KE
mv2
2gc
10 lbm
2
8 ft
sec
2
lbf sec2
32.17 lbm ft
KE
(5 lbm)
64 ft2
sec2
lbf sec2
32.17 lbm ft
Energy, Work, and Power
ENERGY AND WORK
Rev. 0
Page 3
CP-05
where:
KE
=
kinetic energy in ft-lbf
m
=
mass in lbm
v
=
velocity in ft/sec
g
=
(32.17 lbm-ft)/(lbf-sec )
c
2
Example:
What is the kinetic energy of a 10 lbm object that has a velocity of 8 ft/sec?
Answer:
KE = 9.95 ft-lbf
The kinetic energy of an object represents the amount of energy required to increase the
velocity of the object from rest (v = 0) to its final velocity, or the work it can do as it pushes
against something in slowing down (waterwheel or turbine, for example.)
Thermal Energy
Thermal energy is that energy related to temperature (the higher the temperature, the greater
the molecular movement, and the greater the energy). If one object has more thermal energy
than an adjacent substance, the substance at the higher temperature will transfer thermal energy
(at a molecular level) to the other substance. Note that the energy is moving from one place
to another (it is in motion) and is referred to as transient energy or, more commonly in the case
of thermal energy, heat.
The only stored energy in a solid material is internal energy. Internal energy is the energy
stored in a substance because of the motion and position of the particles of the substance. Heat
and internal energy will be covered in the Fundamentals Manual on Heat Transfer, Fluid Flow,
and Thermodynamics.
Mechanical Energy
Mechanical energy is energy related to motion or position. Transient mechanical energy is
commonly referred to as work. Stored mechanical energy exists in one of two forms: kinetic
or potential. Kinetic and potential energy can be found in both fluids and solid objects.
