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Engineering 36
Chp 1
Introduction
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
[email protected]
Engineering-36: Vector Mechanics - Statics
1
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Learning Statics
There is ONLY ONE WAY to Learn
Statics
Work LOTS of Problems
• Work Thru, and UNDERSTAND, all
Sample Problems
• Work Chp Problems for Which the Book
Provides Answers
– Handily Located in the Back of the Book; See
“ANSWERS TO SELECTED PROBLEMS”
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Class Structure – ENGR36
Lecture TTh 1:00-1:50p
• PowerPoint Instruction-Presentation on The
Interactions of Forces (Push/Pull) and
Moments (Twists) on NONmoving structures
Lab – TTh 2:00-3:15p
• Tu: WhiteBoard Example Solutions to
Problems Similar to the LPS (HomeWork)
Problems
• Th: Work in Computer Lab 3906A on the
Mastering Engineering LPS Problems
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
If you can’t Make the Lab Every
time... Don’t Worry
I will post my solved Examples on the
ENGR36 Course WebPage
Any Student can Work at his/her own
Time & Location in place of the lab AS
LONG AS the LPS are Submitted to
Mastering Engineering ON TIME
If a student can not make the Lab
Session, I suggest forming an ENGR36
study Group outside of class times
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Mastering Engineering
http://www.masteringengineering.com/
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Mastering Engineering
http://www.masteringengineering.com/site/register/new-students.html
Pick One, then Continue
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Mastering Engineering: $60.50
http://www.mypearsonstore.com/bookstore/product.asp?isbn=0132915545&xid=PSED
An Access Code is provided with the
TextBook Available in the BookStore
Students who purchased the book from
another source can purchase Stand-Alone
Mastering Engineering for $60.50
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
If you received a Course ID
from your instructor, click Yes,
enter your Course ID and click
Continue.
CHABOTENGR36FA12
Engineering-36: Vector Mechanics - Statics
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If you DO NOT have a Course
ID, follow the instructions on
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[email protected] • ENGR-36_Lec-01_Introduction.ppt
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If so, enter the appropriate
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Use “W” Number
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contact your instructor or click Skip
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(You can enter your Student ID later.)
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Registering Tips Video
http://www.masteringsupport.com/video
s/registration_tips/registration_tips.html
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Product Design
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Product Design
Requirements/Goals
• The goal of this
phase is to figure out
exactly what the
customer wants
Specification
• describe exactly
what the product will
do and how it will
perform
Engineering-36: Vector Mechanics - Statics
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• focus on WHAT the
product is supposed
to do, not HOW it is
supposed to do it
Design
• Conceptual →
Generate Broad
Concept Solutions
• Preliminary →
Choose 2-3
Concepts for Testing
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Product Design
Design
• Detailed → Select
“winning” solution
• Sweat details →
select materials,
Perform engineering
analyses, make
Engineering DWGs,
determine production
and test methods
Implement
• Make a PHYSICAL
Prototype unit
Engineering-36: Vector Mechanics - Statics
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Test
• Test every item in
the performance
specification →
Possible OutComes
– The product does
NOT meet the spec
– The product meets the
spec but the spec was
WRONG
– customer CHANGED
his/her mind
– product MEETS the
spec and customer
is HAPPY
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Analysis
Goal
• What EXACTLY do we want to determine?
