In the vertical axis, gravity pulls the craft towards the Earth with a force equal to its weight.
When the craft is not gaining or losing height, the lift force produced by the wing equals the weight.
An aircraft flies because the forces due to air resistance are not equal on the top and bottom of a wing, creating lift.
The aircraft's wings are shaped in just the right way to create a difference in air pressure.
Because there is air resistance, there is a resistance to this movement forward, called drag.
Drag is always in the opposite direction to the thrust.At a certain speed, the air resistance is equal to the force of gravity pulling him through the air. If there is no net force, Newton's Second Law of Motion, F = m.a, dictates that he is experiencing no acceleration - therefore his velocity is constant.The velocity at which a falling object is no longer accelerating due to air resistance is known as terminal velocity.This is the first principle of air resistance: an object will have resistance proportional to its surface area and speed as it moves through a gas or liquid.This is because the object is trying to push through more air molecules as it moves.Although air molecules are very small and light, there are a lot of them - enough to cause a piece of paper or feather to slow right down as it falls.To test if it really is the air slowing the objects down, we need to drop them where there is no air.A few months ago, skydiver Felix Baumgartner jumped from 39 kilometers, and hit Mach 1 around 30 kilometers.This was enough to heat the air by a few degrees, but the air was so far below freezing that it didn’t make a difference.From what height would you need to drop a steak for it to be cooked when it hit the ground?—Alex Lahey I hope you like your steaks Pittsburgh Rare.