that isnt the question.
It is that the plane is moving at the same speed as the treadmill and vice versa, not faster than the treadmill.
If the plane moves forward on the treadmill, that means it is going faster than the treadmill.

If you suddenly start the treadmill, the plane will eventually start to move backwards, until the engines push it to the same speed as the treadmill.

It doesnt matter if there are wheels or not, if it is sliding on its belly, and the engines are pushing the plane at the same speed of the treadmill, It stays in the same place, with no air resistance under the wings.

All you guys are saying is that the plane can move faster than the treadmill, yes that can happen. But that is not the question.

I understand the physics of a plane taking off.
You arent understanding the question.

If you arent explaining with the actual question in mind, then there is no reason to try and explain it.

[QUOTE]Originally posted by chumpmann:

I understand the physics of a plane taking off.
[/QUOTE}
For some reason I missed your explanation, would you be so kind to please post it again?

Close, but wrong.

as the treadmill increases speed, the plane does NOT increase power to the thrusters. In order to stand still, the plane need only provide enough thrust to overcome the friction of the wheels on the tread belt. The thrust at low treadmill speed is the same at a high treadmill speed. The plane is not making the wheels spin, the treadmill is.

This would be analgous to tethering the plane to a fixed object. The treadmill can go as fast as it wants, as long as the plane remains stationary. The wheels will spin faster and faster, but fast spinning wheels does not make a plane take flight.

New analogy :rolleyes:

lets make this our plane:



and this is our "treadmill"



its well known that even against the current, this plane does take off.

This is where the "it takes flight" crowd ignores the fundamental purpose of a treadmill. They are using runway sized treadmills which is totally cheating. Treadmills are designed to keep the object on it, stationary.

A conveyor belt ..yeah I'll agree. But this is not the conveyor belt thread. This is the treadmill thread. And planes cannot fly on a treadmill. On a treadmill, the plane says at fixed latitude and longitude ... and subsequently .. a fixed altitude becuase it won't frickin take off

Since most treadmills have wheels on the underside, the airplane will push the treadmills, since the wheels will hook the handles, along the runway until it takes off.

The plane remains in one place according to the treadmill, but in space the plane is moving creating lift to take off

Taking off upstream is a lot different. The water places a far larger drag on the landing gear. With engines that are powerfull enough, the plane will take off.

Incorrect.

As has been suggested above, it would be a good idea to take High School Physics I prior to commenting.

You will not that the equation for frictional force is F(f) = Mu x Weight . By using standard physics equations, (as has been well explained above), the plane takes off.

Please do everybody a favor and take the time to read and explanation before making the foolish assumption that free-spinning wheels will affect the plane's absolute velocity. Wheel friction is insignificant compared to 50 tons of thrust. The plane takes off.

and you should take reading comprehension. I didn't say shit about the plane taking off. In fact, I supported your arguement you dumbass.

Actually I said that it does NOT affect the way the plane takes off.

I was stating that more thrust is not needed to make the wheels go faster .. ie .. I'll save you the comprehension part and spell it out for you: thrust of the plane is independant of the spinning of the wheels.

as the plane applies more thrust, its going to move forward no matter how fast the tread belt is going.

MY arguement is that using a runway sized treadmill totally defeats the purpose of using a treadmill. People like you are redefining what a treadmill is so you can spout physics lessons and try to make people feel stupid.

landing gear ...

fuck it. the treadmill sinks.

I still bet it doesnt take off.

How come you changed your arguement/side?

The length of the treadmill has absolutely ZERO bearing on the question.

in case you're serious .. why not?

Ding Ding Ding we have a winner! Finally somebody who realizes if the plane is moving forward at all then the plane is going faster than the speed of the treadmill.

Good God...you make my brain hurt.

Because the plane moves regardless of what the treadmill is doing.

Why would the length matter?

Why would a ten foot treadmill be any different than a 20 foot treadmill?

The wheels are NOT a part of the drive system of a plane.

Put dyno's on the front AND rear wheels of the plane. SAME thing. The plane will move OFF the dyno.

OK. I'm confused.. (not really)

Once again, since the obvious things didn't work...

If a plane is flying at 80 mph (close to stall speed of a Cessna), directly over a treadmill (as long as a runway, so there's enough space to do the test) that is currently running at 80 mph, the two objects are moving at the same speed, are they not?

Ok. So that's confirmed; the plane is flying over the treadmill at 80mph, as the treadmill is moving at 80mph.

Next step. The plane lowers his altitude *just* enough so that his tires are in now contact with the treadmill. The plane continues at 80mph forward. The treadmill continues at 80mph in reverse direction as the plane. BUT, you'll notice, the tires of the plane are now revolving at 160 mph equivalent.

So, multiple choice question:

The plane at this time is now moving at:

(A) 0 mph
(B) 80 mph
(C) 160 mph

If you guessed (A) or (C) you would be incorrect.

