Environmental Engineering Reference
In-Depth Information
There are two basic forms of energy:
kinetic energy
and
potential energy
. Kinetic
energy is energy at work or in motion—that is, moving energy; for example, a car
in motion or a rotating shaft has kinetic energy. In billiards, a player gives the cue
ball kinetic energy when she strikes the ball with the cue. As the ball rolls, it exerts
kinetic energy. When the ball comes into contact with another ball, it transmits its
kinetic energy, allowing the next ball to be accelerated. Potential energy is stored
energy, such as the energy stored in a coiled or stretched spring or an object stationed
above a table. A roller coaster has the greatest potential energy when it is stopped at
the top of a long drop. Another example of potential energy is when a can of carbon-
ated soda remains unopened. The can is pressurized with gas that is not in motion
but that has potential energy. When the can is opened, the gas is released and the
potential energy is converted to kinetic energy.
According to the law of conservation of energy, energy cannot be made or
destroyed but can be made to change forms. Moreover, when energy changes from
one form to another, the amount of energy stays the same. Let's consider an exam-
ple of the law of conservation of energy: The initial energy of something is mea-
sured. The energy then changes from potential (stored) energy to kinetic (moving)
and back again. After that, the energy is measured again. The energy measured at
the start is the same as that measured at the end; it will always be the same. One
caveat to this explanation is that we now know that matter can be made into energy
through processes such as nuclear fission and nuclear fusion. The law of conserva-
tion of energy has therefore been modified or amplified to become the law of con-
servation of matter and energy.
TYPES OF ENERGY
The many types of energy include the following:
•
Kinetic (motion) energy
•
Water energy
•
Potential (at rest) energy
•
Elastic energy
•
Nuclear energy
•
Chemical energy
•
Sound energy
•
Internal energy
•
Heat/thermal energy
•
Light (radiant) energy
•
Electric energy
Energy sources can also be categorized as renewable or nonrenewable. When we
use electricity in our home, the electrical power was probably generated by burn-
ing coal, by a nuclear reaction, or by a hydroelectric plant at a dam (EIA, 2009);
therefore, coal, nuclear, and hydropower are called
energy sources
. When we fill up
a gas tank, the source might be petroleum or ethanol made by growing and process-
ing corn.
