# Engineering Mechanics Statics Engineering

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```					Engineering Mechanics
Statics

ECS221
A. J. Levy
Course Structure

 M,W lecture + F clinic or exam
 Graded homework (13%)

 Four class exams (54%)

 Final exam (33%)

 Course evaluation
Introduction
Primitive concepts
 Space (coordinate system, length;
scalar)
 Time (definition of event; scalar)

 Mass (resistance to motion,
attraction to the earth; scalar)
 Force (direct contact, action at-a-
distance; vector)
Idealizations in
Mechanics
   The mass point or particle
(position and mass)
   The rigid body (position, size
and mass)
   The deformable body (position,
size, mass and deformability)
Fundamental Principles
   Parallelogram law for addition of
forces (and vectors)
Fundamental Principles
   Transmissibility (bodies must be
rigid!!!)

=
pushing     =    pulling
Fundamental Principles
   Newton’s first law

“Every body continues in a state
of rest, or of uniform motion in a
right line, unless it is compelled
to change that state by forces
impressed on it.”
Fundamental Principles
   Newton’s second law

“The change of motion is
proportional to the motive force
impressed; and is made in a
direction of the right line in
which the force is impressed.”
Fundamental Principles
   Newton’s third law

“To every action there is always
opposed an equal reaction: or,
the mutual actions of two bodies
upon each other are always
equal, and directed to contrary
parts.”
Fundamental Principles
   Newton’s law of gravitation

“Two particles will be attracted
toward each other along their
connecting line with a force
whose magnitude is given by:
m1m2
FG 2
r
“The weight of a body”
 GM               GM m  gm
F        2
m    W  2 
 (R  h)         R 

m
R+h
M       R
Systems of Units
   International (mks)
Force is derived unit.    1N1kg1m s2

   American (fps)
Mass is derived unit. 1slug 1lb 1ft s2
1lbm 1lb 32.2ft s2

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