Will it Fly??

anyone have more of these?

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Sure.

How many times can you fold a regular 20lb, 8" x 10" piece of paper in half before it becomes physically impossible? OOPS! My mistake - it's 8 1/2" x 11". Sorry! 

Extra Credit - What will be the resulting thickness when you are done?

A common housefly is trapped inside a boxcar on a train traveling from point "A" to point "B", a distance of 120 miles, at a speed of 40 miles per hour. The boxcar is 60' long (interior dimension), and the fly spends the entire journey flying from one end of the boxcar to the other without stopping. When the train has reached its' destination, how far has the fly flown?

You are trapped inside a room with an unmarked door at each end, and no other means of entry or exit. Stationed inside at each door is a guard. One door leads directly to Heaven; the other directly to Hell. One guard ALWAYS tells the truth, and the other guard ALWAYS lies. You are allowed to ask the guards one question. What question can you ask that will tell you which is the correct door to lead you directly to Heaven?

Is the speed of dark faster or slower than the speed of light?


More to follow, but as always, please don't blurt out the reasoning behind your answer!

Some of the positions, statements and conclusions really have me confused and I know I am not alone .

Lets see now; if the treadmill is moving at speed X and the airplane's thrust keep the wheels moving at speed Y so that the plane is not moving at ground speed, just at the same speed as the treadmill then Y = X, not 2 X. If the treadmill is moving at 60mph the wheels have to move at the same speed or the plane will move forward or backward on the treadmill.

I am not an aeronautical engineer, a pilot or anyway connected to the aircraft industry, but I have always heard that a plane will fly due to lift, which is caused by air moving past the wings. If the plane is maintaining 0 ground speed, how is lift generated? Or do we turn the treadmill to face into an 80mph wind?

Well, to Bernie, since there is NO POWER to the wheels, the plane only moves IF either 1: The ground is moving or 2: the prop is pulling it through the air, thus the treadmill becomes tarmac, (non moving) the question postulates an impossible situtation. Planes move through air, they move by movement of air or by reaction, not by friction with the ground like a car or motor home

And as to some of the additional questions

The fly flew sixty feet

You ask either guard "Which door will the OTHER guard tell me is the door to Hell" then go through that door that is indicated. It matters not which guard you ask.

YES

I used to know the answer to the paper question but alas, I've forgotten

Karl said:

Sure.

How many times can you fold a regular 20lb, 8" x 10" piece of paper in half before it becomes physically impossible? OOPS! My mistake - it's 8 1/2" x 11". Sorry! 

Extra Credit - What will be the resulting thickness when you are done?

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How many times??  The same number of folds as you can do with a piece of very thin tissue paper.

Thickness??    The number of plies times the thickness of the paper used.

Believe it or not!  Try it.

carson FL

ps: one of these days I'll figure out the quote method.

BernieD said:

Some of the positions, statements and conclusions really have me confused and I know I am not alone .

Lets see now; if the treadmill is moving at speed X and the airplane's thrust keep the wheels moving at speed Y so that the plane is not moving at ground speed, just at the same speed as the treadmill then Y = X, not 2 X. If the treadmill is moving at 60mph the wheels have to move at the same speed or the plane will move forward or backward on the treadmill.

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You're not confused, you have it right for the original question and your explaination is succinct and to the point.

Don

Don Jensen said:

You're not confused, you have it right for the original question and your explaination is succinct and to the point.

Don

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OK, consider this. Why does a plane have wheels? They are there ONLY to allow movement on a solid surface when the plane is not airborne. They contribute absolutely no energy to the takeoff of the plane. As the problem is stated, the treadmill is a "DISTRACTION" and has nothing to do with whether  the plane will takeoff on not. It is the movement of the plane through the air that causes it to lift and takeoff. The movement  of the plane through the air is caused by the propeller moving air and in no way does the contact of the wheels with the ground contribute to the increase of of this movement through the air. The propeller has more than enough energy to overcome the rolling resistance of the wheels.

Of course the plane will fly!

Chet18013

Chet18013 said:

OK, consider this. Why does a plane have wheels? They are there ONLY to allow movement on a solid surface when the plane is not airborne. They contribute absolutely no energy to the takeoff of the plane. As the problem is stated, the treadmill is a "DISTRACTION" and has nothing to do with whether  the plane will takeoff on not. It is the movement of the plane through the air that causes it to lift and takeoff. The movement  of the plane through the air is caused by the propeller moving air and in no way does the contact of the wheels with the ground contribute to the increase of of this movement through the air. The propeller has more than enough energy to overcome the rolling resistance of the wheels.

Of course the plane will fly!

Chet18013

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After rereading all of the posts, I noticed one very important assumption that was made by all.  The wheels are free wheeling and have no friction transmitted to the axles and thus the airframe.  Under this unrealistic situation the wheels would roll for ever (perpetual motion) once they were rotating.  I overlooked this situation and applied a real world solution to a fictional application.  So under this scenario the plane would fly just fine alongside Peter Pan.  ;D
Don

Therefore, if there is no net forward movement of the wheels, there is no net forward movement of the wings and no air passes over them to create lift.  Under this scenario, of course the plane will not fly!

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Don,
There will be a net movement, regardless of the amount and direction of runway treadmill motion.  The propeller will pull the plane forward even though the treadmill is a moving surface, because the plane does not rely on its wheels for anything other than reducing friction with the runway surface.

