Old Riddle

Shamrock

Hopefully this hasn't been posted before.

A plane is standing on runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same as that of the plane (but in opposite direction).

The question: Will the plane takeoff?

Big Dave

yes.

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Gordo

The laws of thermo-dynamics say no.

Common sense says no. Cuz the Navy would have implemented this scenario long ago.

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Peladu

Yes...she will take off.

IHI

You could be technically moving the tires at 180mph but if the air is not passing over the wings to create a negative pressure area needed for lift, then no it will not "take off" since essentially it's sitting still. Just like driving your car in the winter time and the ice acting as the conveyer for the equation: Sure your speedometer and wheel speed may indicate your going 120mph, but in reality your sitting still. Try it this winter and stick your hand out the window when your pulling away from the stop sign and the speedo say 100mph....does your hand react with the up and down movements forced by air flow across it?? heck no!!! SAME EXACT PRINCIPAL!!

This riddle is pointless with any amount of common sense. and like was stated by Gordo, if it did work they would not have these hitech launching devices on air craft carriers, it would just be a high speed conveyor belt.

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cssconstruct

since this is a riddle I will say yes.

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Tom R

And there's your answer.

Big Dave

Tom R may have something but as for my yes answer I stick to it.

The fact that the runway under the plane is moving in the opposite direction has no bearing on will it fly or not. The airplanes flight is not propelled by the wheels, it is propelled by the thrust of the engine moving it forward creating lift thus the wheels have no bearing.

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Tom R

Welp, - - lemme say this about that . . .

Even if the plane 'did' depend on the motion of the wheels, - - the fact that the runway was going in the opposite direction would actually DOUBLE the wheel speed . . .

Are we confused yet??

dougchips

Dave, the thrust is not really moving it forward it is maintaining it. So like IHI said no wind can lift the plane.

Tom R

I say this riddle's a Sham . . .

Big Dave

I'm starting to think the same thing.

I still stick by my answer.

edit: IHI what happens when you strap a jet engine to the car.

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Patty

Figures you guys would post these 'mind bogglers' while I am on Day #17 of some major meds.

Whatever happened to the cute, funny jokes you use to post?

dougchips

Dave, I glued a rocket motor to a remote control car once when I was a kid. The answer is it destroys the car and makes a kid cry. Actually it was 2 or 3 size d motors all at the same time. What is even worst is a model b-52 loaded with bottle rockets and cherry bombs trying to take flight from inside my 3rd floor bedroom. For some reason I don't play with fireworks any more!

Dustball

Plane is moving forward at 200 mph which means the wheels are rolling at 200 mph. Conveyor reacts by moving in the opposite direction at 200 mph. Plane is still moving forward at 200 mph since the speed of the wheels have nothing to do with how fast the plane itself is moving. In reality, the conveyor and wheels will continually ramp their speed up as the plane's forward speed increases from the jet engine thrust.

Tom R

Yeah, - - what he said . . .

dougchips

The plane would never obtain speed, the wheels would be spinning like mad and the thing would never go anywhere. Like if you tried to run up a down escalator if you matched it s speed you could run in place like mad and never move forward enough to achieve speed over ground.

Big Dave

Man you've got to forget about the wheels. When the thing is in the air the wheels don't keep it there.

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Teetorbilt

The two are irrelevant other than the aforementioned wheel rotation. The wheels will be rotating twice as fast but the plane will still rotate (take off) at the same airspeed.

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Tom R

Seems to me you'd be takin' off like a bat outta hell the minute the basement got filled up with steps . . .