| A | B |
|---|
| drag | the resistance encountered by all aircraft as they move through the air |
| elevators | the flaps located on the horizontal stabilizer of the tail assembly that control the pitch of the airplane |
| envelope | on a hot-air balloon, the large, usually globe-shaped nylon bag filled with heated air |
| fuselage | the tube-shaped body of an aircraft that houses the passengers and cargo |
| gravity | as experienced on Earth, the gravitational force between the Earth and objects that are on or near the Earth. Gravity pulls all objects down, toward the center of the Earth |
| hub | the center point to which propeller or rotor blades are attached |
| jet engine | a type of engine that produces thrust by the explosive movement of gases through the engine unit |
| lift | the force that pushed an object up, against the force of gravity |
| molecule | a tiny particle of matter; the smallest part of a compound having all the properties of that compound |
