A harmless little riddle

This is why it will fly- the treadmill cannot stop forward movement. Look at this to understand better

b u m p

Okay, the diagram of the rollerblade thing got me thinking again, and I emaileda friend of a friend who works for NASA. He called back, and explained that the diagram was bogus b/c the jets cannot provide forward motion and velocity if they are never thrusting the plane forward off of the treadmill.

You would think it is the same as if the plane was simply floating, but it is not. It has to have that initial forward movement to take off, which it would never have if the treadmill never allowed it to move forward.

So it would NOT take off.

To prove a plane won't fly, strap a box fan to a skateboard, and put the skateboard on a treadmill.

.. wrote:

b u m p

That was a dirty, dirty trick.

Holland Nass wrote:

To prove a plane won't fly, strap a box fan to a skateboard, and put the skateboard on a treadmill.

So, do box fans normally fly all over the place when not placed on a skateboard and treadmill?

???????? wrote:

So, do box fans normally fly all over the place when not placed on a skateboard and treadmill?

They probably would, given the absence of gravity and the resultant FRICTION...

Holland Nass wrote:

To prove a plane won't fly, strap a box fan to a skateboard, and put the skateboard on a treadmill.

that wouldn't prove anything since your standard treadmill does not have the ability to automatically match the speed of whatever is on it.

Think Harrier jet.

'Nuff Said!

QED wrote:

Think Harrier jet.

'Nuff Said!

Yeah, but if the harrier was tied down - inhibiting its movement up - it would not fly either

Straight Dope says it would take off... But it also states that it is a paradox, meaning that no treadmill can operate at infinite speed.

I say, "Whatever," this treadmill operates at infinite speed, or the question is null and void.

Staright Dope reasons that no treadmill can match that of the plane's jets, meaning the plane would take off.

Hmmmm...

My NASA boy still says it won't fly. You need the thrust.

hawksxl wrote:

that wouldn't prove anything since your standard treadmill does not have the ability to automatically match the speed of whatever is on it.

Please visit page one, where the hypothetical treadmill, one that can magically match the required speed, is presented as a part of the equation. This magic treadmill is also large enough for a plane.

For a further thought, take away the treadmill and prevent the wheels from turning. As the thrust is created exponentially, the plane would start to move, but the wheels and landing gear would disintegrate, and the resulting friction of the belly of the plane on the ground would also prevent the plane from flying.

Another Interested Party... wrote:

My NASA boy still says it won't fly. You need the thrust.

Is your NASA boy the tea boy, by any chance?

FYI, the plane moves because of the thrust. The thrust doesn't happen because the plane starts moving (first).

the way the question was STATED in the beginning, the plane will not fly. Now if for some precarious reason the plane has a way to stay on the treadmill with its free spinning wheels, then yes if you ADD the jets to it, it will take off....the only thing the question says is that the plane is moving at the same speed as the treadmill...with the free spinning wheels, it ain't goin nowhere...

huge big gigantic tall guy wrote:

Is your NASA boy the tea boy, by any chance?

FYI, the plane moves because of the thrust. The thrust doesn't happen because the plane starts moving (first).

I am glad you paid attention on your trip to the Smithsonian, but the point is that the plane is victim to friction, regardless of the thrust of the jets.

I am not sure what you are trying to say in your post...

He may be the tea boy for all I know...

researcher wrote:

the way the question was STATED in the beginning, the plane will not fly. Now if for some precarious reason the plane has a way to stay on the treadmill with its free spinning wheels, then yes if you ADD the jets to it, it will take off....the only thing the question says is that the plane is moving at the same speed as the treadmill...with the free spinning wheels, it ain't goin nowhere...

Here's the crucial bit of info from the OP: "As the plane starts its engines"

With the engines started, they will develop thrust. That is, the engines will force air out of the rear of the engines, and , with an equal and opposite reaction, will push the aircraft forward.

huge big gigantic tall guy wrote:

[quote]researcher wrote:

Here's the crucial bit of info from the OP: "As the plane starts its engines"

With the engines started, they will develop thrust. That is, the engines will force air out of the rear of the engines, and , with an equal and opposite reaction, will push the aircraft forward.

Yes, but as I just stated, the plane remains a victim of friction and gravity. therefore, the plane cannot move forward b/c even though the thrust is made by the engines, the plane needs lift from the air, which it can not get if it is not propelled forward due to the treadmill. To move forward, the plane needs to overcome the treadmill, which it can not do.

The plane is not floating.

has there been an answer yet?

please summaries this mung

Another Interested Party... wrote:

Yes, but as I just stated, the plane remains a victim of friction and gravity. therefore, the plane cannot move forward b/c even though the thrust is made by the engines, the plane needs lift from the air, which it can not get if it is not propelled forward due to the treadmill. To move forward, the plane needs to overcome the treadmill, which it can not do.

The plane is not floating.

What's holding the plane back? Friction? From what? The wheels? Consider that Aircraft designers have designed undercarraiges specifically so the aircraft can roll. Easily.