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Why is the drag on an airplane proportional to the square of its airspeed?
Wiki User
∙ 16y ago
Terms To Know.
Free Stream Velocity: The velocity with which the air hits the airplane or the airplane hits the air. Denoted by Vinfinity . [Assume V in this case!]
Dynamic Pressure: Its is defined as the pressure that the air has by the virtue of its motion. Denoted by Pinfinity [ Assume P in this case]
Pinfinity= 0.5*d*V2
Coefficient Of Drag: It is a unit-less number that determines the lift on a body. Denoted by Cd.
Surface Area: It is the planform Area of the wing of the airplane. Denoted by S
The Coefficient of Drag is given by the equation
Cd= D/(Pinfinity*S)
Now Substitute the value of P in the equation for the coefficient of drag.
We have
Cd=D/((0.5*d*V2)*S)
Now the drag force D is given by
D=Cd*0.5*d*V2*S
Thus from the above equation we can see that the drag force is directly proportional to the free stream velocity or the airspeed
Wiki User
∙ 16y ago
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Why is it easier for a plane to accelerate when taking off?
Because the force opposing the forward acceleration of the aircraft is drag, and drag is proportional to the square of the relative velocity. So when the airplane is accelerating from standing still, at first there is almost no drag force to oppose the acceleration. As the airplane increases its speed, however, the drag force increases rapidly. In steady flight, the drag force is exactly equal to the force being produced by the propeller.
Why drag increases as lift increase - for helis?
The production of lift creates induced drag. To create more lift, more airspeed is needed, and with airspeed, comes drag.
Can you change the four forces in flight in any way?
Of course. That's exactly how you steer an airplane. -- Running the engines faster increases the thrust, which increases the airspeed. -- Increasing the airspeed or the angle of attack increases the lift, which makes the plane climb. -- Increasing the drag causes the airspeed to decrease, which causes the lift to decrease. -- Decreasing the airspeed or the angle of attack decreases the lift, which can be used to lose altitude. -- Using control surfaces to increase the lift of one wing while decreasing the lift of the other wing causes the airplane to bank toward the wing with less lift. -- Increasing the angle of attack during a bank causes the plane to be 'lifted' around a turn. -- Extending flaps increases both lift and drag. If thrust is maintained at the same time, the airplane loses airspeed but maintains altitude. Anything you want the airplane to do is accomplished by manipulating the four forces in flight.
What is the aspect ratio of a high speed airplane?
Low! To minimize the drag which grow with the square of the speed.
What happens to total drag as airspeed is increased from the stall towards Vne?
Total drag in such a situation, initially decreases and then increases.
Induced drag on a airplane?
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars with airfoil wings that redirect air to cause a downforce. With other parameters remaining the same, induced drag increases as the angle of attack increases.Source of induced drag:Lift is produced by the changing direction of the flow around a wing. The change of direction results in a change of velocity (even if there is no speed change, just as seen in uniform circular motion), which is an acceleration. To change the direction of the flow therefore requires that a force be applied to the fluid; lift is simply the reaction force of the fluid acting on the wing.When producing lift, air below the wing is generally at a higher than atmospheric pressure, while air above the wing is generally at a lower than atmospheric pressure. On a wing of finite span, this pressure difference causes air to flow from the lower surface wing root, around the wingtip, towards the upper surface wing root. This spanwise flow of air combines with chordwise flowing air, causing a change in speed and direction, which twists the airflow and produces vortices along the wing trailing edge. The vortices created are unstable, and they quickly combine to produce wingtip vortices.[2] The resulting vortices change the speed and direction of the airflow behind the trailing edge, deflecting it downwards, and thus inducing downwash behind the wing.Wingtip vortices also modify the airflow around a wing, compared to a wing of infinite span, reducing the effectiveness of the wing to generate lift, thus requiring a higher angle of attack to compensate, and tilting the total aerodynamic force rearwards. The angular deflection is small and has little effect on the lift. However, there is an increase in the drag equal to the product of the lift force and the angle through which it is deflected. Since the deflection is itself a function of the lift, the additional drag is proportional to the square of the lift.The total aerodynamic force is usually thought of as two components, lift and drag. By definition, the component of force parallel to the oncoming flow is called drag; and the component perpendicular to the oncoming flow is called lift.At practical angles of attack the lift greatly exceeds the drag. Unlike parasitic drag on an object (which is proportional to the square of the airspeed), for a given lift, induced drag on an airfoil is inversely proportional to the square of the airspeed. In straight and level flight of an aircraft, lift varies only slowly because it is approximately equal to the weight of the aircraft. Consequently in straight and level flight, the induced drag is inversely proportional to the square of the airspeed. At the speed for minimum drag, induced drag is equal to parasitic drag.
What is power curve?
A power curve is an important curve used in aviation. It is the curve of form and induced drag interacting with airspeed. This curve shows pilots that they must give additional thrust as speed decreases to maintain airspeed when airspeed is below a certain point.
Induced drag in airplane is reduced by?
winglet
How does the drag affect the forward motion of the airplane?
Drag slows the forward movement of aircraft.
What is drag for an airplane?
Drag is a force that acts opposite to the direction of movement of an airplane. Drag is mainly caused by air. The other forces that act on the plane while moving in the air are thrust, lift etc..
When falling in air where air drag is sinificant why do heavy objects fall faster than lighter objects?
In that case, gravitational attraction is even more significant. Air drag depends on the surface, and for similar shapes, that is proportional to the square of the linear size, whereas the weight, and therefore the gravitational attraction, is proportional to the cube of the linear size.
What is the drag of an airplane?
The drag of an airplane is the air resistance caused by the plane flying through air. Similar to when you pull your hand through water and feel resistance.
