Newton's Second Law of Motion. The second law states that an
imbalance of forces on a body produces or tends to produce an
acceleration in the direction of the greater force, and the
acceleration is directly proportional to the force and inversely
proportional to the mass of the body.
Newton's Third Law of Motion. The third law states that for
every action there is an equal and opposite reaction, and the two are
directed along the same straight line.
Bernoulli's Principle. This principle states that if the
velocity of a gas or liquid is increased its pressure will decrease.
The opposite is also true. If the velocity of a gas or liquid is
decreased its pressure will increase. This fact relates directly to
the law of conservation of energy.
Einstein's Law of Conservation of Energy. This law states
that the amount of energy in the universe remains constant. It is
not possible to create or destroy energy; however, it may be
transformed.
Boyle's Law. This law states that if the temperature of a
confined gas is not changed, the pressure will increase in direct
relationship to a decrease in volume. The opposite is also true
the pressure will decrease as the volume is increased. A simple
demonstration of how this works may be made with a toy balloon. If
you squeeze the balloon, its volume is reduced, and the pressure of
air inside the balloon is increased. If you squeeze hard enough, the
pressure will burst the balloon.
Charles' Law. This law states that if a gas under constant
pressure is so confined that it may expand, an increase in the
temperature will cause an increase in volume. If you hold the
inflated balloon over a stove, the increase in temperature will cause
the air to expand and, if the heat is sufficiently great, the balloon
will burst. Thus, the heat of combustion expands the air available
within the combustion chamber of a gas turbine engine.
Pressure and Velocity. Air is normally thought of in relation
to its temperature, pressure, and volume. Within a gas turbine
engine the air is put into motion so now another factor must be
considered, velocity. Consider a constant airflow through a duct.
As long as the duct crosssectional area remains unchanged, air will
continue to flow at the same rate (disregard frictional loss). If
the crosssectional area of the duct should become smaller (convergent
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