The correct answer is (B). Therefore the plane has forward movement at the same speed as the treadmill, in the opposite direction. The tires have an angular velocity of the plane's speed and the treadmill's speed, equivalent. But the plane only has 1 speed: 80 mph.

Angular velocity and velocity are NOT the same thing. They are a product of each other in the case of a wheel, but they are not a 1:1 relationship. They do not add or subtract directly to cancel each other out. Ever. Angular Velocity is the forward velocity divided by the circumference of the tire.

In this particular example, at 80 MPH, when you do the math, you'll find the tires will be spinning (angular velocity) (18.368) / (radius of tire) in radians per second. So if it's a 2' tall tire, the observed motion of the tire is that it's spinning at 36.7 radians per second. You don't observe the MPH equivalent the tires are spinning; it's a DEPENDENT property. The INDEPENDENT property is the net velocity (the sum of the airplane and the treadmill velocity).

In other words, the tires spin as a result of the horizontal motion of the airplane and the treadmill. It is a DEPENDENT motion. It is not physically measurable in "MPH", but is physically measured in RAD/S or DEGREE/S, and then converted using the radius of the tire to a MPH. You have to sort that out in your head, and be able to realize that angular velocity does not EVER get added or subtracted to motion velocity at any time; you can't act like they're the same thing, and add an independent to a dependent; math doesn't work that way, as it's a physical impossibility.

Whoops. Almost forgot. To finish it off, the very next second after proving the airplane will still continue forward at 80 mph, even if his tires are on a moving surface that's moving at negative 80 mph to him, the pilot pulls back on the stick, and viola: THE PLANE TAKES OFF...

If you REALLY want to think about it another way...Take this same example, only the treadmill is moving FORWARD at 80 mph. As the plane touches down onto the treadmill, the plane is moving forward 80 mph, the treadmill is moving forward at 80 mph, and the tires are rotating at a whopping 0 rev/s... The tires stand still, yet the plane is moving at 80 mph forward... And it still takes off. Example/Proof, yet again, that the angular velocity the tires move does NOT control the forward motion of a plane...

And one more, 'cause I just can't resist...Treadmill moving forward at 40 mph, plane moving forward at 80 mph. Plane touches down, and the wheels are only revolving at 40 mph equivalent, yet the plane is still moving at 80 mph... Oops. Lookie lookie...angular velocity of the tires still doesn't control the plane's movement...

But just in case I haven't annoyed you enough, yet..

Let's look at the case when the treadmill goes forward, and let's assume the argument of the "can't fly" bunch... If the plane moves at the same speed as the conveyor in the "backwards running conveyor", y'all have assumed the plane can't take off, 'cause the tires are moving at the same speed as the conveyor.

So, if the conveyor is moving forward at 80 mph, and the tires are moving forward at the same speed (80 mph equivalent), how fast is the airplane going?? If you said 80 mph, you'd be incorrect... the plane would be moving twice as fast as the conveyor, it'd be 160 mph!!

[insert "can't fly" protest]Argh!!! It CAN'T be moving at 160 mph, 'cause the tires are moving at the same speed as the conveyor!! But..........but I don't understand....[/insert "can't fly" protest]

Yep, that's right... the angular velocity of the tires isn't the same thing as the speed of the airplane... And since that's true for the conveyor moving forward, then it's true for the conveyor moving backward as well.

Guess what? The plane takes off.

If the tires are going 160mph how fast is the treadmill going?

80 mph. You don't do so well with the reading comprehension, eh? That was given in the example problem statement...

It says pretty clearly:

Typo.
Fixed.

Now let's assume, it's not a plane but an ostrich running on the treadmill.
The take-off speed of the ostrich is 120mph, and the treadmill is moving backwards at 80mph.
How fast does the ostrich have to run in order to take off?

The question isnt about wether the plane can touch and go.

It is asking if it can take off.

If the plane can move at all, then it can take off. I don't have to run a calculation on how long the runway has to be in order for it to accelerate to lift-off speed. I only have to prove it can move at all. The distance it takes is of no consequence.

If it can move at all, then it can get enough speed to take off.

And if it can move under a "touch and go" scenario, then it can move from standstill, as well. The physics that allow it to move at all are the EXACT same, regardless to the initial velocity being 0 mph, 50 mph, or 2,000 mph.

He has to run 200 MPH EQUIVALENT, or 120 mph ACTUAL. If he had an internal speedo, it'd say 200 mph, and to the ostrich, it doesn't really matter, 'cause he can't fly in the first fucking place. He's an ostrich.

Stop smoking crack.

This has already been explained.

If the plane isn't moving, than the treadmill doesn't turn. The plane does move and it takes off. It has been exaustively explained that the treadmill only adds some extra wheelspin. Please read the abundance of information posted on this subject and retort.

Anybody who can't understand a simple High School Physics problem doesn't need anybody to make them look stupid. They're doing a pretty good job on their own..........