Lift | Drag | Thrust | Gravity | Bernoulli's Principle | The Venturi Effect | Newton's Law's | The Truth about Bernoulli
L i f t
Firstly, we need to understand something about air pressure. Air pressure is caused by the collisions of air particles with one another. Air pressure in flowing air is less than that in stationery air. This is because in flowing air, particles are moving in the same direction. This means that there are less collisions and therefore lower pressure. In standing air, the particles are constantly moving and colliding. This means more collisions and therefor a higher pressure. This is called Bernoulli’s law.
(Above) Representation of moving and stationery air particles. Notice how more collisions would occur in the first image because the random movements of the particles. In the second image, all the particles move in one common direction. This results in less collisions and therefore less pressure.
A wing has a shape called an airfoil and the top surface is longer than the bottom surface because the top is curved and the bottom is flatter.
If the wings are mounted with the leading edge tilted slightly upwards, the air will strike the lower surface more directly. The tilt is called the Angle of Attack (AOA). If it is a positive AOA, the wing is tilted upwards and there is a greater pressure difference between the top and the bottom surface. Therefore the lift increases. If it’s a negative AOA, the wing is tilted downwards and the pressure difference is less. Therefore the lift decreases.
Other factors determining lift are:
Currently, Lockhead Martin is working on an aircraft capable of carrying 1 million pounds of cargo! It would have to generate massive amounts of lift in order to achieve this. Apparently, the designers of the craft plan to use helium and tilt rotors (vertical take-off) to create this massive amount of lift. This also means that the vessel will be able to hover in one place making it the most useful and the biggest utility craft ever!
Drag is caused by friction between the aeroplane and the particles in the air. It opposes thrust and will decrease the speed of an aeroplane.
(Above) An illustration of how the shape of an object affects the amount of drag experienced
These days aeroplanes and boats are designed to have the least amount of drag possible so that greater speeds can be achieved.
Designers of high-speed aircraft must also take into account other aerodynamic concepts such as the boundary layer. This is the layer of air nearest the skin of the aeroplane where the effects of the turbulence and drag caused by air resistance are the strongest. It is obviously better to keep turbulence to a minimum, so most aeroplane are now designed to keep this layer of air as undesturbed as possible, hence the term streamlining.
Thrust is produced by the propeller or jet engine of an aeroplane and is essential in helping to produce lift. The forward motion of the aeroplane will continue as long as the thrust is greater than the drag.
(Above) A simple illustration of how a turbofan engine produces thrust
The propeller is angled slightly and this angle allows it to push through the air particles rather than just turning. A jet engine sucks air in through the intakes and pushes is out through the engine, thus creating thrust.
Firstly we need to know the difference between Mass and Weight.
Mass is the amount of matter an object contains. Weight is the force gravity exerts on the object.
The pull of gravity is determined by the objects mass. An airplanes mass will include the frame, engines, fuel, oil, pilot, crew, passengers, cargo, equipment etc.
" Once you have flown, you will walk the earth with your eyes turned
Leonado da Vinci