– Suggest including the UNITS for the “answer”
Given
• Summarize KNOWN conditions and
previously collected DATA
Assume (this HAS to be done)
• Make an analytical MODEL
• List Important assumptions
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Assumption Digression
BMayer 2001 JVST Paper
• See
ENGR45
for More
Details
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Assumption Digression
PARTIAL
Assumption List
• 100% Vapor
Saturation at Bubble
Edge
• Gases in bubble
behave as perfect
gases
• Bubbles are
Spherical
– Radial Symmetry
Engineering-36: Vector Mechanics - Statics
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• Diffusion Coefficient
is Constant
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Analysis
Draw Diagram if Possible
• Sketching a Diagram is critical
• Take time to make a Sketch that is Clear
and in Proportion (roughly to scale)
Create Math Model
• Make equations based on known scientific
(physics, chem) or engineering principles
Solve Math Model
• Math Processors (MATLAB, Excel) helpful
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Analysis
Check Results
• Make a “Reality
Check” on Results
• Test with KNOWN
inputs and compare
to the KNOWN result
• Test with a WIDE
range of inputs to test
“robustness”
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Mechanics – General
Mechanics The Physical Science Which
Describes Or Predicts The Conditions Of
REST Or MOTION For BODIES Under The
Action Of FORCES and/or MOMENTS
• Some Classes of Mechanics Analysis
– Rigid Bodies
Statics → NO Motion
Dynamics → Moving in General
– Deformable Bodies → Forces Interact with MATERIAL
Properties
3rd yr course at the University Level
– Fluid Mechanics → almost always deforming materials
Compressible → gas
Incompressible → liquids
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Rigid Body – Special Case
Rigid-Body Analysis Considers All Bodies To
Be Perfectly Stiff → NO Deformation
• Not Strictly True In Practical Situations as All
Physical Structures Deform (However Slightly)
When Subjected to Force-Loading.
– Rigid Body Analysis Applies When Deformations Are
“Small” and so Do Not “Significantly” Affect The
Conditions Of Equilibrium Or Motion
i.e., Can Neglect Deformation For Equil/Motion Analysis
Rigid Body ≡ A Body is Considered Rigid
When The Relative Movement Between Its
Parts is Negligible
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Statics – Further Special Case
Statics Is A SubClass of Rigid Body
Mechanics Analysis
Statics ≡ Study Of Equilibria Of A System
Without Regard To Inertia Forces Or Velocity
Dependent Forces → No or Const. Motion
• Apply Newton’s 2nd Law Using Vector Notation
F ma
but a 0
F 0!
• Consequences of Static Rigid-Body Conditions
– System Accelerations Are ZERO
– Force InterActs with CONFIGURATION Only
– governing equations are ALGEBRAIC In Nature
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Statics - Fundamental Concepts
Static Analysis is Based on Incompletely
Defined, But Thoroughly Familiar Concepts
1. SPACE ≈ The Geometric Region Occupied By
Bodies Whose Positions Are Described By
Linear and Angular Measurements
Cartesian
Relative to a Coordinate System
Space
2. TIME ≈ The Measure Of The
Succession Of Events
3. MASS ≈ The Measure of the Body’s Inertia,
Which Is Its Resistance to a Change Of Motion.
Sometimes Called "Quantity Of Matter“
4. FORCE ≈ The Action Of One Body On Another
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Newtonian Mechanics
Sir Isaac Newton (1642-1727) Was the First
Person To Mathematically Describe the
Physical Relationship Between the
Fundamentals
•
In Newtonian Mechanics Space, Time, And Mass
Are Absolute, And Independent Of Each Other
Newton’s Laws
1. Objects At Rest Will Stay At Rest, and
Objects In Motion Will Stay In Motion In A
Straight Line Unless Acted Upon By An
Unbalanced Force (Resultant Force = 0).
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Newtonian Mechanics cont.
2. Force Is Equal To Body
Mass Times its
Acceleration; Mathematically
F ma
Note: for STATIC; i.e.,
NonMoving, systems a = 0
3. For Every Action There
Is Always An Opposite
And Equal Reaction that
is CoLinear
Engineering-36: Vector Mechanics - Statics
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Sir Issac Newton
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Systems of Units
Base units For Static Analysis
System
SI Units
US Customary Units
Length
Mass
Time
Meter (m)
Kilogram (kg)
Second (s)
Foot (ft)
Slug (slug)
Second (s)
FORCE is the Most Important Derived Unit
• Find the SI Consistent Force Unit by Applying a
Unitary Acceleration, a, of 1 m/s2
– Funit = (1 kg)•(1 m/s2) = 1 N (newton)
• Recall for a Weight, the Acceleration is g.
