Quote:
Originally posted by NY Madman:
....In the original scenario the conveyor and the plane's speed effectively cancel each other out in the equation.....
"Speed" doesn't cancel.

Forces may cancel, but don't in this case.

This is not an aerospace engineering problem. An assumption is that the plane is already properly engineered. So we are back to Physics 101. Regardless, I wouldn't trust an aerospace engineer who has no grasp of basic physics (like the one you quoted).Please refer him to the physics professor quoted earlier.

It is disappointing that you have chosen to fanatically support the incorrect answer instead of taking a few minutes to understand this high-school level problem.

Please read the basic physics:

Quote:
Originally posted by JeffW:
Relavent information:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

Let's agree on what assumptions are sensible then. All of the assumptions below apply to virtually all aircraft.

Plane is powered by engines that push air (props or jets)
Plane's speed is measured by a windspeed meter as well as GPS
Plane's wheels spin freely
Wheel friction is negligible when compared to thrust
Newtonian physics apply



Coefficient of dynamic friction:

Force of friction:

F(f) = -uN

(negative because it opposes motion)

u = coefficient of static friction

N = weight of plane

Notice velocity is not included!

That means that the velocity of the conveyor belt is irrelevant for all practical purposes.

F(t) is force of thrust

a = (F(t)+F(f))/m

You won't find a scenario where |F(f)| is greater than |F(t)|. Therefore, in ALL cases the plane moves with respect to the atmosphere, thus achieving lift.

Possible scenario:

t = 0 :

Plane 0 mph
Conveyor 0 mph
Wheels 0 mph

t = 15 :

Plane 60 mph
Conveyor 60 mph
Wheels spin @ 120 mph

t = 55:

Plane 160 mph
Conveyor 160 mph
Wheels spin @ 320 mph

....

The plane takes off.

Either learn why it is correct or refute it....

..scientifically.