Did you ever know...that you're my heeeero?

Try this experiment -

get in the back of a truck

get the driver to go like 45-50

jump out in the opposite direction (maybe get a running start)

you should be fine - report back on how it goes

quote:

---

How much precious wetlands is this huge conveyor of yours going to destroy?

---

no, that would be RLEM majors.

Biology Majors - Why do I never get to practice what I preach?

quote:

---

I'm no where near an engineer. Doesn't a plane need wind moving over it's wing to take off? If the converor makes the plane "run in place" so to say, is there not any wind moving over the wings? If not, how does it take off?

---

You are correct. However, the plan would not be "running in place". The plane will move forward as a result of the thrust from the engine(s). It doesn't matter that the wheels beneath it are spinning wildly.

Again...imagine a plane on a sheet of ice. If the pilot guns the engines at full throttle, the plane is going to move forward, even though the wheels are sliding along beneath it.

Again, the wheels are irrelevant.

This is where you went wrong.

quote:

---

the converor makes the plane "run in place" so to say,

---

hth.

we prefer the term, "moot"

quote:

---

I'm no where near an engineer. Doesn't a plane need wind moving over it's wing to take off? If the converor makes the plane "run in place" so to say, is there not any wind moving over the wings? If not, how does it take off?

---

The conveyor does not make the plane "run in place." The plane engines propel the plane forward because they are "pushing" the plane. This "pushing" causes air to move over the wings.

I thought the conveyor belt was irrelevant. Which is it?

There is no spoon.

quote:

---

Biology Majors - Why do I never get to practice what I preach?

---

I'm not even sure what that means.

yet another post that was much funnier in my head

The irrelvance is moot.

I feel your pain.

chocolate labs

The moat is moot.

Racist!

Bubble Shields

Even though I think most of this thread is one giant troll I couldn't resist correcting you clowns.

No air speed over the wings=no liftoff. Unless you're going to put the exhaust down, like in a harrier or the JSF, if the conveyor matches the speed of the thrust, no liftoff. So-the wheels, the conveyor, and the thrust is all moot! Air speed over the wings is all that matters. I'll bet eleventy billion dollars on it.

the moot is irrelevant

quote:

---

No air speed over the wings=no liftoff. Unless you're going to put the exhaust down, like in a harrier or the JSF, if the conveyor matches the speed of the thrust, no liftoff. So-the wheels, the conveyor, and the thrust is all moot! Air speed over the wings is all that matters. I'll bet eleventy billion dollars on it.

---

Sigh.

Make your Eleventy-Billion Dollar check out to Tom Servo.

Jesus.

Experiment time:

Get a folder(flat object, whatever) and a pen. Place the pen on top of the folder and hold it out in front of you. Quickly swipe the folder out from under the pen horizontally.

Report back to me.

I can finally picture what ya'll are saying about the speed of the wheels not mattering. I found this and it helped me visualize it better:

quote:

---

All of the forward motion of the plane comes from the planes engines, which are in no way affected by the treadmill. The engines are grabbing air that is standing still in front of them, and pushing it away from the plane, the wheels are only along for the ride. Imagine if you had roller skates on your feet and were standing on a treadmill holding a stationary rope that outstretches in front of you. As the treadmill tries to push you backwards, your grasp on the rope keeps you stationary and your wheels spin. Now, someone begins to reel that rope in. The treadmill can try and compensate, but it only means your wheels spin faster, you will move forward in relative space. The same is true for the plane, only instead of grabbing a rope, the plane grabs the still air in front of it. If you were a passenger on such plane, you wouldn't even notice anything different was happening.

---

quote:

---

If a plane is traveling at takeoff speed on a conveyor belt, and the belt is matching that speed in the opposite direction

---

So is this is the key difference in the arguments?

The problem states that the conveyor belt matches the takeoff speed, not that it goes as fast as it needs to to hold the plane in place via the friction in the wheels or whatever the non-takeoffers are claiming.

This post grew way to fast for me to have an early comment... so here, here's my comment.

The conveyor is moot but the show should be interesting to watch though they're outcome will likely be wrong because an exact replication of the experiment will be pretty tough to pull off (large scale that is).

quote:

---

Jesus.

Experiment time:

Get a folder(flat object, whatever) and a pen. Place the pen on top of the folder and hold it out in front of you. Quickly swipe the folder out from under the pen horizontally.

Report back to me.

---

Attach a jet engine to the pen and report back to me.

I asked my dad, an airplane mechanic and engineer several months ago. His response:

Let us begin by saying that given a surface moving exactly the speed of the vehicle although in an opposite direction, the following will take place:

A vehicle, such as an automobile, having wheels directly powered by an engine will remain in place under the conditions you described since the "conveyer" is moving in the direct opposite direction at the same speed the vehicle would be traveling if it were on a non moving surface.

Conversely, the speed of an aircraft is a function of (among other things) the power output of the engines, which push or pull the aircraft by reacting against the air frame and are not in any way mechanically connected to the landing wheels. On takeoff, the aircraft can therefore accelerate to flight speed regardless of the direction the runway surface is moving (excluding sideways of course) as the landing wheels are theoretically free to rotate in either direction. Under your theoretical conditions with all other conditions being equal, the aircraft will take off, but the landing wheels will be rotating at twice the normal speed. Good luck with the wheel bearings and the tires.

He further pontificates:

The configuration of an aircraft, principally the shape of the horizontal surfaces ( wings , horizontal stabilizers, or in the case of the space shuttles, the shape of the fusilage underbody itself) is such that air at an appropriate velocity will provide pressure under these surfaces in excess of that over the same surfaces so that "lift" results. This can only be achieved by provision of forward thrust through a suitable power source. There cannot be an argument whether power or lift are more significant, since they are mutually dependent for sustained flight. Alternatives to sustained flight given these principles are:

Glide: Sustained flight with reduced or no power where sufficient forward velocity (due to gravity) is maintained to provide lift.

Crash: The result, in some instances, of failure to maintain sufficient power and/or lift.

Again, these principles are totally independent of the velocity of the aircraft over ground.

Please make this thread go away!!!!



[This message has been edited by Jersey Girl (edited 10/24/2007 2:14p).]

Dads

[This message has been edited by coltjimclemens (edited 10/24/2007 2:13p).]

conveyor matches ground speed of plane = flying plane...

conveyor matching tangent speed of the rotating wheels of the plane = catastrophic failure of conveyor, landing gear, or both... plane wrecks, people die, fire crews come out...Aggieland thinks it's a normal day at the firefield.

[This message has been edited by TexasRebel (edited 10/24/2007 2:15p).]

quote:

---

Attach a jet engine to the pen and report back to me.

---

I'm one of the ones who say the plane will take off. Just trying to get people to understand the concept of free spinning wheels on a convener belt.

Biology majors

karaoke

quote:

---

Just trying to get people to understand the concept of free spinning wheels on a convener belt.

---

if the conveyor is trying to catch up to itself and the speed of the plane, it will be moving SO fast that friction is no longer negligible....

don't forget friction.

Lee Majors