Question

Explain how an airplane gets into air. Being sure to use the terms " lift" and "internal pressure ".

Answer 1

Flight requires two things: thrust and lift. Thrust is the forward motion provided by a propeller or jet engine. (A propeller, by the way, uses the same principles discussed below to create lift, but it uses that lift to move the plane forward instead of up.)

Lift :

Lift is a lot trickier than thrust. An airplane wing has a special shape, called an airfoil, that bulges more on top than on the bottom. That shape aids in flight, but is not the key.

When air meets the wing, it splits into two streams, top and bottom. You'll often hear that the two streams meet up again in the back, as depicted here, because the air passing over the top has to travel farther than the air going underneath, so it is forced to move faster. But in fact, parcels of air do not join back up in any uniform manner.

Faster-moving air has less pressure (this is often called the Bernoulli principle). So the area above the wing is often said to have less pressure than the area below the wing, creating lift, internal pressure is changed.

Again, the reality is more complex, and Newton's laws are typically preferred over the Bernoulli principle to explain lift. The Newtonian idea is this: Air flowing over the wing is ultimately deflected downward by the angle of the wing, and Newton said there has to be an equal and opposite reaction, so the wing is forced upward.