me 221 statics fall 2003 mr. hinds 3523 eb [email protected]
Post on 22-Dec-2015
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TRANSCRIPT
ME221 Lecture 1 2
Administrative Details• Syllabus will be posted on the web
– www.angel.msu.edu (Angel)
• Lecture attendance – Web will be used for announcements but not all important
announcements given in class may be posted on the web
– Bring books to class for example problems• Sample problems will be an integral part of lecture
• Lecture behavior– Class size requires professional conduct
ME221 Lecture 1 3
Administrative Details cont.• Exams
– Dates set and given on syllabus• first test date set for 100% refund drop date
– Format• closed book, closed notes, calculator
– Excused absences: See syllabus– Philosophy
• Most problems like HW; some problems conceptually same as HW but somewhat different
ME221 Lecture 1 4
Administrative Details cont.• Homework & quizzes
– solutions will be posted– all or partial problems will be graded
– lecture quizzes used as “scrimmages”• quizzes in the last 15-20 minutes of lecture
• similar to assigned homework
• generally announced - some unannounced
ME221 Lecture 1 5
Administrative Details cont.
Questions??
ME221 Lecture 1 6
ENGINEERING…
The Future and the Challenges…..??
ME221 Lecture 1 7
Problem Solving Strategy
1 - Modeling of physical problem (free body diagram)
2 - Expressing the governing physical laws in mathematical form
3 - Solving the governing equations
4 - Interpretation of the results
ME221 Lecture 1 8
Mechanics Reform• Textbook offers a departure from past standards
– recognizes the power of computer software in solving problems
– before using the software, the problem must be properly posed
• posing the problem will be emphasized in this class
• MathCAD, MatLab, Maple, Mathmatica, VB, etc.
• calculators may be effectively utilized as well
ME221 Lecture 1 9
Mechanics Reform cont.
• Software does not help with:– envisioning the forces
• Software helps us with:– trigonometry– units conversion– systems of equations– iterative problems for design purposes
– applying the proper laws of physics
ME221 Lecture 1 10
Mechanics• Broadly defined as the study of bodies that
are acted upon by forces.
– deformable bodies– fluids
• Types of bodies– particles (considered rigid bodies)– rigid bodies - relative distance between any two
points remains constant throughout motion
ME221 Lecture 1 11
Mechanics Overview
Statics Rigid Static
Mech Matl Deformable Static
Dynamics Rigid Dynamic
Fluid Dyn Deformable Dynamic
ME221 Lecture 1 12
And now ...
Statics
ME221 Lecture 1 13
Chapter 1: Measurement•Newton’s Laws of Motion•Space and Events
•Vectors and Scalars
•SI Units (Metric)
•U.S. Customary Units•Unit Conversion
•Scientific Notation•Significant Figures
ME221 Lecture 1 14
Basics: Newton’s Laws•Every body or particle continues in a state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces acting upon it.
(Law of Inertia)
•The change of motion of a body is proportional to the net force imposed on the body and is in the direction of the net force.
F=ma
•If one body exerts a force on a second body, then the second body exerts a force on the first that is equal in magnitude, opposite in direction, and collinear.
ME221 Lecture 1 15
•Law of Universal Gravitation:
Any two particles are attracted to each other with a force whose magnitude is proportional to the products of their gravitational masses and inversely proportional to the square between them.
F=Gm1m2/r2
where G = 66.73 x 10-12 m3/kg-s2
ME221 Lecture 1 16
Basics• Space -- we need to know the position of particles
• Event -- position at a given time
xz
y mi
ME221 Lecture 1 17
Basics cont.
– vectors must have direction specified• e.g., velocity, force, acceleration
• Mass -- a scalar that characterizes a body’s resistance to motion
• Force -- (vector) the action of one body on another through contact or acting at a distance
• Two broad quantities– scalars have no direction associated with them
• e.g., temperature, mass, speed, angle
ME221 Lecture 1 18
International System of Units:The SI systemLength meters m
Time seconds s
Mass kilogram kg
Force Newton N 1 kg m/s2
See table 1-1 for prefixesCompound units
Remember: Speed = distance/time
so in SI units, speed is measured in m/s
ME221 Lecture 1 19
U.S. Customary Units
Length foot ft
Time seconds s
Mass slug slug
Force pound lb slug ft/s2
*Remember: W= mg
where g = 32.17 ft/s2
ME221 Lecture 1 20
Numerical Answers
– equal 5: then all digits after it are dropped
• Significant figures– Use 3 significant digits– If first digit is 1, then use next 3
• Rounding off the last significant digit– less than 5: all digits after it are dropped
– greater than 5 or equal 5 followed by a nonzero digit: round up
ME221 Lecture 1 21
END OF BASICS