The "Plane on a Treadmill" Question

[Happy Monkey]

Originally Posted by Flint

There is no "right" answer.

The right answer is the one that requires no magic treadmill. The plane takes off.

[hideouse]

Originally Posted by skysidhe

I guess I am just too stupid to get it then. Thanks hideouse. You tried.

You are a good sport Sky.

[skysidhe]

Originally Posted by hideouse

You are a good sport Sky.

[lumberjim]

yes there is.

dude.

if the plane is going 100 mph, and the track of the treadmill is also going 100mph.....then the plans'e wheels are going 100 mph......but they have no effect on the plane's speed because they rotate

[xoxoxoBruce]

Uh, wheels = 200, Jim.
The question was written to lead people into the wrong logic, rather than discarding superfluous information. It is a trick question, but there still is one right answer..... and many wrong answers.

[lumberjim]

Originally Posted by xoxoxoBruce

Uh, wheels = 200, Jim.
The question was written to lead people into the wrong logic, rather than discarding superfluous information. It is a trick question, but there still is one right answer..... and many wrong answers.

rotating 200 mph, yes. moving 100 mph as the plane carries them


relative to the earth, flint, as everything is.

[xoxoxoBruce]

Originally Posted by lumberjim

rotating 200 mph, yes. moving 100 mph as the plane carries them

Oh, gotcha. Yes, of course.

That channel wing would be very difficult and expensive to build, although with composites it might be feasible. But, like Maggie said, heavy.

[Flint]

"forward speed" relative to what? Not stated.

Of course, in #3 the plane can slide into forward motion, but that isn't necessary unless in addition to #1. In #2 it just takes off.

[tw]

Originally Posted by Flint

"forward speed" relative to what? Not stated.

The speed is obviously defined by this:

When the plane's engines throttle up, it begins to move forward,

Again, a reference to the equations F=ma and v=at . Speed does not exist on its own. Speed is a relationship between two references. Force (the "F") defines those two refeneces. Engine creates a force between airplane and air. Therefore speed is also created / measured between airplane and air. "Forward speed" is defined by that phrase

When the plane's engines throttle up, it begins to move forward,

Previously posted are the numbers to stick into those equations so that we know how long (t time) that engine (F force) must push the plane (m mass) to obtain minimum takeoff speed (v speed).

[lumberjim]

wow, maggie. here's more

why aren't these designs being applied to other aircraft?

[MaggieL]

Originally Posted by lumberjim

why aren't these designs being applied to other aircraft?

Well...it looks gooofy, and aviators can be surprisingly conservative. The engineering of it is tricky...I suspect the wing shape has a weight penalty. And once you're airborne there's usually plenty of lift available, as long as you're willing to trade it for induced drag.

It's a rockin' performer on takeoff, but I bet the efficiency blows dead goats in cruise. Nonetheless, Custer apparently sued Fairchild claiming the A-10 Warthog violated his patent.

By the way, The MidAtlantic Air Museum at the Reading Airport has a Channelwing...not currently flyable.

[Griff]

Originally Posted by MaggieL

..not currently flyable.

... as it was mistakenly parked on a treadmill.

[MaggieL]

Originally Posted by Griff

... as it was mistakenly parked on a treadmill.

Nah, it was just left out in the weather for like forever.

[lumberjim]

how fast would a standard jet have to turn it's engines in order to pull enough wind over its wings to generate lift? assuming it stood still relative to the ground?

[glatt]

They are mounted under the wing, so they couldn't do what you describe. The airflow has to be above the wing.