Net Forces on
an Airplane
The external forces on an airplane in flight
heading westward are as follows:
gravity, thrust, drag, and lift.
They are not all along the same
line.
The gravity represents the
weight of the aircraft.
The drag
is caused by air resistance on the aircraft.
The
thrust is due to the engine and propeller.
How does lift work?
According to Daniel Bernoulli who
presented his fact in 1738.
Fast moving
fluids (such as air), exhibit less force than slow moving
fluids.
where p is the pressure,
r
is the density, and v
is the velocity.
A large velocity v
results in a small pressure p, and conversely a small
velocity v results in a large pressure p.
If we produce a surface such that
air takes longer to travel over the top than the bottom, the
surface will produce a net upward force. Such a surface is
called an
airfoil and the net force is called
lift.
(Dr.
Bob Gardner, East Tennessee State University)
