Yes or no

To keep the sprit of the problem, rather than using a conveyer belt (with which we cannot keep the plane in one place), I can conceive a plane with a restraining structure (that will effectively cancel the force due to the thrust). When the take-off thrust is reached (at which point, the plane is still at rest with respect to the earth), the restraining mechanism releases and plane effectively starts from rest. Will the plane take off?

No. Horizontal thrust mechanism can be installed on a truck and the truck never 'flies'. You need horizontal speed of the wings through air to produce the vertical lift.

The one that comes close to this type of system is airplanes taking off from an aircraft carrier. The horizontal speed is needed to have the 'lift', so they use a catapult to accelerate the planes (0 to around around 270 mph in 2 seconds). Even then, with heavier planes, you could see them dropping a bit right after it leaves the deck. Planes point nose high to compensate for the drop at the drop off from the deck.

 

No. With no airflow under the wings, there is no lift. no lift = no fly.

 

The more I think about this, the more I'm starting to think the plane will take off.

 

No

 

The simple truth is: the question is too ambiguous.

 

I change my answer. Yes it will take off. No matter what the speed of the wheels, the horizontal thrust will slowly gain speed. The conveyer belt can spin the wheels as fast as it wants but the plane will slowly gain speed in relation to the ground. Eventually, the wheels and conveyer might be spinning at 500 mph, but the plane will get up to 100mph and will be able to take off.

 

There's no implication that this hypothetical jet even has functioning engines,much less that they are operating.
In any hypothesis, if you add elements not described, you completely distort the question.
All we know is that the jet is on a conveyor. Unless the conveyor, itself, is moving the jet forward fast enough to provide lift (highly unlikely), the jet cannot become airborne.
There's no indication that this conveyor is moving, either.

 

Yes. It's not driven by the wheels

 

The explanation:

 

It does say sitting on the conveyor belt... sitting planes can't take off.

 

Okay....here's the deal. The conveyor belt is immaterial to the equation. The original question didn't make anything clear about what was making the wheels turn, but if the engines are providing enough thrust to move the plane forward, regardless of the speed of the conveyor belt and RPM of the plane's wheels, the thrust of the engines will propel the plane forward through the surrounding AIRMASS, and if this movement is at a sufficient AIRspeed to provide the required lift the plane will take off and fly. If, for instance, the takeoff AIRspeed is 190 mph and the conveyor is moving at 190 mph in the opposite direction, the wheels will be moving at 380 mph, but that is totally irrelevant to whether the plane will fly. In other words, conveyor belt speed and wheel speed don't matter. What matters is AIRspeed.

Actually, I think I'm taking this problem W-A-A-A-Y too seriously

 

However we don't know the jet even has working engines! So, there's NO air speed at all.

 

Yeah!

 

It was a Yes or No question.

 

You're thinking like a Ford owner.

 

Shove that right up your ford!

 

I can't believe how many people think the wheels help a plane fly?

 

Can a float plane take off upstream on a wide, flat water river?

 

Sure, with engines running and enough air moving over wings.

 

Thrust. Nothing to do with wheels. Aviation Fundamentals 101

 

Sean a !!!!!!!!!!!!!...LOL

 

The original intention of the puzzle is to make sure the plane reaches the take-off thrust and still not be moving. A conveyor belt can't do that. The only horizontal force that the conveyor belt exerts on the plane is friction. But in order to make the plane not move, the total horizontal force must be zero. Friction is not going to be able to match the thrust of a plane. It's just too small. That's why I thought a restraining mechanism (sort of like a super-duty harness) would be at least theoretically possible scenario.

If the plane does reach the take-off thrust and still stationary (let's say, using a harness), it is not possible for the plane to fly. In order to be able to take off, the upward force has to be greater than the downward force (weight of the plane). Thrust is horizontal (unless it's a Harrier jet, etc.). Upward force comes from the pressure difference between the upper side and the lower side of the wings due to air moving past it. When plane is not moving, upward force (lift) is precisely zero.

Of course, I assumed a simple picture (that thrust is horizontal, etc.).

 

I DON"T CARE!! I'm gonna have a beer.

 

I looked some stuff up (my kids finished their homeschooling for the year).

I didn't realize that there are so many different 747s. There's 747-100, 747-SP, 747-200, 747-300m 747-400, and several others.

Looking at 747-400, the most numerous model, the maximum take-off weight is little less than one million lbs. The static thrust is somewhere between 1/4 and 1/2 of its weight. This is a lot less than I thought (I am a novice when it comes to aviation). Given that the coefficient of static friction (under good condition) can be as high as close to 1, I now think it is possible for friction to counteract the thrust (at least in the horizontal force). Realistically though, a conveyor belt is not going to work (or work very well), but at least theoretically it seems possible.

If the plane is stationary with respect to air (even at full thrust), no take-off takes place. Airplanes has the stall speed. If its speed is less than this critical speed, it can't fly. For 747, the stall speed is around 120 mph.

 

Do you really think this aircraft would have a hard time taking off irregardless of a freaking conveyer belt scenario???? Give me a break.

 

Regardless of your failed grammar.

It will leak fuel all over the belt. Lol