MECHANICS - the Study of Forces and Their Effects

INTRODUCTION

ENGINEERING AND MECHANICS

MECHANICS - THE STUDY OF FORCES AND THEIR EFFECTS STATICS - the study of objects in equilibrium DYNAMICS - the study of objects in motion

LEARNING MECHANICS

THE MAIN GOAL - understand the principles well enough to apply them to new situations PROBLEM SOLVING: - Identify the information that is given and the information/answer to determine - Develop the strategy – identify the principles and equations to apply, and draw diagrams if possible - Try to predict the answer - Solve the equations and interpret results (and compare them with the prediction)

ENGINEERING APPLICATIONS Essential aspects of engineering: - Design (choose values of parameters to satisfy stated design criteria) - Safety (choose values of parameters to satisfy stated safety requirements) FUNDAMENTAL CONCEPTS

NUMBERS Engineering measurements, calculations and results are expressed in numbers. SPACE AND TIME Space – geometric region occupied by bodies whose positions are described by linear and angular measurements relative to a coordinate system. Time – measure of the succession of events; basic quantity in dynamics, not directly involved in statics. Mass – measure of the inertia of a body (resistance to a change of a velocity), or the quantity of matter in a body; also, the property of every body by which it experiences mutual attraction to other bodies. Force – action of one body to another; tends to move a body in the direction of its action; vector quantity. Particle – body of negligible dimensions (may be analyzed as a point mass) Rigid – relative movements between its part are negligible for the purpose in hand body

NEWTON’S LAWS I – A particle remains at rest or continues to move in a straight line with uniform velocity if there is no unbalanced force acting on it. II – The acceleration of a particle is proportional to the resultant force acting on it and is in the direction of this force. III – The forces of action and reaction between interacting bodies are equal in magnitude, collinear, and opposite in direction. UNITS DIMENSIONAL SI UNITS U.S. CUSTOMARY UNITS QUANTITY SYMBOL UNIT SYMBOL UNIT SYMBOL Mass M kilogram kg slug -

Lengt L Base meter m foot ft units Base h units Time T second s second s Force F newton N pound lb

Derived units: 1 N = 1 kg-m/s2 SI Units 1 slug = 1 lb-s2/ft U.S. Customary Units

The common prefixes used in SI units and the multiples they represent Prefix Abbreviation Multiple pico- p 10-12 nano- n 10-9 micro-  10-6 mili- m 10-3 kilo- k 103 mega- M 106 giga- G 109 tera- T 1012

ANGULAR UNITS QUANTITY UNIT SYMBOL UNIT SYMBOL Both SI and U.S. Angle radian rad degree  or deg Customary units

CONVERSION OF UNITS

LENGTH 1 in = 25.4 mm 1 ft = 12 in = 0.3048 m 1 mi = 5280 ft = 1609 m 1 m = 3.281 ft 1 km = 0.6214 mi TIME 1 min = 60 s 1 hr = 60 min 1 day = 24 hr MASS 1 slug = 14.59 kg 1 kg = 0.0685 slug FORCE 1 lb = 4.448 N 1 N = 0.2248 lb ANGLE 2  rad = 360 1 rad = 57.3 1 = 0.01745 rad