One kg “weighs”:
– W = mg = (1 kg)•(9.81 m/s2) = 9.81 N
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Tips on Units
Maintain Units Through ALL Calculations
• Serves as A Consistency Check
Use SI Prefixes (Next Slide) to Avoid
Scientific Notation
• But for Complex Calculations, Convert back to
Non-Prefixed SI Units to Avoid Order-of
Magnitude Errors
Separate 3-Digit Groups with a Space,
NOT a Comma
• YES → 45 611 m
Engineering-36: Vector Mechanics - Statics
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NO → 789,321 s
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
SI prefixes
Factor
Name
Symbol
Factor
Name
Symbol
1024
yotta
Y
10-1
Deci
d
1021
zetta
Z
10-2
Centi
c
1018
exa
E
10-3
milli
m
1015
peta
P
10-6
micro
µ
1012
tera
T
10-9
nano
n
109
giga
G
10-12
pico
p
106
mega
M
10-15
femto
f
103
kilo
k
10-18
atto
a
102
hecto
h
10-21
zepto
z
101
deka
da
10-24
yocto
y
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
US Units lbs vs. slugs
In The US Customary System the Unit of
FORCE Pound (lb)
• F = ma
and
1 lb = m•(1 ft/s2)
• Thus m = 1 lb•s2/ft = 1 slug
Weight of 1 slug by gravity?
• W = mg
Where
g = 32.2 ft/s2
• Thus Wslug = 32.2 slug•ft/s2 = 32.2 lb
Summary
• 1 lb Is The Force Required To Give A Mass Of 1
Slug An Acceleration Of 1 ft/s²
• 1 lb Is The Force Required To Give A Mass Of
1/32.2 Slug An Acceleration Of 32.2 ft/s²
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Unit Conversion
As Noted Before Unit-Consistency Is Critical
for Arriving at a Proper Answer
To Convert From One Set of Units to Another
use the “Cross-Out” Division Method
• e.g. Given a Speed, , of 60 mph; find ft/s & m/s
– Given From ref Bk: 1mi = 5280ft
and 1m = 3.281ft
fps 60
and
1hr = 3600s
m i 5280ft 1hr
ft
88
hr m i 3600s
s
m
ft 1m
26.82
SI 88
s
s 3.281ft
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Numerical Precision
Precision is Determined by The PHYSICAL
Situation, NOT the CALCULATOR
• In Particular, A Computed Result Can be NO MORE
Precise Than The LEAST Accurate of
– Physically Measured (or Derived from Measured) DATA
– The Precision of the Calculation
This Was Issue in the SlideRule Days, But Rarely Now
• Example: Find the Average of this Physically Reliable
Data Set (13.47, 9.9, 7.803)
avg
13.47 9.9 7.803
10.391 (by calc)
3
10.4 (reliably)
– In This Example, the Middle Value Governs Precision
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Numerical Precision, cont.
It is Physically difficult to Make Precise and
Reliably-Accurate Measurements to Better
Than 1 part per 1 000 (1 ppt); or about 0.1%
• Most Practicing Engineers are Very Skeptical of
Any Data/Calculations Presented at
1 part in 10 000 (or more)
Good “Rule of Thumb”
• 4 Figures For Values Starting With No. 1
– Called “3½” Significant Figures
• 3 Figures In All Other Cases
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
CoOrdinate Systems
The CoOrd TriAd is Defined by Your
RIGHT Hand → Rt-Hand Rule
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Right-Hand Rule
Thumb points in the positive x direction
Index finger points in
the positive y direction
Middle finger points in
the positive z direction
Used to define positive rotation
• Point thumb in the positive direction along
the axis which is perpendicular to the plane
of rotation
• The fingers point in the direction of
positive rotation
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Vectors
VECTOR ≡ Parameter Possessing Magnitude
And Direction, Which Add According
To The Parallelogram Law
• Examples: Displacements,
Velocities, Accelerations, FORCES
SCALAR ≡ Parameter Possessing
Magnitude But Not Direction
• Examples: Mass, Volume, Temperature
Vector Classifications
• FIXED Or BOUND Vectors Have Well Defined
Points Of Application That CanNOT Be Changed
Without Affecting An Analysis
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Vectors cont.
