10 that the problem is you and not the program.
I try to work every problem before I release the
assignment. If you think there is a problem
e-mail me and I will look at it. When you enter
a comment into MP you are sending it to me. Keep
it clean!
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Scope of Physics 2211

• Classical Mechanics
• Mechanics How and why things move.
• Describing motion (KINEMATICS)
• What causes (changes to) motion? (DYNAMICS)
• Classical
• Not too fast (v ltlt c)
• Not too small (d gtgt atom)
• Most everyday situations can be described in
  these terms.
• Path of baseball
• Orbit of planets
• etc...

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Underpinnings of Science

• Models Simplification of Reality
• Reality is complicated.
• Models focus on whats important.
• (e.g., particle model)

• Measurements Anchors Models to Reality
• Reproducible, quantifiable experiments are
  crucial.
• Takes science beyond realm of individual
  experience

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Mechanics Tools

• Describing Mechanics Concepts
• Math
• Diagrams/Figures/Graphs
• Vocabulary/Technical Terms

• Motion Diagram

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Mechanics Vocabulary

• Position and Time
• Choice of
• Coordinate System

• Changes

Displacement
Time interval
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Vectors...

• An arrow is commonly used to represent a vector
  quantity moreover, there are two common ways to
  symbolize a vector quantity
• Boldface notation A
• Arrow notation

A
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Vector addition

• Consider the vectors A and B. Find A B.

B
B
A
A
A
C A B
B

• We can arrange the vectors as we want, as long as
  we maintain their length and direction!!

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• Which of the following corresponds to the
  diagram?
• 1. C B A
• 2. C A - B
• 3. C B - A
• 4. B C - A

C
B
A
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Vector Subtraction
Displacement
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Trajectory (Basketball)



Origin of Coordinates


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Mechanics Vocabulary

• How fast?
• Speed

distance traveled

• (Average)
• Velocity

Rate of Change of Position
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Trajectory (Basketball)



Origin of Coordinates


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Mechanics Vocabulary

• (Average) Acceleration

Rate of Change of Velocity
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Example 1.4 (Skier)
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A
Green arrows are vectors of for a runner circling
a track.
Which red vector best represents the average
acceleration at point A? (Press 9 if acceleration
is ZERO)
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Sprinter Motion Diagram
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Mechanics Vocabulary

• Speeding Up vs Slowing Down

• Accelerate vs Decelerate

• Positive acceleration vs Negative
  acceleration

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Kinematic Signs (Tactics Box 2.1)
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Problem Solving Strategy (Example 1.10)
A rocket is launched vertically with an
acceleration of 30 m/s2. It runs out of
fuel after 30 seconds. What is its
maximum altitude?
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Dimensions and Units...

• SI (Système International) Units
• mks L meters (m), M kilograms (kg), T
  seconds (s)
• cgs L centimeters (cm), M grams (gm), T
  seconds (s)
• British Units
• Inches, feet, miles, pounds, slugs...
• We will use mostly SI units, but you may run
  across some problems using British units. You
  should know how to convert back forth.

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Units of Kinematic (Motion) Quantities



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Converting between different systems of units
Useful Conversion factors 1 inch 2.54 cm 1
m 3.28 ft
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Converting between different systems of units
Useful Conversion factors 1 inch 2.54 cm 1
m 3.28 ft
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Dimensional Analysis

• An important tool to check your work. EASY TO
  USE!
• Example
• You do a problem and find for a distance d
• d vt 2 (velocity x time2)
• Units on left side L
• Units on right side (L / T) x T2 L x T
• Left units and right units dont match, so answer
  must be wrong!!
• Tip Dont do algebra with numbers.

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Tips

• Read !
• Before you start work on a problem, read the
  problem statement thoroughly. Make sure you
  understand what information is given, what is
  asked for, and the meaning of all the terms used
  in stating the problem.
• Watch your units !
• Always check the units of your answer, and carry
  the units along with your numbers during the
  calculation.
• Understand the limits !
• Many equations we use are special cases of more
  general laws. Understanding how they are derived
  will help you recognize their limitations (for
  example, constant acceleration).

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Recap

• Mastering Physics Homework Assignments
• Concepts of Motion
• Kinematics (Read Chapter 2)

On Tap