Sir Isaac Newton first presented his three laws
of motion in the "Principia Mathematica Philosophiae Naturalis"
in 1686. His third law states that for every action (force) in nature
there is an equal and opposite reaction. In other words, if object A
exerts a force on object B, then object B also exerts an equal and
opposite force on object A. Notice that the forces are exerted on
Powered aircraft are an excellent example of the application of the
third law of motion.
Both the lift and thrust of the
Wright 1903 Flyer
can be explained by the third law.
Considering the generation of lift
by the wing of the aircraft, the air moving past the wing is deflected downward
by the shape and the motion of the wing. The wing exerts a force, or action, on
the air and in re-action the wing is pushed upward by the air.
The 1903 flyer used twin
attached to a small motor to generate
The propellers accelerate a large mass of air by a small amount
across the propeller disk. The propellers exert a force (action) on the mass
of air and push the air to the rear of the aircraft. In re-action, the
propellers are pushed forward by the air. Since the propellers are attached
to the aircraft, the entire aircraft is pushed forward by the action of the propellers.
- Re-Living the Wright Way
- Beginner's Guide to Aeronautics
- NASA Home Page