Chapter 1 engineering mechanics

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WEEK 1_01

BKF 1313

ENGINEERING MECHANICS

STATIC

INTRODUCTION TO MECHANICS



Introduction to MechanicsIntroduction to Mechanics



What is Mechanics?

� Study of what happens to a ³thing´ (the technical name is

³body´) when FORCES are applied to it.

� Either the body or the forces could be large or small.



What is Mechanics?

� Mechanics is the science which describes andpredicts the conditions of rest or motion of bodies under the action of forces.

� Categories of Mechanics:

- Rigid bodies- Statics

- Dynamics

- Deformable bodies

- Fluids

� Mechanics is an applied science - it is not an abstractor pure science but does not have the empiricism

found in other engineering sciences.

� Mechanics is the foundation of most engineering sciences

and is an indispensable prerequisite to their study.



Branches of Mechanics

Statics Dynamics

Rigid Bodies

(Things that do not change shape

Deformable Bodies

(Things that do change shape)

Incompressible

Compressible

Fluids

Mechanics

Type title here



What may happen if statics is not applied

properly



Fundamental Concepts

� Space - associated with the notion of the position of a point P given in termsof three coordinates measured from a reference point or origin.

� Time - definition of an event requires specification of the time and position

at which it occurred.

� Mass - used to characterize and compare bodies, e.g., response to earth¶s

gravitational attraction and resistance to changes in translational motion.

� Force - represents the action of one body on another. A force is

characterized by its point of application, magnitude, and direction, i.e., a

force is a vector quantity.

In Newtonian Mechanics, space, time, and mass are absolute concepts,

independent of each other. Force, however, is not independent of the other

three. The force acting on a body is related to the mass of the body and the

variation of its velocity with time.



Fundamental Principles

� P arallelogram Law

� P rinciple of Transmissibility

� Newton¶s First Law: If the resultant force on a

particle is zero, the particle will remain at rest

or continue to move in a straight line.

� Newton¶s Third Law: The forces of action and

reaction between two particles have the same

magnitude and line of action with opposite

sense.

� Newton¶s Second Law: A particle will have

an acceleration proportional to a nonzero

resultant applied force.amF TT

!

� Newton¶s Law of Gravitation: Two particles

are attracted with equal and opposite forces,

22,

R

Gg g W

r

G !!!



SYSTEMS OF UNITS

� Four fundamental physical quantities.

� Length, mass, time, force.

� One equation relates them, F = m * a

� We use this equation to develop systems of units

� Units are arbitrary names we give to the physical quantities.



UNIT SYSTEMS

� Define 3 of the units and call them the base units.

�Derive the 4th unit (called the derived unit) using

F = m * a.� We will work with one unit system in static¶s: SI.





RULES FOR USING SI SYMBOLS

� No Plurals (e.g., m = 5 kg not kgs )

� Separate Units with a � (e.g., meter second = m � s )

� Most symbols are in lowercase ( some exception are N,

Pa, M and G)

� Exponential powers apply to units , e.g., cm2 = cm � cm

� Other rules are given in your textbook



NUMERICAL CALCULATIONS

� Must have dimensional homogeneity. Dimensions haveto be the same on both sides of the equal sign, (e.g.distance = speed v time.)

� Be consistent when rounding off.

- greater than 5, round up (3528 3530)- smaller than 5, round down (0.03521 0.0352)

- equal to 5,

� Use an appropriate number of significant figures (3 for

answer, at least 4 for intermediate calculations).



PROBLEM SOLVING STRATEGY:

IPE, A 3 Step Approach

1. Interpret: Read carefully and determine what is given and

what is to be found/ delivered. Ask, if not clear. If

necessary, make assumptions and indicate them.

2. Plan: Think about major steps (or a road map) that you will

take to solve a given problem. Think of

alternative/creative solutions and choose the best one.

3. Execute: Carry out your steps. Use appropriate diagrams andequations. Estimate your answers. Avoid simple

calculation mistakes. Reflect on / revise your work.



Chapter 1 engineering mechanics

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