The subject Theory of Machines may be defined as
that branch of Engineering-science, which deals with the study
of relative motion between the various parts of a machine,
and forces which act on them. The knowledge of this subject
is very essential for an engineer in designing the various parts
of a machine.A machine is a device which receives energy in some
available form and utilises it to do some particular type of work.
the following four branches :
1. Kinematics. It is that branch of Theory of
Machines which deals with the relative motion between the
various parts of the machines.
2. Dynamics. It is that branch of Theory of Machines
which deals with the forces and their effects, while acting
upon the machine parts in motion.
3. Kinetics. It is that branch of Theory of Machines
which deals with the inertia forces which arise from the combined
effect of the mass and motion of the machine parts.
4. Statics. It is that branch of Theory of Machines
which deals with the forces and their effects while the machine
parts are at rest. The mass of the parts is assumed to be
negligible.
fundamental quantities :
1. Length (L or l ),
2. Mass (M or m), and
3. Time (t).
Derived Units
Some units are expressed in terms of fundamental units known as derived units, e.g., the units
of area, velocity, acceleration, pressure, etc.
Systems of Units
There are only four systems of units, which are commonly used and universally recognised.
These are known as :
1. C.G.S. units,
2. F.P.S. units,
3. M.K.S. units, and
4. S.I. units.
second respectively. The C.G.S. units are known as absolute units or physicist's units.
respectively.
systematically constituted system of fundamental and derived units for international use. This system
is now being used in many countries. In India, the standards of Weights and Measures Act, 1956 (vide
which we switched over to M.K.S. units) has been revised to recognise all the S.I. units in industry
and commerce.
* It is known as General Conference of Weights and Measures (G.C.W.M.). It is an international organisation,
of which most of the advanced and developing countries (including India) are members. The conference
has been entrusted with the task of prescribing definitions for various units of weights and measures, which
are the very basic of science and technology today.
that branch of Engineering-science, which deals with the study
of relative motion between the various parts of a machine,
and forces which act on them. The knowledge of this subject
is very essential for an engineer in designing the various parts
of a machine.A machine is a device which receives energy in some
available form and utilises it to do some particular type of work.
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| Theory of Machine |
Sub-divisions of Theory of Machines
The Theory of Machines may be sub-divided intothe following four branches :
1. Kinematics. It is that branch of Theory of
Machines which deals with the relative motion between the
various parts of the machines.
2. Dynamics. It is that branch of Theory of Machines
which deals with the forces and their effects, while acting
upon the machine parts in motion.
3. Kinetics. It is that branch of Theory of Machines
which deals with the inertia forces which arise from the combined
effect of the mass and motion of the machine parts.
4. Statics. It is that branch of Theory of Machines
which deals with the forces and their effects while the machine
parts are at rest. The mass of the parts is assumed to be
negligible.
Fundamental Units
The measurement of physical quantities is one of the most important operations in engineering. Every quantity is measured in terms of some arbitrary, but internationally accepted units, called fundamental units. All physical quantities, met within this subject, are expressed in terms of the following threefundamental quantities :
1. Length (L or l ),
2. Mass (M or m), and
3. Time (t).
Derived Units
Some units are expressed in terms of fundamental units known as derived units, e.g., the units
of area, velocity, acceleration, pressure, etc.
Systems of Units
There are only four systems of units, which are commonly used and universally recognised.
These are known as :
1. C.G.S. units,
2. F.P.S. units,
3. M.K.S. units, and
4. S.I. units.
C.G.S. Units
In this system, the fundamental units of length, mass and time are centimetre, gram andsecond respectively. The C.G.S. units are known as absolute units or physicist's units.
F.P.S. Units
In this system, the fundamental units of length, mass and time are foot, pound and secondrespectively.
M.K.S. Units
In this system, the fundamental units of length, mass and time are metre, kilogram and secondrespectively. The M.K.S. units are known as gravitational units or engineer's units.International System of Units (S.I. Units)
The 11th general conference* of weights and measures have recommended a unified andsystematically constituted system of fundamental and derived units for international use. This system
is now being used in many countries. In India, the standards of Weights and Measures Act, 1956 (vide
which we switched over to M.K.S. units) has been revised to recognise all the S.I. units in industry
and commerce.
* It is known as General Conference of Weights and Measures (G.C.W.M.). It is an international organisation,
of which most of the advanced and developing countries (including India) are members. The conference
has been entrusted with the task of prescribing definitions for various units of weights and measures, which
are the very basic of science and technology today.