• FREE Vectors May Be Moved In Space Without
Changing Their Effect On An Analysis
• SLIDING Vectors May Be Applied Anywhere Along
Their Line Of Action Without Affecting the Analysis
• EQUAL Vectors Have The Same Magnitude And
Direction
• NEGATIVE Vector Of a Given Vector Has The
Same Magnitude but The Opposite Direction
Equal Vectors
Negative Vectors
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Vector Representations
MagAngle
Unit Vectors
• Length of “Unit”
Vectors (i, j, k) = 1
• Magnitude ≡ ||V||
= Geometric Length
• Space Angles:
θx, θy, θz
Engineering-36: Vector Mechanics - Statics
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More on Vector
“DeComposition” in
future lectures
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering Drawings
Formal Drawing
Informal Drawing
• Contains all
information needed
for FABRICATION or
ASSEMBLY
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Free-Body Diagrams
SPACE DIAGRAM
A Sketch Showing
The Physical
Conditions Of The
Problem
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FREE-BODY
DIAGRAM A
Sketch Showing
ONLY The Forces
Acting On The
Selected Body
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Suggested Review → Trig
Solving Statics Problems Often Involves
Non-Right Triangle Geometry. Some Useful
Relationships (See your Math Book)
Law of Sines
Law of Cosines
a=13, c=17, B=43°
a=11, b=19, C=101°
• A=31.4°, C=105.6°
b=24
Engineering-36: Vector Mechanics - Statics
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• c = 23.7
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Battle of the TriAngle
If 3 SIDE-LENGHTS are
known → Use Cos-Law to
Find any angle
• Solve Eqn at Right for cos(c)
If 2 SIDE-LENGTHS and the
Included Angle are known
→ Use Cos-Law to find the Opp Side-Length
Use Sin-Law for
• 2-ANGLES & 1-SIDE known
• 2-SIDES & NonIncluded Angle
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Done for 1st Meeting
Please see
me if you
would like to
ADD
Static Loading
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Engineering 36
Appendix
Bruce Mayer, PE
Registered Electrical & Mechanical Engineer
[email protected]
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Newtonian Mechanics cont.
2. Force Is Equal To Body Mass Times its
Acceleration; Mathematically
F ma
3. For Every Action There Is Always An Opposite
And Equal Reaction
Newton’s Law of Gravitation
GMm
F
( F a SCALAR)
2
r
M
F
F mutual force of attraction between 2 particles
G universal constant known as the
constant of gravitation
M, m masses of the 2 particles
r distance between the 2 particles
Engineering-36: Vector Mechanics - Statics
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
-F
m
Weight
Consider An Object of mass, m, at Height, h,
Above the Surface of the Earth, Which as
Radius R
• Then the Force on the Object (e.g., Yourself)
GMm
F
2
R h
GM
but R h F m 2 m g
R
This Force Exerted by the Earth is called Weight
• While g Varies Somewhat With the Elevation &
Location, to a Very Good Approximation
– g 9.81 m/s2 32.2 ft/s2
Engineering-36: Vector Mechanics - Statics
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W mg
Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt
Earth Facts
D 7 926 miles (12 756 km)
M 5.98 x 1024 kg
• About 2x1015 Empire
State Buildings
Density, 5 520 kg/m3
• water 1 027 kg/m3
• steel 8 000 kg/m3
• glass 5 300 kg/m3
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Bruce Mayer, PE
[email protected] • ENGR-36_Lec-01_Introduction.ppt