A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems. Renaissance natural philosophers identified six simple machines which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today as mechanical advantage. Modern machines are complex systems that consist of structural elements, mechanisms and control components and include interfaces for convenient use. Examples include: a wide range of vehicles, such as trains, automobiles, boats and airplanes; appliances in the home and office, including computers, building air handling and water handling systems; as well as farm machinery, machine tools and factory automation systems and robots. The hand axe, made by chipping flint to form a wedge, in the hands of a human transforms force and movement of the tool into a transverse splitting forces and movement of the workpiece. The hand axe is the first example of a wedge, the oldest of the six classic simple machines, from which most machines are based. The second oldest simple machine was the inclined plane (ramp),[6] which has been used since prehistoric times to move heavy objects. The idea that a machine can be decomposed into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane. The modern approach to characterizing machines focusses on the components that allow movement, known as joints. A mechanical system manages power to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source and actuators that generate forces and movement, (ii) a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement, (iii) a controller with sensors that compare the output to a performance goal and then directs the actuator input, and (iv) an interface to an operator consisting of levers, switches, and displays. This can be seen in Watt's steam engine in which the power is provided by steam expanding to drive the piston.The walking beam, coupler and crank transform the linear movement of the piston into rotation of the output pulley.Finally, the pulley rotation drives the flyball governor which controls the valve for the steam input to the piston cylinder.

2. CONTENTS
Introduction
Classification Of Mechanisms
Degrees Of Freedom (Dof) / Mobility
Degrees Of Freedom/Mobility Of A Mechanism
Kutzbach Criterion
Grubler’s Criterion
Grashof’s Law

3. INTRODUCTION
Mechanism:
A combination of rigid or restraining bodies which are so shaped and
connected that they move upon each other with definite relative motion , is
known as a mechanism.
Machine:-
A machine is a mechanism or a combination of mechanisms which not only
imparts definite motions to the parts but also transmits and modifies the available
mechanical energy into some kind of useful energy.This useful energy may be in
the shape of some kind of desired work.

4. CLASSIFICATION OF MECHANISMS
When one of the links of a kinematic chain is fixed, the chain
is called Mechanism.
Types:
◊ Spatial - Links of a mechanism lie in
different planes
◊ Planar - All links lie in the same plane

5. CLASSIFICATION OF MECHANISMS
◊ Simple - 4 Links
◊ Compound - More than 4
◊ Complex -Ternary or Higher order
floating Links

6. DEGREES OF FREEDOM (DOF)/MOBILITY
It is the number of independent coordinates required to
describe the position of a body.
4 bar mechanism has 1 dof
as the angle turned by the
crankAD is fully describing
the position of the every
link of the mechanism.

7. DEGREES OF FREEDOM (DOF)/MOBILITY

8. DEGREES OF FREEDOM/MOBILITY OF A
MECHANISM
It is the number of inputs (number of independent coordinates)
required to describe the configuration or position of all the links of
themechanism, with respect to the fixedlink at any given instant.

9. KUTZBACH CRITERION
For mechanism having plane motion
DOF=3(L-1)-2J-H
Here:
 I= Numbur of Link
 J= Number of Lower Pair / Binery Joint
 H=Number of Higher Pair
NUMERICAL EXAMPLE:
Determine the DOF of the mechanism shown in the picture.
Here L= 5; J=2+2*(3-1)=6; H=0
DOF=3(5-1)-2*6-0=0
DOF=0; Means that the3 mechanism froms a structure.

10. KUTZBACH CRITERION
Determine the DOF for the links shown in the picture:
Note: at the intersection of 2, 3 and 4,
two lower pairs are to be considered
L =6 ; J =5+1(3-1)=7 ; H =0
DOF = 3(6-1)–2(7)–0= 1
i.e.- One input to any one link will result in definite motion of all the links.
L =4 ; J =3 ; H =1
DOF = 3(4-1)-(2*3)-1 = 2
DOF = 1
DOF = 2

11. GRUBLER’S CRITERION
Kutzbach Criterion n=3(L-1)-2J-H
Grubler’s criterion applies to mechanisms having 1 DOF,
Substituting n = 1 and h=0 in Kutzbatch equation, we canhave
Grubler’s equation.

12. GRASHOF’S LAW
According to Grashof ’s law for a four bar
mechanism, the sum of the shortest and longest link
lengths should not be greater than the sum of the
remaining two link lengths if there is to be continuous
relative motion between the two links.