Mechanics of Materials Introduction

Introduction to Mechanics of Materials
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The subject of materials mechanics is complementary to the subject of
engineering mechanics. The difference between them is that engineering
mechanics examines the relationship between forces and bodies, considering
that bodies are rigid (no deformation occurs in them), while materials
mechanics examines the effect of forces on the inside of bodies, and bodies
are not considered rigid. A simple change in the shape of bodies is very
important in studying the resistance of materials. The impact may be
elongation, shrinkage, bending or deformation in shape (deformation shear).
Mechanics of materials is a study of the relationship between the external
loads applied to a body and the stress and strain caused by the internal loads
within the body.Mechanics of Materials answers two questions :
Is the material strong enough?
Is the material stiff enough ?
If the material is not strong enough, your design will break
If the material isn't stiff enough, your design probably won't function the
way it's intended to
-The main objective of the study of the mechanics of materials is to provide
the engineer with the means of analyzing and designing various machines
and load bearing structures.Equilibrium
The term "equilibrium" or, more specifically, "static equilibrium" is used to
describe an object at rest. To maintain equilibrium, it is necessary to satisfy
Newton's first law of motion, which requires the resultant force acting on a
particle to be equal to zero. This condition may be stated mathematically as:
"When a body is in equilibrium, the resultant of all forces acting on it is zero"
which leads to:
(Summation of internal and external forces and moments equals to zero).Free body diagram F.B.D
A free body diagram is a representation of an object with all the forces acting
on it. The external environment (the floor the body sits on), as well as the
forces that the body exerts on other bodies, are omitted in the free-body
diagram
Free body diagrams are used to visualize forces and moments applied to a
body and to calculate reactions in mechanics problems. These diagrams are
frequently used to determine the loading of individual structural components
and to calculate internal forces within a structure.finding the angle of two lines perpendicular their horizontal and
vertical components .When I have two straight lines perpendicular and I want to find the angle of
one of the straight lines with its horizontal and vertical component, the angle
between one of the two straight lines with its vertical component (make it AB
as in example 1) is the same as the angle between the other straight line
(the vertical straight line with it but CD) with its horizontal component The same applies to the other angle, where the angle with straight AB and
its horizontal component is the same as the angle between straight CD
(the straight line perpendicular to it) with its vertical component.
That is, they exchange the angles of their components.

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