Energy, Work, and Power
LAW OF CONSERVATION OF ENERGY
Rev. 0
Page 7
CP05
Conservation of Energy Summary
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Energy cannot be created or destroyed, only altered in form.
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Simplified energy balance:
KE + PE + E
= KE + PE + E
1
1
added
2
2
removed
To further describe each of the components of the above equation, each component can be
broken down as follows:
Energy
= KE + PE
initial
1
1
Energy
= Work done on and heat added to the system
added
Energy
= Work done by and heat removed from the system
removed
Energy
= KE + PE
final
2
2
The resulting energy balance is provided in Equation 55.
KE + PE + E
 E
= KE + PE
(55)
1
1
added
removed
2
2
Neglecting any heat removed or added to a system, we can replace E
and E
in
added
removed
Equation 55 with their associated work terms to obtain Equation 56.
KE + PE + W = KE + PE + W
(56)
1
1
on
2
2
by
The final energy balance is called a "simplified energy balance." Any energy balance is a
statement of the Law of Conservation of Energy. In this simplified form, the balance applies
only to mechanical problems, since we neglected heat. However, more specific energy balances
that include heat will be discussed in other Fundamental Manuals. For example, specific energy
balances for flow systems will be discussed in the Heat Transfer, Fluid Flow, and
Thermodynamics modules.
Summary
The law of conservation of energy is summarized below.