A sea plane is able to take off for the same reason - the slippery water has no effect on the propeller's propulsion force and the plane moves over the water to achieve airspeed.

Maybe this will help:

Remove the wheels from the plane, then energize the anti-gravity device. Make the plane hover 1 foot above the ground. Rev the engine and go. Will the plane fly? of course.

    The wheels do the same thing as they are not holding back the plane.

carson FL

carson said:

one of these days I'll figure out the quote method.

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Looks like you've got it Carson.

RV Roamer said:

Don,
There will be a net movement, regardless of the amount and direction of runway treadmill motion.  The propeller will pull the plane forward even though the treadmill is a moving surface, because the plane does not rely on its wheels for anything other than reducing friction with the runway surface.

A sea plane is able to take off for the same reason - the slippery water has no effect on the propeller's propulsion force and the plane moves over the water to achieve airspeed.

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  I flew seaplanes in the military for a few years back when Fantasy Island was on the air.  I flew the big brother version of that airplane.  There is a huge amount of friction between the hull of the seaplane and the water.  So much so in fact, in certain situations if the pilot cannot break this friction (suction) and get on the "step" all you do is taxi around in the water until either you can get more lift over the wings or in case of the seaplane I flew, fire off a few bottles of JATO (Jet Assisted Take Off) to enable you to get on the step.  Once you're on the step, acceleration becomes much easier.  I bet Tom has seen this problem with his history of boats (without the benefit of JATO  ;D).  Again, if you make the unreal assumption of no friction, all bets are off.

Don

Don Jensen said:

I bet Tom has seen this problem with his history of boats (without the benefit of JATO  ;D).

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Sure have Don, and it's called "coming out of the hole". Of course, it only applies to planing hulls, because displacement hulls just push water aside. Sailboats OTOH can't decide what they want to do - go forward or lean over on their side.

BTW I've driven jet boats and jet skis; They sure get you on top of the water in a hurry. Different kind of jet of course.

Similarly with waterskis. First time someone towed me (on skis) with a jet boat, I not only came out of the hole, I came out of the skis.

Tom said:

Similarly with waterskis. First time someone towed me (on skis) with a jet boat, I not only came out of the hole, I came out of the skis.

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I bet that was just like a cork popping out of a champagne  bottle<<GGG>>.

Chet

LOL Chet, except I landed a bit harder than a champagne cork.

carson said:

Maybe this will help:

Remove the wheels from the plane, then energize the anti-gravity device. Make the plane hover 1 foot above the ground. Rev the engine and go. Will the plane fly? of course.

    The wheels do the same thing as they are not holding back the plane.

carson FL

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Well, of all of them, this one makes the most sense.  It really is about perception here.  In this case, how one percieves the original question.  It is certainly a trick question, but it is very interesting seeing all the responses.  And in the end, if I try and visualize it, I still cannot see that plane flying, even though I have convinced myself that it will.  Y'all have to quit doing things like this to us feeble minded!!!

But the folks who cite friction between the wheels and axle as keeping the plane from moving forward are overlooking the friction between the fictional faster than light treadmill and the air around it which will cause the air to move over the plane

There are several planes that can take off straight up

There have even planes take off backwards (however trust me you don't want to be flying in that kind of breeze)

If you have a lift off speed of 50mph and a ground wind speed of 100, You take off backwards

I have seen both (Though not at the same time)

You ask either guard "Which door will the OTHER guard tell me is the door to Hell" then go through that door that is indicated. It matters not which guard you ask.

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Wrong.

John, I misstated the 'fly' question. As stated, you are correct. I'll post the correct version of the question after I've screwed my head on properly.

My late father in law used to tell me about Lowell Bayles at the Springfield, MA airport in the 30's.  There was a 50 mph gale, so he got ten men to move a Taylorcraft BC12D out of a hanger.  While they held it, he started it up and advanced the throttle.  When he thought it was right, he signalled to let go.  He then climbed vertically, maneuvered left and right a few times, then landed back in the same spot.  Then the ten grabbed the plane, he cut the throttle and they dragged it back into the hanger.
Art

Chet18013 said:

and through some great engineering the runway is actually a giant treadmill. It's engineered so that when the plane starts to move forward the runway moves in the opposite direction at exactly the same speed., i.e. as the airplane's wheels pick up speed the runway matches it.

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"Remove the wheels from the plane, then energize the anti-gravity device. Make the plane hover 1 foot above the ground. Rev the engine and go. Will the plane fly? of course.  The wheels do the same thing as they are not holding back the plane."

We keep losing sight of the original question as stated. Don't forget, we are talking about some great engineering feat, the plane never moves. Wheel friction,  delays in matching the speed of the plane and the treadmill, wheel speed, thrust and all the rest of the arguments seem to continue to ignore the fact that the plane never moves. The wheels move, the treadmill moves, but the plane never moves.

Where does it get lift to get airborne if it isn't facing into a gale ??? ???

Bernie, of course the plane moves.  The wheels on an airplane are free wheeling and not powered.  The propeller provides the forward acceleration and it's irrelevant how fast the wheels turn.  As I said earlier, replace the propeller with a rope attached to a winch at the far end of the runway and start the winch turning.  The airplane will move forward regardless of the wheels and the treadmill.  Replace the wheels with runners and the treadmill with moving ice and it's easier to picture but the same logic applies.