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Energy
Energy defined as the capacity to do work, may exist in potential, kinetic, thermal, electrical,
chemical, nuclear, or other various forms. There are, moreover, heat and work-i.e. energy in the
process of transfer from one body to another. After it has been transferred, energy is always
designated according to it nature. Heat transferred may become thermal energy, while work done may
manifest itself in the form of mechanical energy.
All forms of energy are associated with motion. For example, a given body has kinetic energy
if it is in motion. A tensioned developed such as a bow or spring, though at rest, has the potential for creating
motion; it contains potential energy because of its configuration. Similarly, nuclear energy is potential energy
because it results the configuration of subatomic particles in the nucleus of an atom.
All of the energy in biological processes on earth comes from thermonuclear reactions taking place in
the sun, which gives rise to ultraviolet, visible, and infrared radiation that, is then emitted from the solar
surface. A fraction of the visible radiation falling on the earth’s surface is absorbed by a group of living
organisms, the photoautototrophs.
Kinetic Energy is the energy of motion. The magnitude of Kinetic energy, , of an object
depends on its mass, m, and speed, :  = ½ mv²
Example: A baseball traveling at the speed of 30 miles per hour has a greater kinetic energy than a
baseball traveling at 20 miles per hour.
At a given speed, the kinetic energy increases with increasing mass. Thus, a truck traveling at 70 mph has
greater kinetic energy than a small compact car traveling at the same speed, because of the greater mass of
the former.
Potential Energy is stored energy that results from the attraction and results from the attaractions and repulsions an object experiences in relation to other objects.
Example: A bicyclist traveling down a hill will have greater potential energy at the top because of
the gravity at the top of the hill with the increasing speed.
Unit Used
The SI unit for energy is joule, which is pronounced “jool” A joule is not a large amount
of energy and we often uses kilojoules (kJ) and discussing energies that are associated with
chemical reactions. 1 J = 1 kg-m²/s². The SI unit was named in honor of James Prescott Joule for
experiments with work and heat.
Eĸ= ½ mv²=
½(2kg) (1 m/s) ² =
1 Kg-m²/s² =
1J
References
Brown, T., Bursten, B., LeMay. E., Chemistry: The Central Science 8th Ed., Prentice Hall
Publishing, 2000, p.146-7.
“Energy” Encyclopedia Britannica
http://search.eb.com/eb/article/
“Energy” Grolier Encyclopedia
http://ea.grolier.com/cgi-bin/build-page/