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ME 221 Statics Fall 2003PowerPoint Presentation

ME 221 Statics Fall 2003

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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

Lecture 1

Administrative Details cont.

- Exams
- Dates set and given on syllabus
- first test date set for 100% refund drop date

- Dates set and given on syllabus

- Format
- closed book, closed notes, calculator

- Excused absences: See syllabus
- Philosophy
- Most problems like HW; some problems conceptually same as HW but somewhat different

Lecture 1

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

Lecture 1

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

Lecture 1

Mechanics Reform

- Textbook offers a departure from past standards
- recognizes the power of computer software in solving problems

- MathCAD, MatLab, Maple, Mathmatica, VB, etc.

- calculators may be effectively utilized as well

- before using the software, the problem must be properly posed
- posing the problem will be emphasized in this class

Lecture 1

Mechanics Reform cont.

- Software helps us with:
- trigonometry
- units conversion

- Software does not help with:
- envisioning the forces

- systems of equations
- iterative problems for design purposes

- applying the proper laws of physics

Lecture 1

Mechanics

- Broadly defined as the study of bodies that are acted upon by forces.

- Types of bodies
- particles (considered rigid bodies)

- rigid bodies - relative distance between any two points remains constant throughout motion

- deformable bodies
- fluids

Lecture 1

Static

Statics

Static

Deformable

Mech Matl

Dynamic

Rigid

Dynamics

Dynamic

Fluid Dyn

Deformable

Mechanics OverviewLecture 1

- Newton’s Laws of Motion

- Space and Events

- Vectors and Scalars

- SI Units (Metric)

- U.S. Customary Units

- Unit Conversion

- Scientific Notation

- Significant Figures

Lecture 1

- 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.

Lecture 1

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

Lecture 1

mi

x

z

Basics- Space -- we need to know the position of particles

- Event -- position at a given time

Lecture 1

Basics cont.

- vectors must have direction specified
- e.g., velocity, force, acceleration

- Two broad quantities
- scalars have no direction associated with them
- e.g., temperature, mass, speed, angle

- scalars have no direction associated with them

- 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

Lecture 1

International System of Units:The SI system

- Length meters m
- Time seconds s
- Mass kilogram kg
- Force Newton N 1 kg m/s2
- See table 1-1 for prefixes

Compound units

Remember: Speed = distance/time

so in SI units, speed is measured in m/s

Lecture 1

- Length foot ft
- Time seconds s
- Mass slug slug
- Force pound lb slug ft/s2

- *Remember: W= mg

- where g = 32.17 ft/s2

Lecture 1

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

Lecture 1

Lecture 1

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