air resistance

In flight, the forces on an aeroplane are lift, weight, drag, and thrust. The lift is generated by the air flow over the wings, which have the shape of an aerofoil. The engine provides the thrust. The drag results from the resistance of the air to the aeroplane's passage through it. Various moveable flaps on the wings and tail allow the aeroplane to be controlled. The rudder is moved to turn the aeroplane. The elevators allow the craft to climb or dive. The ailerons are used to bank the aeroplane while turning. The flaps, slats, and spoilers are used to reduce lift and speed during landing.

Force tending to oppose the motion of a body as it moves through air. It is a form of friction. An object falling through the air experiences a force due to air particles opposing its motion, which has the effect of slowing down the object. Air resistance is greater for objects moving faster and with greater areas.

As an example, a parachutist jumping from an aircraft will initially accelerate due to the force of gravity. As the speed increases the air resistance slows down the parachutist, reducing the acceleration. Eventually the air resistance balances the force of gravity, at which point the parachutist falls at a constant velocity called the terminal velocity. As the parachute opens, the large area of the parachute experiences greater air resistance than the parachutist, and slows the descent.