Work is defined as the product of an applied force and the distance
through which the force acts. Work is measured in newton-meters, a metric
unit called a joule. Power is work per unit of time. Power is measured
in watts. One watt is 1 joule per second. Power is also measured in horsepower. One horsepower is 550 ft-lb/s.Energy is defined as the ability to do work.An object that is elevated
against gravity has a potential to do work. The object is said to have potential
energy, or energy of position. Moving objects have the ability to do
work on other objects because of their motion. The energy of motion is
called kinetic energy.
Work is usually done against inertia, fundamental forces, friction,
shape, or combinations of these. As a result, there is a gain of kinetic energy,
potential energy, an increased temperature, or any combination of these.
Energy comes in the forms of mechanical, chemical, radiant, electrical, or
nuclear. Potential energy can be converted to kinetic and kinetic can be
converted to potential. Any form of energy can be converted to any other
form. Most technological devices are energy-form converters that do work
for you. Energy flows into and out of the surroundings, but the amount
of energy is always constant. The law of conservation of energy states that
energy is never created or destroyed. Energy conversion always takes place
through heating or working.
The basic energy sources today are the chemical fossil fuels (petroleum,
natural gas, and coal), nuclear energy, and hydropower. Petroleum
and natural gas were formed from organic material of plankton, tiny freefloating
plants and animals. A barrel of petroleum is 42 U.S. gallons, but
such a container does not actually exist. Coal formed from plants that
were protected from consumption by falling into a swamp. The decayed
plant material, peat, was changed into the various ranks of coal by pressure
and heating over some period of time. Coal is a dirty fuel that contains
impurities and sulfur. Controlling air pollution from burning coal
is costly. Moving water and nuclear energy are used for the generation of
electricity. An alternative source of energy is one that is different from the
typical sources used today. Alternative sources could be solar, geothermal,
hydrogen, or fusion.
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