A simple machine is
an elementary device that has a specific movement (often called a mechanism), which can be combined with other
devices and movements to form a machine.
Thus simple machines are considered to be the "building blocks" of
more complicated machines. This
analytical view of machines as
decomposable into simple machines first arose in the Renaissance as a neoclassical amplification of ancient Greeks texts on technology, and
is still a central part of engineering in
today's age of applied science. For
example, wheels, levers, and pulleys are all used in the mechanism of a bicycle. Between the simple machines and
complex assemblies, several intermediate classes can be defined, which may be
termed "compound machines" or "machine elements". The
mechanical advantage of a compound machine is simply the product of the
mechanical advantages of the simple machines of which it is composed.
Classifications
of Simple Machines
Lever - is a machine consisting
of a beam or rigid rod pivoted at a fixed hinge,
or fulcrum. The ideal lever does not dissipate or store energy, which
means there is no friction in the hinge or bending in the beam. In this case, the
power into the lever equals the power out, and the ratio of output to input
force is given by the ratio of the distances from the fulcrum to the points of
application of these forces. This is known as the law of the lever.
Classes of Levers
Class 1: Fulcrum in the middle: the effort is applied on one side of the
fulcrum and the resistance on the other side.
Examples:
Class 2: Resistance in the middle: the effort is applied on one side of
the resistance and the fulcrum is located on the other side.
Examples:
Class 3: Effort in the middle: the resistance is on one side of the
effort and the fulcrum is located on the other side.
Examples:
Wheel and Axle - is one of six simple machines identified by
Renaissance scientists drawing from Greek texts on technology. The wheel
and axle is generally considered to be a wheel attached to
an axle so that these two parts rotate together in which a force is
transferred from one to the other. In this configuration a hinge,
or bearing, supports the rotation of the axle.
Examples:
Pulley - is a wheel on an axle that is designed to
support movement of a cable or belt along its circumference. Pulleys are
used in a variety of ways to lift loads, apply forces, and to transmit power.
The drive element of a pulley system can be a rope, cable, belt, or chain that
runs over the pulley inside the groove.
Examples:
Inclined plane -is a flat supporting surface tilted at an angle, with one end
higher than the other, used as an aid for raising or lowering a load. The
inclined plane is one of the six classical simple machines defined by
Renaissance scientists. Inclined planes are widely used to move heavy loads
over vertical obstacles.
Examples:
Wedge - is a triangular shaped tool, a compound and
portable inclined plane of a wedge is given by the ratio of the
length of its slope to its width. Although a short wedge with a
wide angle may do a job faster, it requires more force than a long wedge with a
narrow angle.
Examples:
Screw - is a type
of fastener characterized by a helical ridge, known as
an external thread or
just thread, wrapped around a cylinder. A screw will always have a head, which is a specially formed section on one end of the
screw that allows it to be turned, or driven. The head is usually
larger than the body of the screw, which keeps the screw from being driven
deeper than the length of the screw and to provide a bearing surface.
Examples:
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