mechanical energy

Definition:

Scientifically, mechanical energy is defined by
the formula:

E = U + K

Here, U represents potential energy (height ×
mass × 9.8 m/s^2) and K (1/2 × mass ×
velocity^2) represents kinetic energy. As the
formula denotes, mechanical energy is the total
output of energy acquired by adding the
potential energy and the kinetic energy
involved in a particular case. In other words,
the mechanical energy of an object is
determined by its motion and position. After
considering this, we can safely say that gravity
is the only outside force significant enough to
be concerned when it comes to mechanical
systems.
Mechanical energy should not be confused
with other forms of energy like electromagnetic
energy, nuclear energy, chemical energy and
such, as they all have different origins.
Significant examples of objects that exhibit
instances of continuous mechanical energy are
objects that are in constant motion; such as
satellites and pendulums. However, almost
every movement or set of movements involves
mechanical energy, whether it is a soccer ball
being kicked or a leaf falling off a branch. Note
that mechanical energy is also stored in
objects that work on the principle of tension as
we can see in the case of stretchable rubber
bands. Each time they are stretched and let go
of, an insurgence and decline of mechanical
energy can be observed.
Mechanical energy can also be and often is
defined by physics as the ability or capability to
do work. It empowers an object to displace
another object through the application of force
and therefore anything which is capable of
causing some sort of displacement can be
acknowledged to possess mechanical energy.
It is measured in terms of joules, as is the
case with all other forms of energy as well.
The hammer is a fine example of a tool which
operates on the principle of mechanical energy
to do work. The hammer itself possesses
potential energy and when it is swung back
and forth to strike a nail, it also gains kinetic
energy. The combination of the two forms of
energy gets converted into mechanical energy
and with the help of that energy; the nail is
displaced/put further into the surface. The
amount of displacement of the nail from its
prior position, each time the hammer hits it is
the amount of work being done with each
strike.
Conversion of mechanical energy
Energy cannot be created or destroyed in an
isolated environment as we all know, but it can
be converted from one form to the other;
known as internal conversion. The most
significant technological inventions in the field
of conversion of energy include the electric
motor, the generator, the steam engine, the
turbine and the internal combustion engine
among others.
The various forms of conversion associated
with mechanical energy are what make
mechanical energy evermore useful to us. An
example of helpful conversion can be cited if
one observes the energy conversion which
takes place inside a car motor. The gas which
we fill our cars with, contains chemical energy
in it; however, when the fuel is burned by the
motor to make the vehicle move, that same
chemical energy is turned into useful
mechanical energy.
Sources of useful mechanical
energy
It should be noted that science is of the opinion
(also backed by logic) that mechanical energy
is the first form of energy that was ever
utilized by human beings effectively, back in
the prehistoric ages. It was the use of brute
force and through the employment of beasts
that men attained useful mechanical energy
back in those days, however, let us discuss
some of the more modern sources of this
energy.
1. Hydroelectric plants –- Hydroelectric plants
take advantage of the fact that water can be
utilized to produce mechanical energy from,
both while it is at rest and when it is in motion.
The principle goal of these plants however, is
to convert this mechanical energy into useable
and storable electric energy or
hydroelectricity.
The most important and basic part of any
hydroelectric plant is the dam, an elevated
structure built across a water body (river, lake)
to make use of the stagnant as well as flowing
water when required. Other parts of a dam that
function in various ways to convert and store
energy are reservoirs, penstocks, pipelines,
transformers and generators.
Perhaps a more direct use of mechanical
energy attained through employing hydropower
can be observed if we look at models of
watermills for milling grain that were used
thousands of years ago by ancient civilizations.
It did not involve any conversion of mechanical
energy into other forms of energy, but focused
purely on the mechanical energy present in
moving water.
2. Tidal plants –- Actually, tidal power plants
are also a kind of hydroelectric power plants
but they differ in certain ways. Tidal power
plants are built on oceans and these plants
take advantage of both the thermal energy of
the sun as well as the mechanical energy
present in crashing tides and waves. Water
mills, barrages, buoys and tidal generators are
common components used in conversion of
the mechanical energy into electrical energy at
these plants and in many ways they resemble
normal hydroelectricity plants, though are not
the same.
The advantages of using tides as a source of
energy is the fact that they are much more
predictable that the sun or the wind; the other
two sources of alternate energy. However,
tidal plants are not yet widely implemented due
to the high costs associated with such
structures and also due to a lack of spots fit
for sufficient yielding. This is nonetheless, a
possible source of alternate energy in the
future.
3. Windmills or wind power plants -– Wind, in
addition to water is another natural element
that is used by us as a source of mechanical
energy (and converted into electrical energy).
The basic structure of a wind power plant
consists of a windmill (which has either the
vertical or the horizontal turbine), but in order
to convert the mechanical energy into
electrical energy, motors and electrical
generators are required of course. Principle of
a wind power plant is to harness the kinetic
energy found in wind and combine it with the
potential energy of the turbines in order to
produce mechanical energy; which in turn, can
be converted into electricity by the motors and
generators.
One should note that although generation of
electrical energy is the ultimate goal, the
mechanical energy is also put into more direct
use. Windmills are used as means for cutting
wood, pumping water and grinding grains still
today due to the efficiency of the process.
However, a wind mill is particularly suited for
areas that have constantly high wind speed (5
to 15.5 to be precise) most of the time. The
term CONSTANT is more important here as
uniformity is the key element in maintaining a
working windmill.
Conservation of mechanical energy
The law of mechanical energy conservation
states that the total mechanical energy of a
system that is not hindered by resistive forces
such as friction or air resistance remains
unchanged and thus constant. In order to
measure the exact mechanical energy of a
system, we need to calculate its speed (kinetic
energy) and its height above the reference
point (potential energy).