crazymjb

The question should be will the plane move forward... At first I thought no due to how it was worded, but it will in fact move forward.

Mike

Pure Adrenaline

iTrader: (2)

One flaw there, buddy.

To use your example with the treadmill and the toy car, as you hold the car steady, the wheels are spinning in the forward direction, as the treadmill belt is moving backward. Overall movement of the vehicle = zero.

Now like you said, if you move the car forward with your hand, then of course it will move forward. But then again, what part of this in the original post did you not understand?

Once again, to use your example, the rules are that as you move the car forward with your hand, the conveyor belt would spin faster to offset that movement, which means the overall movement of the toy car remains at zero.

Let me ask you this. Take a radar gun and measure the speed of the toy car as it runs on the treadmill. I don't care if it's spinning at 1 mph or 100 mph. What do you think the radar will indicate, as to the moving speed of the vehicle? Zero.

Replace toy car with airplane. Actual movement of the airplane = zero. Which means zero amount of air is moving around the wings, which means no lift. No lift means no take-off, no flight.

crazymjb

Wait... I think I rescind my above statement. If the convener belt is INSTANTLY moving to match the wheel speed than the aircraft could not move forward... Because if the wheels are moving forward, they are moving faster than the conveyor belt at that point in time... But if the convey belt is instantly matching, or is always matched to their speed, than they cannot move forward.

Mike

S A CHO

This question has 466 pages on a Physics forum .... The answer has to be in there somewhere.

http://forum.physorg.com/index.php?showtopic=2417

S A CHO

<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/l__kEcvDir0"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/l__kEcvDir0" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>


/thread

JT Money

The only analogy that I could think to explain this the best is; Instead of the treadmill being flat it is angled down. The plane will continue to the end of the treadmill, with out using the turbines. This is beacuse of gravity. The wheels would cancel out enough friction so the plane would continue.

Now lets go back to the original question, all of the same principles are being used. Instead of gravity the turbines would send the plane down the treadmill.

crazymjb

Again it really depends on this one aspect... The time it takes for the conveyer to match wheel speed increase.

The main "loop-hole" in the argument that I can use is that the conveyor and wheels cannot be moving at the same speed and have one or the other make any progress. So from that physical impossibility, the wheel speed would not be able to increase without the universe coming to an end or some crazy shit like that.

Now if they conveyor is only matching the speed of the actual aircraft, than it could take off.

Mike

FuriousGeorge83

Why wont this thread die. I thought we all agreed that it could take off.

Pure Adrenaline

iTrader: (2)

I'm not convinced that it could take off.

My buddy is actually a pilot and I asked him tonight. He called you guys dumbasses for believing that it could take off. By no means he flies jet planes or anything like that, but he is a pilot.

Pure Adrenaline

iTrader: (2)

Turbine produces thrust. Thrust moves the plane forward. But this movement is offset by the conveyor belt moving the other way. Once again, the plane itself does not move. Only the wheels would spin faster (and the conveyor belt, as well) when you turn up the turbines. The plane itself does not move. No movement = no air = no flight.

Let me summarize for you... the turbines only produce thrust to move forward. That is all it can do. Unfortunately this energy is offset by the conveyor belt moving the other way. You are not achieving any kind of air flow or lift. You need lift to take off. Forward movement by thrust and vertical movement by lift are two different things; and we need both to fly. We're only achieving one here.

FuriousGeorge83

I dont understand why this is any different from a water plane taking off from the water. I guess the question would be if a river wheels spin, belt moves, plane stands relatively still. Add thrust from jet engines and the thing moves foward. Some one call mythbusters and have them figure this out.

