Can someone answer this question?

excellent idea. I'd love to see the lengths to which they'd go as proof. man my girlfriend turned that show on saturday morning and I watched it for maybe three hours. I'd never seen it before. those folks are hilarious.
 
I like your way of thinking Marko BUT, the cyclist is propelled by the wheels on the bike and ground speed matters in that case. The plane is propelled by thrust and ground speed is moot.
 
okokok, but see, my jet bike won't work on rollers cause it doesn't spin the wheels. that's my job.



point is, propulsion is inconsequential, as are wheels and resistance. kites fly with no propulsion. with enough air speed, you release the kite and away it goes. air speed drops and the kite falls because it's heavier than air. so are planes.



so now I'm picturing holding a kite by it's string over a moving conveyer. does it fly?
 
that's correct. it's only looking for air speed. so do planes. for all practical purposes, the plane in the experiment is in the same shape as the kite. not the *only* but certainly one of the primary reasons planes fly is air speed over the wings.



after all, this is a plane, not a rocket. physics behind rocket science is a little different.



seems to me that if this experiment were to launch the plane, you'd also be able to hold the plane securely in place while accelerating the engines to flight speed, release it, and suddenly fly. I imagine either of these would be a huge step in aircraft carrier technology, but they're not. I expect my tax dollars go to a military that would exploit this were it actually possible, and I expect the private sector would do the same.



would also be kind of cool if you could launch a private jet from the driveway, but why stop there. let's try a 777 just for fun. but okokok, I know what you're thinking, it might be a little difficult to transport the plane home from the airport to do it again until someone decides we can stop a plane mid-air. technicalities and logistics are always getting in the way.
 
Speaking of Mythbusters, they busted the myth that you get better gas mileage with the tail gate down in a pick up. It actually makes your gas mileage worse. I had an argument with my mechanic from work like all day about this. I even found several other sources that proved it, but he still thinks its true. lol
 
I would suggest that BOTH camps are correct at some point in this scenario. :idea



There is a certain amount of rolling resistance in the airplane's undercarriage. (In any vehicle. You can measure it by determining what slope it takes for the vehile to start to roll on its own. Once it is rolling, this force is somewhat less but that's not really important here). Therefore, as the plane powers up, until the thrust overcomes this rolling resistance, the plane will be influenced greatly by the action of the conveyor. It will move with the conveyor (backwards).



Now, apply sufficient power to just balance the rolling resistance against the moving conveyor and the plane stays stationary, there is no airflow over the wings and there is no flight., Chalk one up for the non-flight group!



However, once you apply more power than is required to overcome the rolling resistance and the plane will start to move forward. The conveyor will try to speed up to counteract this motion however it will not have a significant impact since the resistive force that "ties" it to the moving conveyor is already overcome by the power supplied by the engine.



This rolling resistance is not significantly impacted by the speed of the conveyor; once you get something rolling any increase in speed of the conveyor will only speed up the rotation of the wheels. There is some increase but not important compared to the power of the engine involved. (In cars, it takes more power to go faster not because of increased frictional resistance, but aerodynamic loads.)



Therefore, the plane will be able to add power until it moves forward on the belt, even as the belt itself speeds up, and generate airflow over the wing, lift and hence, flight.

Chalk one up for the flyers. :clap:



The key points to remember are that the plane does not require contact with the ground to apply power (so people on treadmills etc do not duplicate the scenario since you rely on your feet interacting with the belt to propel yourself forward) and that the rolling resistance is not ever increasing. If it were ever increasing, cars would not continue to speed up rolling down hills until the aerodynamic forces overwhelmed the situation.



That's my story and I'm sticking to it. :LOLOL
 
wlhump said:
However, once you apply more power than is required to overcome the rolling resistance and the plane will start to move forward. The conveyor will try to speed up to counteract this motion however it will not have a significant impact since the resistive force that "ties" it to the moving conveyor is already overcome by the power supplied by the engine.



Therefore, the plane will be able to add power until it moves forward on the belt, even as the belt itself speeds up, and generate airflow over the wing, lift and hence, flight.

Chalk one up for the flyers. :clap:
Click to expand...





This is a hypothetical conveyor belt that has every bit as much power as the plane engines can produce. The plane is never moving forward because the conveyor senses forward movement and speeds up in the opposite direction to counteract the forward movement.
 
I do not doubt the power of the conveyor belt. However, it can only act upon the airplane up to the rolling resistance of the tires/wheels. Any power beyond that point, and the tires will just spin.
 
Oops, hit enter too soon.



Afterall, a Saleen S7 has awesume power in comparison to a Yugo, but on ice (very low resistance) I'll bet all that power is basically wasted.
 
Maybe this will help. Look at the conveyer belt as a loss of traction at the wheels BUT the traction isn't essential to the planes forward movement.
 
While I understand the loss of traction scenario, I thought the original question assumed that the tires would grip the same regardless of the conveyor speed. There's too many details left out of the question.
 
wouldnt this be the same as a sea plane taking off in water with the current going against the plane. Think, current going -> at 4mph. Plane going <- at 50mph, needs to get to 60 to take off, wouldent the plane just need to get to 64 to overcome the water? Think about it, seaplanes do not take off with the current all the time.
 
Eliminate the conveyor belt part of it-all that does is counter act what would be the forward motion (obviously causing flight). For me then, the question is- Do the engines alone have enough thrust to propel the plane into flight-no wings involved. Think of it this way-if you had a 1 hp engine on the plane, creating 'x' amount of thrust, it probably wound't fly. But, if you had a 10,000 hp engine creating 10,000 times 'x' thrust, the engines alone would 'fly' irrelevent of the wings.
 
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