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KINEMATICS OF MACHINES
1 UNIT
MECHANISMS AND MACHINES
Kinematics
Kinematics is the subject of mechanics which deals with the
motion of points, motion of rigid
bodies, and motion of group of rigid bodies without considering
the causes of motion. In
kinematics of machines the effect of forces won't be considered.
It only deals with geometrical
motion of bodies.
Machanism
If a number of bodies are assembled in such a way that the
motion of one causes constrained andpredictable motion to the
others, it is known as mechanism. It is the heart of the machine.
It
transmits and modifies motion.
A majority of mechanisms exhibit motion such that the parts move
in parallel planes.herefore,
these mechanisms are called planar mechanisms because their
motion is limited to two!
dimensional space.
Machine
A machine is a mechanism or combination of mechanisms which
imparts definite motion to the
parts also transmits and modifies available form of energy into
some useful work.
Structure
It is an assemblage of a number of resistant bodies "known as
members# having no relative motion
between them and meant for carrying loads having straining
action. A railway bridge, a roof truss,
machine frames etc., are the examples of a structure.
$achine $echanism
If the system is used with the objective of
transforming mechanical energy, then it is
called a machine
If the objective is to transfer or transform
motion without considering forces involved, the
system is said to be a mechanism
%very machine has to transmit motion because
mechanical work is associated with the motion,
and thus makes use of mechanisms
It is concerned with transfer of motion only
A machine can use one or more than one
mechanism to perform the desired function,
e.g. sewing machine has several mechanisms
It is not the case with mechanisms. A
mechanism is a single system to transfer or
transform motion
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Difference Between a Machine an a Structure
he following differences between a machine and a structure are
important from the subject point
of view &
. he parts of a machine move relative to one another, whereas
the members of a structure do not
move relative to one another.
(. A machine transforms the available energy into some useful
work, whereas in a structure no
energy is transformed into useful work.
). he links of a machine may transmit both power and motion,
while the members of a structure
transmit forces only.
$achines, $echanisms and *tructures are composed of individual
eliments called as links.
+ink is defined as the resistant body or a group of resistant
bodies with rigid connections
preventing their relative motion is known as link.
