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Glossary

# Glossary

basal metabolic rate
the total energy conversion rate of a person at rest
chemical energy
the energy in a substance stored in the bonds between atoms and molecules that can be released in a chemical reaction
conservation of mechanical energy
the rule that the sum of the kinetic energies and potential energies remains constant if only conservative forces act on and within a system
conservative force
a force that does the same work for any given initial and final configuration, regardless of the path followed
efficiency
a measure of the effectiveness of the input of energy to do work; useful energy or work divided by the total input of energy
electrical energy
the energy carried by a flow of charge
energy
the ability to do work
fossil fuels
oil, natural gas, and coal
friction
the force between surfaces that opposes one sliding on the other; friction changes mechanical energy into thermal energy
gravitational potential energy
the energy an object has due to its position in a gravitational field
horsepower
an older non-SI unit of power, with $1 hp = 746 W1 hp = 746 W$
joule
SI unit of work and energy, equal to one newton-meter
kilowatt-hour
$(kW⋅h)(kW⋅h) size 12{ $$"kW" cdot h$$ } {}$ unit used primarily for electrical energy provided by electric utility companies
kinetic energy
the energy an object has by reason of its motion, equal to $12mv212mv2 size 12{ { {1} over {2} } ital "mv" rSup { size 8{2} } } {}$ for the translational (i.e., nonrotational) motion of an object of mass $mm size 12{m} {}$ moving at speed $vv size 12{v} {}$
law of conservation of energy
the general law that total energy is constant in any process; energy may change in form or be transferred from one system to another, but the total remains the same
mechanical energy
the sum of kinetic energy and potential energy
metabolic rate
the rate at which the body uses food energy to sustain life and do different activities
net work
work done by the net force, or vector sum of all the forces, acting on an object
nonconservative force
a force whose work depends on the path followed between the given initial and final configurations
nuclear energy
energy released by changes within atomic nuclei, such as the fusion of two light nuclei or the fission of a heavy nucleus
potential energy
energy due to position, shape, or configuration
potential energy of a spring
the stored energy of a spring as a function of its displacement; when Hooke’s law applies, it is given by the expression $12kx212kx2 size 12{ { {1} over {2} } ital "kx" rSup { size 8{2} } } {}$ where $xx size 12{x} {}$ is the distance the spring is compressed or extended and $kk size 12{k} {}$, is the spring constant
power
the rate at which work is done
(W) SI unit of power, with $1 W = 1 J/s1 W = 1 J/s$