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 Applied Mechanics

8/9/2019 Applied Mechanics - 01

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Contents

1 - 2

What is Mechanics?

Fundamental Concepts

Fundamental Principles

Systems of Units

Method of Problem Solution

Numerical Accuracy

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 What is Mechanics?

1 - 3

Mechanics is the science which describes and predicts theconditions of rest or motion of bodies under the action offorces.

• Categories of Mechanics- !igid bodies

-  Statics- "#namics

- "eformable bodies- $luids

• Mechanics is an applied science - it is not an abstract or pure science butdoes not ha%e the empiricism found in other engineering sciences.

• Mechanics is the foundation of most engineering sciences and is anindispensable prere&uisite to their stud#.

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$undamental Concepts

-

 Space - associated with the notion of the position of a point ( gi%en interms of three coordinates measured from a reference point or origin.

• Time - definition of an e%ent re&uires specification of the time andposition at which it occurred.

•  Mass - used to characteri)e and compare bodies* e.g.* response toearth+s gra%itational attraction and resistance to changes intranslational motion.

•  Force - represents the action of one bod# on another. A force ischaracteri)ed b# its point of application* magnitude* and direction* i.e.*a force is a %ector &uantit#.

,n ewtonian Mechanics* space* time* and mass are absolute concepts*independent of each other. $orce* howe%er* is not independent of the other three.he force acting on a bod# is related to the mass of the bod# and the %ariation of

its %elocit# with time.

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$undamental (rinciples

•  Parallelogram Law

•  Principle of Transmissibility

•  Newton’s First Law ,f the resultant force on aparticle is )ero* the particle will remain at restor continue to mo%e in a straight line.

•  Newton’s Third Law he forces of action andreaction between two particles ha%e the samemagnitude and line of action with oppositesense.

•  Newton’s Second Law A particle will ha%e anacceleration proportional to a non)ero

resultant applied force.

am F  =

•  Newton’s Law of Gravitation wo particlesare attracted with e&ual and opposite forces*

22   , RGM  g mg W 

r  MmG F    ===

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0#stems of nits

1 -

•  Kinetic nits length* time* mass*and force.

• hree of the inetic units* referred to

as basic !nits* ma# be definedarbitraril#. he fourth unit* referredto as a derived !nit * must ha%e adefinition compatible with ewton+s2nd 4aw*

am F  =

•  "nternational System of nits 50,6he basic units are length* time* and

mass which are arbitraril# defined as themeter 5m6* second 5s6* and ilogram 5g6.$orce is the deri%ed unit*

( )        =

=

2s

m1kg1 N1

ma F 

• #S# $!stomary nitshe basic units are length* time* andforce which are arbitraril# defined as the

foot 5ft6* second 5s6* and pound 5lb6.Mass is the deri%ed unit*

sft1

lb1slug1   =

=a

 F m