Engineering Mechanics

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Introduction

The state of rest and state of motion of the bodies under the action of different forces has
engaged the attention of philosophers, mathematicians and scientists for many centuries. The
branch of physical science that deals with the state of rest or the state of motion is termed as
Mechanics. Starting from the analysis of rigid bodies under gravitational force and simple
applied forces the mechanics has grown to the analysis of robotics, aircrafts, spacecrafts under
dynamic forces, atmospheric forces, temperature forces etc.
Archimedes (287–212 BC), Galileo (1564–1642), Sir Issac Newton (1642–1727) and
Einstein (1878–1955) have contributed a lot to the development of mechanics. Contributions
by Varignon, Euler, D. Alembert are also substantial. The mechanics developed by these
researchers may be grouped as
(i) Classical mechanics/Newtonian mechanics
(ii) Relativistic mechanics
(iii) Quantum mechanics/Wave mechanics.
Sir Issac Newton, the principal architect of mechanics


CLASSIFICATION OF ENGINEERING MECHANICS
Depending upon the body to which the mechanics is applied, the engineering mechanics
is classified as
(a) Mechanics of Solids, and
(b) Mechanics of Fluids.
The solid mechanics is further classified as mechanics of rigid bodies and mechanics of
deformable bodies. The body which will not deform or the body in which deformation can be
neglected in the analysis, are called as Rigid bodies. The mechanics of the rigid bodies dealing
with the bodies at rest is termed as Statics and that dealing with bodies in motion is called

Dynamics. The dynamics dealing with the problems without referring to the forces causing
the motion of the body is termed as Kinematics and if it deals with the forces causing motion
also, is called Kinetics.


Mass
The quantity of the matter possessed by a body is called mass. The mass of a body will
not change unless the body is damaged and part of it is physically separated. When a body is
taken out in a spacecraft, the mass will not change but its weight may change due to change in
gravitational force. Even the body may become weightless when gravitational force vanishes
but the mass remain the same.

Time
Time is the measure of succession of events. The successive event selected is the rotation
of earth about its own axis and this is called a day. To have convenient units for various
activities, a day is divided into 24 hours, an hour into 60 minutes and a minute into 60 seconds.
Clocks are the instruments developed to measure time. To overcome difficulties due to irregularities
in the earth’s rotation, the unit of time is taken as second which is defined as the
duration of 9192631770 period of radiation of the cesium-133 atom.