FuriousGeorge83

nvm I think this kind of explains it thouroughly. I always assumed that since this was a theoretical question, the wheels where built to handle the high speed that where supposedly involved. I mean if they could build a treadmill that works this way, why not wheels and tires that have lower/minimal friction rates.

http://www.salon.com/tech/col/smith/...skthepilot215/

JT Money

People that think the plane won't take off please check out the link. It does a pretty thorough job explaning everything.

neyeswhip

iTrader: (2)

I think most knew the plane would take off assuming it was going to move. It was really a trick on words because it was saying the treadmill will keep the plane still despite the thrust of the engines. You have to realize that engine thrust does not equal drive of wheels. Realistically, the wheels cancel out the conveyor eventually and the engine thrust provides the forward motion for lift from the wings.

crazymjb

Well it MUST be specified the conveyor belt is matching aircraft speed and not wheel speed...

So yes, the plane will take off. A 747 takes off at 180 miles per hour, so the belt would be moving 180 in the opposite direction, and the wheels would be spinning as if they were going 360 over a normal runway... Assuming the wheels and tires are up for this, and the bearings don't overheat, we are good to go.

Now IF you say the conveyor speed is matching the WHEEL speed. Than that is where problems arise. So if the aircraft speed has to be 180 MPH to take off, and the belt is trying to match wheel speed, we are left with: [180 + S = S such that S greater than or equal to 180], an impossible equation in reality.

Mike

is300eater

I'm wondering if this theory can be tested with a R/C plane on a treadmill...

fla-tls

Oh man - not this thread again.

My assumption was that the plane was a bomber and that the shaking from the tread mill would shake one of the bombs loose and blow up the plane - killing all of the snakes inside.

So therefore, this whole thing is pointless.

bigman

at above post.

Hojo061782

I don't understand why this is so difficult.

The spinning rate of the wheels has nothing to do with takeoff speed. Takeoff speed only relies on the speed of the airflow over the wings. Speeding up the treadmill does not speed up or slow down airflow, it merely means the wheels will spin faster or slower. Technically you could have a treadmill moving in the same direction of the plane causing the plane wheels to not spin at all and yet have the plane take off. Also, because it's only airspeed that matters, an plane that takes off into the wind would theoretically have a lower stall speed than one taking off with the wind.

IlliNorge

A plane moves forward due to thrusts of air, much like a horizontal rocket. A car moves forward due to rotational velocity of it's tires. The Matchbox car on a treadmill is an excellent analogy. It does not take any more effort (thrust) for a man to push a Matchbox forward on a moving treadmill than a regular treadmill, assuming negligent friction from the axles and the wheel/treadmill interface. Why? Because the car is moving forward due to thrust (your hand) and not rotational velocity. If it does not require extra effort, when the pilot engages the engines, the plane moves forward and wheels spin faster until friction is broken and the wheels slide.

She flies.

PimpCL23

i say we call mythbusters!

astro

if all you tree goats had just listened to me way back in post #3, this round and round ridiculousness could have been avoided.

SwervinCL

Oh god, here we go again...

PimpCL23

a tree goat.....

that should be a new smiley

IlliNorge

Some of us goats hadn't found our trees yet back in August.

dom

Best explanation.

dom

Yumcha

Well, at least FuriousGeorge will live up to his name...?

Costco

I wonder how fast the plane would be going once it takes off.....

Boeing747

SwervinCL

is300eater

x2

trancemission

@ SwervinCL avatar

thats a keeper....

IlliNorge

Show off. Although, those seats look uncomfortable.

levon1830

Someone told me if this scenario were to be tested with a real plane, the plane would probably implode, turning everyone and everything on board into nothingness. Is this true?

IlliNorge

Hmmm......interesting. Somebody needs to start a new thread to consider this.

SwervinCL

How?

levon1830

I'm not sure, exactly. Something about it creating inconsistencies in the Laws of Physics. One law says it will take off, another says it won't. Apparently in situations like this, the test subject always implodes to destroy the evidence, and to dissuade others from trying to recreate it.

shabaaz

My guess is that it would create a time paradox which would unravel the very fabric of the space time continuum and destroy the entire universe!!

Mizouse

lets do it!