### Science of Flight

Scientist Daniel Bernoulli discovered that the amount of energy in any system remains the same. Therefore, if one part of the system increases than another portion of the system must decrease, so that the system remains constant.

There are 4 main forces that act upon an aircraft at any time:

1. Lift occurs because the distance over the top of the wing is further then the distance under the wing creating two different zones of pressure. The wind going over the top of the wing goes faster causing a low pressure and the wind going under the wing is slower causing a  high pressure. The high pressure wants to get to the side of the wing with the low pressure. This creates lift which lets the plane fly.

2. Drag is the force that slows an object moving through the air down. The smaller and more streamlined the object the less  drag effects the aircraft allowing the aircraft to go faster. The larger the object the slower it will go because more wind is hitting the surface of the aircraft or object. Drag is usually a disadvantage either in slowing the aircraft down or reducing the distance it can fly. Drag also effects cars, trucks and any other objects moving through the air.

3. Thrust is the force that pushes the plane forward. This propulsion is usually generated  by the engines. The thrust is the force that opposes drag.  Without thrust to move the plane forward, getting the wind to flow over the wing, lift would not be generated.

4. Gravity is the force that pulls down on the plane at all times even while the plane is in flight. Luckily  lift overcomes this force.  A dangerous situation can occur if gravity overcomes lift in an uncontrolled manor.

Swept Wings:

As aircraft get closer to the sound barrier, shock waves build up in front of the aircraft and along the wings. Designers discovered that if they swept the wing back at an angle, it would delay the shock waves from building up. If the shock waves are reduced, it lessons the drag on the aircraft allowing it to go faster or fly further. However, swept wings do not provide as much lift as straight wings at slow speeds. Therefore, landing speed is increased. Designers must decide what type of aircraft they want to match the wing design and whether to sweep the wings or not.

Weather:

Weather can affect flight in more than one way. Cold weather makes flying easier because the air is denser then on a normal day. Dense air provides more lift then warm air. In warm weather it makes flying a little harder because the warm air provides less lift. Aircraft that have to takeoff in hot and high climates must have longer runways or takeoff with less weight in order to get airborne. Some weather hazards to flying are hail, ice, turbulence, storms and wind shear.