Puzzles,conundrums, riddles and thoughts?

[Ziggy Stardust]

A plane is standing on a 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 (but in the opposite direction). Can the plane take off?

 

[Sidhe]

An airplane is on a conveyorbelt. The belt matches the speed of the airplane but in oposite direction. When the plane tries to take off, will it succeed?

no, there will be no lift if the plane is not moving forward so it will remain on the ground.

Lift is created as air travels over the planes wings, because of the shape of the wings it passes at different speeds over top or bottom, creating a decrease in air pressure above the wing and so causing lift, however it would be required to be moving for this effect to happen. Otherwise the air will not move over the wing quickly enough to create any appreciable lift.

 

[Ziggy Stardust]

I edited to make it a little more clear.

Sidhe, if the plane is not moving, how fast wil the conveyorbelt move?

 

[nonconformist]

Would the engines cause enough air movement as to provide lift?

 

[Sidhe]

Would the engines cause enough air movement as to provide lift?

Its's not the movement of air through the engine that causes lift it's the difference in shape of the wing on top and bottom.

I edited to make it a little more clear.

Sidhe, if the plane is not moving, how fast wil the conveyorbelt move?

What I mean is it has no directional movement, so it is not moving forward, movement in distance if you like or a vector, if the plane is at a stand still the conveyor belt is not moving, as it speeds up though the conveyor belt reacts accordingly keeping it's distance travelled at zero, thus it is not moving and the air is not moving over the wing sufficiently enough for it to take off, thus no it can't take off unless it is travelling forward at an apreciable speed, which is a lot more than a few mph. I think it's about 120 mph IIRC.

 

[Ziggy Stardust]

Would the engines cause enough air movement as to provide lift?

Nope.

Its's not the movement of air through the engine that causes lift it's the difference in shape of the wing on top and bottom.




What I mean is it has no directional movement, so it is not moving forward, movement in distance if you like or a vector, if the plane is at a stand still the conveyor belt is not moving, as it speeds up though the conveyor belt reacts accordingly keeping it's distance travelled at zero, thus it is not moving and the air is not moving over the wing sufficiently enough for it to take off, thus no it can't take off unless it is travelling forward at an apreciable speed, which is a lot more than a few mph. I think it's about 120 mph IIRC.

Sorry, wrong .... I can't yet say why though

edit: Since it's a yes/no question, the first with the right explenation will get to do the next riddle.

 

[nonconformist]

Its's not the movement of air through the engine that causes lift it's the difference in shape of the wing on top and bottom.

But the engine would cause some appreciable movement of air over the wings; i.e the pressure behind the engine would be a lot more than that in front.

 

[brennan]

If it is stationary wrt the air then no. Unless it's a Harrier or other VTOL plane.

 

[Sidhe]

But the engine would cause some appreciable movement of air over the wings; i.e the pressure behind the engine would be a lot more than that in front.

Maybe but nowhere near enough to cause it to take off I would of thought.

But if it can then that's your answer, noncom, I seriously doubt it though, but I could be wrong.

If it is stationary wrt the air then no. Unless it's a Harrier or other VTOL plane.

I thought of that but it's a stupid answer so I didn't say it.

Nope.
Sorry, wrong .... I can't yet say why though

edit: Since it's a yes/no question, the first with the right explenation will get to do the next riddle.

If the conveyor belt is moving would it create some sort of lift by moving the air over the wings by it's movement, thus yes it would take off?

 

[Ziggy Stardust]

But the engine would cause some appreciable movement of air over the wings; i.e the pressure behind the engine would be a lot more than that in front.

True, but that presuredifference won't be enough to create lift.

If it is stationary wrt the air then no. Unless it's a Harrier or other VTOL plane.

Nope, normal plane. It still takes off though.

 

[Sidhe]

True, but that presuredifference won't be enough to create lift.

Nope, normal plane. It still takes off though.

I edited above is this right? As the conveyor moves, it moves the air above it, which causes the air to move over the wings providing enough lift once it reaches a good speed to allow it to take off.

 

[nonconformist]

Aparently, it will

 

[brennan]

I edited above is this right? As the conveyor moves, it moves the air above it, which causes the air to move over the wings providing enough lift once it reaches a good speed to allow it to take off.

You wouldn't get enough friction to move enough air.

 

[Ziggy Stardust]

I edited above is this right? As the conveyor moves, it moves the air above it, which causes the air to move over the wings providing enough lift once it reaches a good speed to allow it to take off.

Nope. The air movement wouldn't be enough to create the lift.

Aparently, it will

Link doesn't work for some reason.

You're not cheating are you?

 

[Sidhe]

Aparently, it will

Then it's your riddle. Live and learn.

That link times out by the way.

 

[Ziggy Stardust]

Bah ... cheat0rz

 

[brennan]

Aparently, it will

That's an opinion. And it's wrong. The air will not be moving relative to the wings. No lift, no take off.

Edit:

Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air

Is this plane moving relative to the air? Nope...

 

[Riffraff]

the important thing about the airplane riddle is, that the conveyer belt will only affect the movement of the wheels, but not that of the plane. The wheels don't accelarate or decelerate the plane, that's up to the engines. The wheels are simply there to minimize friction and for stability. With the conveyer belt moving in the opposite direction of the plane, the wheels will spin twice their normal speed; the motion of the plane is unaffected though.

 

[Ziggy Stardust]

Brennan, can you push a trolley on a moving walkway forward?

In case of the plane, see yourself pushing the trolley as the engine. If both the walkway and the trolley move at 5 mph, it only means the wheels spin at 10.

If the airplane was accelerated directly by moving the wheels to gain speed, it would have gone nowhere.

 

[brennan]

Brennan, can you push a trolley on a moving walkway forward?

In case of the plane, see yourself pushing the trolley as the engine. If both the walkway and the trolley move at 5 mph, it only means the wheels spin at 10.

If the airplane was accelerated directly by moving the wheels to gain speed, it would have gone nowhere.

Is the plane moving relative to the air? If the answer is no, then you have a grounded plane because there is no lift. That site makes the same irrelevant argument wrt the wheels. The wheels are not the issue.

It looks like you are making the case for the plane not being stationary, am I right?