plane on a conveyor belt?

[SteveBailey]

Originally posted by lukster
Ok, I'm glad you used the word spinning in regards to the conveyor belt. For the purpose of clarity take the belt out of the picture and just set the plane on the convey belt's wheel. This is the part of the belt that "spins", the belt itself only moves horizontally. If the belt spins in the opposite direction but at the same speed from the plane's wheel then plane's wheel will stay in place. Spin the belt wheel in the same direction and the plane's wheel and you will get the effect you described.

Right!  For the sake of the argument, our original poster is implying that the conveyer belt will match the speed(energy) of the wheel spin, but in the opposite direction, right?

At the point where the wheel touches the conveyer, the wheel(energy) is moving toward the back of the plane.  Therefore, if the conveyer is countering the movement(speed) of the wheel, the conveyer would move at the exact same speed toward the front of the plane.

Ergo, the wheel  speed would be 0 while the conveyer would match the air speed of the accelerating plane.

lurker, I'm thankful you thought this through.  

[lukster]

Originally posted by SteveBailey
Right!  For the sake of the argument, our original poster is implying that the conveyer belt will match the speed(energy) of the wheel spin, but in the opposite direction, right?

At the point where the wheel touches the conveyer, the wheel is moving toward the back of the plane.  Therefore, if the conveyer is countering the movement(speed) of the wheel, the conveyer would move at the exact same speed toward the front of the plane.

Ergo, the wheel  speed would be 0 while the conveyer would match the air speed of the accelerating plane.

lurker, I'm thankful you thought this through.  

See my edit. When it comes to wheel and belt rotation let's use clockwise and ccw to describe their movement. For the belt to negate any rotation of the wheel it would have to turn clockwise the same as the plane's wheel. That is not opposite.

[SteveBailey]

The rotation would be the same but that's not what the original poster is implying and that's why I siad it was oddly worded.

The OP is implying the the conveyer is acting against the spin of the wheels.  As a result , we need only consider the top of the conveyer for this, not the rotation of the conveyer.

That the OP is using the treadmill analogy further clouds the issue.  
On a treadmill, thrust is being applied to the "ground".  In the airplane scenario, only the wheels being pulled along by the prop against the unmoving earth cause the wheels to spin.

[lukster]

Tangent time, here's a little puzzle. Why can you always say that a plane's wheel will always rotate clockwise when the plane is rolling forward on the ground?

[lukster]

Originally posted by SteveBailey
The rotation would be the same but that's not what the original poster is implying and that's why I siad it was oddly worded.

The OP is implyiong the the conveyer is acting against the spin of the wheels.  As a result , we need only consider the top of the conveyer for this, not the rotation of the conveyer.

The belt moves the same direction as the surface of the wheel spinning it. Substitute a really big wheel in place of the belt and the result is the same. The wheel needs to be large enoguh for the plane to see where it is sitting as relatively flat.

[hitech]

Originally posted by lukster
Tangent time, here's a little puzzle. Why can you always say that a plane's wheel will always rotate clockwise when the plane is rolling forward on the ground?

Because most of us are right handed?

HiTech

[SteveBailey]

Originally posted by lukster
Tangent time, here's a little puzzle. Why can you always say that a plane's wheel will always rotate clockwise when the plane is rolling forward on the ground?

If the plane is taking off from your   right to left the tires would be spinning counter clockwise.

[lukster]

bzzzzt! wrong


Does a plane have a left and right wing? Do they swap places relative to where someone outside the plane is standing?

I just realized only the left wheel will spin cw, the right will always spin ccw, my bad.

[hitech]

Eskimo2: Finally looked at your 2 speed avi, very nice experiment showingwhat we are talking about.

HiTech

[SteveBailey]

Originally posted by lukster
bzzzzt! wrong


Does a plane have a left and right wing? Do they swap places relative to where someone outside the plane is standing?

I just realized only the left wheel will spin cw, the right will always spin ccw, my bad.

Well for my perspective, I consider the wing orientation to be relative to a pilot, facing forward in the cockpit so: no, they do not swap.

Your wheel spin theory implies that was are considering a pilot's perspective as well, right?

[lukster]

It's traditional, at least this is what I was taught in the AF, for all aircraft parts to be referenced from the pilot's perspective.

[Casca]

Originally posted by rabbidrabbit
A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off. This conveyor has a control system that tracks the plane's wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

In the opposite direction to wheel spin or airplane movement?  And is the speed of the "opposite direction" is determined by aircraft speed or wheel speed?  You can't tell from the question.


Initially I construed the question to agree with the Boortz article of Dec. 9th posted by Sandman which is one logical construction for the doubly ambiguous question.  That article reads:

A riddle was proposed on the Neal Boortz show today:

If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?

I somehow suspect that this is the question that Rabidrabbit was attempting to ask but I'm not inside his head.  The answer to that question is that the airplane will take off normally with the wheels spinning twice as fast.  The belt moves in opposition to the motion of the aircraft.

If the question is answered litterally as written the airplane will take off normally with the wheels motionless.  The belt moves in opposition to wheel spin.

The last possible interpretation is the conveyor moves equal and opposite to wheel speed irrespective of the speed of the airplane.  If you read it like that you wind up in your basement filming a belt sander documentary.

This thread is rapidly assuming a Swiftian dimension.  Recall that the kingdoms of Lilliput and Blefuscu were at permanent war over the correct way to eat a boiled egg:  From the round end or the sharp end.

For the most part everyone is correctly answering the question they see.

[lukster]

Round end obviously.

[Casca]

Wrong.  Anyone knows it's the sharp end.  

[SteveBailey]

If the question is answered litterally as written the airplane will take off normally with the wheels motionless. The belt moves in opposition to wheel spin.

What I said! (And I think Caveman too)