Wrong, they would freely rotate.

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So that interpretation of the questio is just plain silly.

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The entire question is silly if you want to consider reality. A conveyor belt with the ability to hold the weight of a jet that can react to the wheels of the jet turning with no delay and no friction?

Yes, it's an impossible and silly question. A fun mind game nonetheless.

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If the plane is going 2 mph forward (in relation to the surrounding area) and the conveyor belt is going 2 mph backwards, then the wheels of the plane would have to sliding on the conveyor rather than just turning.

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Aircraft wheels are not powered. There is no mechanism whatsoever to transfer power from the engines to the wheels. There is no driveshaft to the wheels. There is no drive belt. There is no motorcycle type chain. There is no form of hydrostatic drive. The wheels on aircraft are free-wheeling.

It's kind of like the front wheels in a rear-wheel drive car.

[This message has been edited by eric76 (edited 12/4/2006 4:53p).]

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The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

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The problem does not say that the conveyor belt keeps the plane from flying, it just states that the belt velocity = plane velocity. If plane velocity = 0, Belt velocity = 0. If plane velocity = 100 mph, the belt velocity = 100 mph. The wheels will simply turn twice as fast (more or less).

The hypothetical does not say plane velocity = 100 mph and belt velocity = 'whatever is necessary to keep plane from moving'

velocity in relation to what?

in relation to the surrounding area? If so, then by definition the plane is moving regardless of any conveyor belt or anything else. If by problem definition the plane is moving relative to the ground, the plane takes off.

I, however, read it to mean that the velocity as what would be measured by tire rpm. If the rotation of the tires is exactly matched by a conveyor belt, then by definition the plane does not move forward unless the wheels also drag along the conveyor belt. I was assuming no friction in the wheel bearings therefore no capability for the wheel to drag and all forward thrust of the engines is then perfectly translated (by magic) to the conveyor belt.

FALSE!

If there was zero friction in the wheel bearings, you could just start the conveyor belt and run it backwards at whatever speed you wished (say 500 mph) after releasing the brakes.

The aircraft wouldn't move at all (assuming no wind).

Then when the pilot started the engine applied sufficent throttle to overcome wind resistance, the aircraft would move forward. Apply the usual throttle to reach airspeed, and the aircraft would take off.

[This message has been edited by eric76 (edited 12/4/2006 5:03p).]

If you do not understand the answer to this question, quit trying to. Leave it up to the Engineers and physics majors. There are many situations in life that "seem" one way and actually happen another. The understanding of physics and the behavior of the surrounding environment gives one the ability to prove what happens in a logical way, usually with mathmatical equalities.

GIVE IT UP

I did not see any wheels mentioned in the hypothetical.

I read it this way:

Belt Velocity = Plane Velocity

And not,

Belt Velocity = Whatever will prevent forward motion of plane.

Another question: Is the conveyor belt just rotating or is the entire apparatus moving?

so which side are you on? I assume the right one.....but then your statement is incorrect. I am not a engineer or physicist and I know the correct answer

All of my posts rely on the assumption that all forward momentum of the plane results in the wheels turning (because the plane is on a solid surface).

If the plane is on the ground, the thrust of the engines causes the plane to move forward which causes the wheels to rotate at the same linear velocity of the plane.

If the plane is on a perfectly constructed conveyor belt as we imagine, rather than the plane moving forward in relation to the ground, the plane's wheels turn at the same linear velocity as they would on the ground but rather than the plane making any forward progress, the conveyor belt negates it.

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I, however, read it to mean that the velocity as what would be measured by tire rpm.

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Aircraft use a pitot tube to measure speed.

Does it move forward?

Yes ... it always pays to plane ahead.

Visualize it this way.

A conveyor belt is moving southward at 20 mph. You have attached a wagon to a wench which would pull the wagon across the ground at 20 mph. Set the wagon 50' from the south end of the conveyor belt. Turn on wench. The wagon will proceed across normal ground at 20 mph and then onto the conveyor belt. I assure you the wagon will proceed northward and reach the north end of the belt without problem.

[This message has been edited by IIIHorn (edited 12/4/2006 5:29p).]

But we don't know if that's how the situation is set up.

Simply put there isn't enough information in the question to make a determination.

