ME 221 Statics Fall 2003 Mr. Hinds 3523 EB

ME221Lecture 12 Administrative Details Syllabus will be posted on the web – (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

ME221Lecture 13 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

ME221Lecture 14 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 minutes of lecture similar to assigned homework generally announced - some unannounced

ME221Lecture 15 Administrative Details cont. Questions??

ME221Lecture 16 ENGINEERING… The Future and the Challenges…..??

ME221Lecture 17 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

ME221Lecture 18 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

ME221Lecture 19 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

ME221Lecture 110 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

ME221Lecture 111 Mechanics Overview Statics RigidStatic Mech Matl Deformable Static Dynamics Rigid Dynamic Fluid Dyn Deformable Dynamic

ME221Lecture 112 And now... Statics

ME221Lecture 113 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

ME221Lecture 114 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.

ME221Lecture 115 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=Gm 1 m 2 /r 2 where G = x m 3 /kg-s 2

ME221Lecture 116 Basics Space -- we need to know the position of particles Event -- position at a given time x z y mimi

ME221Lecture 117 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

ME221Lecture 118 International System of Units:The SI system Lengthmetersm Timesecondss Masskilogramkg ForceNewtonN1 kg m/s 2 See table 1-1 for prefixes Compound units Remember: Speed = distance/time so in SI units, speed is measured in m/s

ME221Lecture 119 U.S. Customary Units Lengthfootft Timesecondss Massslugslug Forcepoundlbslug ft/s 2 *Remember: W= mg where g = ft/s 2

ME221Lecture 120 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

ME221Lecture 121 END OF BASICS