Physics
There are different approaches to flight. If an object has a lower density than air, then it is buoyant and is able to float in the air without using energy. A heavier than air craft, known as an aerodyne, includes flighted animals and insects, fixed-wing aircraft and rotorcraft. Because the craft is heavier than air, it must generate lift to overcome its weight. The wind resistance caused by the craft moving through the air is called drag and is overcome by propulsive thrust except in the case of gliding.
Some vehicles also use thrust for flight, for example rockets and Harrier Jump Jets.
Finally, momentum dominates the flight of ballistic flying objects.
Read more about this topic: Flight
Famous quotes containing the word physics:
“Although philosophers generally believe in laws and deny causes, explanatory practice in physics is just the reverse.”
—Nancy Cartwright (b. 1945)
“The pace of science forces the pace of technique. Theoretical physics forces atomic energy on us; the successful production of the fission bomb forces upon us the manufacture of the hydrogen bomb. We do not choose our problems, we do not choose our products; we are pushed, we are forced—by what? By a system which has no purpose and goal transcending it, and which makes man its appendix.”
—Erich Fromm (1900–1980)
“The fundamental laws of physics do not describe true facts about reality. Rendered as descriptions of facts, they are false; amended to be true, they lose their explanatory force.”
—Nancy Cartwright (b. 1945)