IIIHorn is making the assumption that when the question says "speed of the plane" it means "forward airspeed". That's a reasonable assumption, but alas, it's still an assumption.

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Col. Mustard in the library with the revolver

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Impossible..I saw him throwin' it in Miss Scarlett in the bedroom while Mrs. Peacock was filming.

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Impossible..I saw him throwin' it in Miss Scarlett in the bedroom while Mrs. Peacock was filming.

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Did somebody mention Scarlett?

I'd give up everything I own for a private week with her.

simple video proving the right answer, yes it takes off.

the paper simulates the conveyor belt (very crude simulation)
http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B

The engines on a plane have to overcome the friction of the wheels rolling on the ground. The plane will freely accelerate and the wheels will only offer rolling resistance.

However, the rolling resistance will be much more than normal for the velocity of air over the wings. If the air velocity over the wings is 100 MPH the rolling resistance will be the same friction as if it were going 200 MPH.

Since the rolling resistance increases at twice the rate of the velocity of air over the wings, the plane will reach its terminal velocity at a lower actual ground speed.

The terminal velocty in relation to the thrust the engines put out must be higher than the velocity of air needed over the wings to create enough lift.

Once the plane is off of the ground the friction will drop substantially and the plane should have a nice little jerk.

My rather limited knowledge makes me think the plane will not take off. You have to look at it from a relativity standpoint. Relative to the air around the plane (which cases the lift which makes the plane fly) the plane is not accelerating and has no velocity. Unless there are 150 mph headwinds, I don't think the plane will move... much less takeoff.

Edit: Ok, I rethought it. The question is misleading and I haven't read the whole thread. Is the conveyor moving relative to teh wings or the wheels? if the conveyor is moving such that a marked point on the plane stays even with a point on unmoving ground (ie the wheels are spinning as fast as they can (rotational terminal velocity), the plane will not take off. If the conveyor is moving with an equal but opposite velocity of the plane, it should take off because the wheels would allow the plane to move forward with the ground moving backwards behind it.

[This message has been edited by GarlandAg2012 (edited 12/4/2006 7:39p).]

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You have to look at it from a relativity standpoint.

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I am looking at it relatively. Relative to me (and all posting posting that it will take off), you are an idiot.

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I am looking at it relatively. Relative to me (and all posting posting that it will take off), you are an idiot.

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I didn't say it would. I said it MIGHT.

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simple video proving the right answer, yes it takes off.

the paper simulates the conveyor belt (very crude simulation)
http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B

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That was by far the most scientific experiment I've ever seen!

why are people still posting on this? Has anyone not said that the reason a plane takes off in the first place is because of the bernouli principle which causes lift for the plane to take off. Its as simple as that. Air moves faster over the top of the wing then the bottom blah blah blah (read

http://www.allstar.fiu.edu/AERO/airflylvl3.htm
Because the plane is not moving, no lift will be created, and it will NOT take off. its freakin simple as that...

I believe that the argument isn't whether or not the engines can reach the proper rpm...the argument has been whether or not the plane will move forward.

the plane will move forward, end of story. Thrust is applied to the air behind the plane, not to the wheels. If the conveyor belt mattered at all, then Bernoulli's principle would be false and the plane wouldn't be able to fly in the air either when there is no force at all on the wheels (excluding air resistance)

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why are people still posting on this? Has anyone not said that the reason a plane takes off in the first place is because of the bernouli principle which causes lift for the plane to take off. Its as simple as that. Air moves faster over the top of the wing then the bottom blah blah blah (read

http://www.allstar.fiu.edu/AERO/airflylvl3.htm
Because the plane is not moving, no lift will be created, and it will NOT take off. its freakin simple as that...

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What you're not realizing is that because of the wheels, it is possible for the plane to move relative to the air with the ground moving backwrads.

come on ags, get this thing to 5000 views

take that skateboard and fan in video and put it on a treadmill. If the treadmill is going as fast as the fan is pushing... it wont go anywhere. Will it?

Has golfer posted on it? that seems to do the trick!

Dan: yes it will.

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take that skateboard and fan in video and put it on a treadmill. If the treadmill is going as fast as the fan is pushing... it wont go anywhere. Will it?

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Well i think it depends on how you interpret the original question. If you say the belt goes such that the plane does not move forward, then you're right, but in my opinion, that's not what the question is asking.