ME 221 StaticsFall 2003

Mr. Hinds

3523 EB

hinds@msu.edu

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

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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

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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

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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