Something to think about (warning large images)

[Guest enave]

note to mods: please let me know if this many images violates forum rules. If so, I'll space them out over several posts, or just link to the powerpoint slides here:http://seaofcrisis.com/ext/avsim/airplanetreadmill.ppthttp://seaofcrisis.com/ext/avsim/slide1.gif------------------------------http://seaofcrisis.com/ext/avsim/slide2.gif------------------------------http://seaofcrisis.com/ext/avsim/slide3.gif------------------------------http://seaofcrisis.com/ext/avsim/slide4.gif------------------------------http://seaofcrisis.com/ext/avsim/slide5.gif------------------------------http://seaofcrisis.com/ext/avsim/slide6.gif------------------------------http://seaofcrisis.com/ext/avsim/slide7.gif------------------------------http://seaofcrisis.com/ext/avsim/slide8.gifI'll leave these slides up until my bandwidth is all gone. I'll attach the powerpoint slides to this message so that you can download them if the images don't work.http://forums.avsim.net/user_files/135886.zip

[Guest oyvindhansen]

Great presentation! Entertainting, quirky and, not least, correct.-

[AlaskanFlyboy 7]

Yeah, I don't know why I got so focused on the wheels part, I've taken aerodynamics courses through my college training so I should have known better, but for some reason I was focusing on the wrong forces. In my mind, the aircraft was receiving friction on the wheels, thus adding to net drag. But looking at it, the friction shouldn't be so much that it over powers the prop.----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

[Guest RiddlePilot]

So the original poster is saying that the airplane will fly? I guess so, if you take the route of saying that the transmitter is tied to the airspeed indicator. We're talking about relative motion to the ground here though; in my opinion, the transmitter should be tied to the tires. You say that the airplane is not like a car in that the power applied is not directly transferred to the wheels. I say thats bologna, it may be an indirect transfer, but it does transfer; without power applied, the airplane is not moving forward. If you tie the transmitter to the wheels in the airplane, as soon as power is applied, the wheels will begin to spin, and the treadmill will spin in the opposite direction. We are talking about instantaneous reaction here aren't we?

[Guest enave]

RiddlePilot, would you kindly apply your reasoning to the analogy of a guy wearing roller skates and pulling himself forward by grabbing monkey bars. Thanks.

[AlaskanFlyboy 7]

I'm imagining the friction forces causing his skates to drag a bit behind him, and him having to use more arm strength because of it. This is a little deeper into physics nuances than I really know of though, so it's conjecture.----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

[Guest RiddlePilot]

My reasoning for the guy with the monkey bars...If he is to move forward along the treadmill, the wheel speed of the roller skate wheels has to be greater than the counteracting treadmill speed. If, again, the transmitter is tied to the wheels of the rollerskates, and instantaneous reaction is still present, the speed of the treadmill will always match the speed of the wheels. The person's arms WILL move forward along the monkey bars, but the skates will remain stationary.Like I said before, this whole situation depends on what you choose to say the transmitter is tied to.

[Guest enave]

>> The person's arms WILL move forward along the monkey bars, but the skates will remain stationary.wow. All I can say is just wow.I actually devised a little thought experiment for people who think the way you do. I posted it in the other thread:http://forums.avsim.net/dcboard.php?az=sho...00&mesg_id=2380"Here is another, similar, physics problem for you: there is a butterfly sitting on a set of railroad tracks 20 meters in front of a locomotive. If the locomotive starts moving, the butterfly will flap its wings. The faster the locomotive goes, the faster the butterfly will flap."Applying your logic, the butterfly will stop the train, because that's what you would read into the problem. What I'm trying to make you understand, is that it is inappropriate to read certain things into the problem. It is silly to think that a butterfly could flap its wings hard enough to stop a locomotive, and it's silly to think that a treadmill can stop and airplane.The two problems are exactly the same. They both present a situation with a simple feedback loop. As one thing happens, another thing happens to counteract it. You jump to the conclusion that the counteracting thing is successfull.I give up.

[Guest Philip Olson]

I was under the opinion the the plane would not be able to take off and I still am, sort of. While your display is convincing it does not fit the physics I was thinking of. In fact before you posted this I asked a physics teacher and she agreed that the plane could not take off for lack of airflow over the wings. We actually decided to test this theory to be sure we were right. When we get the details worked out and tested I will post the findings here along with a video. Ok, in my mind I was under the assumption that thrust is the key. You know that an engine produces X amount of thrust so based on your throttle setting the treadmill will move to counter act that amount of thrust instantaneously. Consider this for a moment, place a toy car, like a MatchBox car on a treadmill, turn on the treadmill and the car will be pushed back until it goes off of the treadmill. Now leave the treadmill off but push the car and the car will "drive" off the end. Now if you apply equal force to the car and the treadmill the car will remain in place. Can anyone dispute this? Now the same goes for an aircraft, there is no driving force exerted by the wheels in the toy car nor the aircraft so the result will be the same, equal force and the object remains stationary. If the aircraft remains in place then there is no airflow over the wings, no lift and no take off. The experiment that we will do will involve an RC aircraft but the trick will be to create something that will provide equal force to counter the thrust provided by the airplanes engine. It may take some time for us to properly prepare and conduct this exeperiment but we are going to do it. I admit there is a chance that I might be over looking something and could be wrong but I kind of doubt it at this point. So for now I will have to say that while that the images are interesting and convincing, for me they do not fit what I know of physics so therefore I will test it in the real world. Either way I will be very interested to learn the truth as this is a very interesting puzzle. I will also post here just before we expect to perform the experiment just in case anyone wants to come and witness it. In the mean time wish me luck as this is going to take a lot of work and money! Actually for now the physics teacher will be doing a lot of the work as I am still recovering from my cancer treatments.Philip Olsonhttp://www.precisionmanuals.com/images/forum/supporter.jpg

[michal 44]

>fact before you posted this I asked a physics teacher and she>agreedStrange people are teaching physics these days. If I were you I would be looking for a different school ;). If the teacher got mixed up on complex issues of the Maxwell theory or special relativity I would understand, but not being able to handle elementary Newtonian mechanics circa 1700 it is something else.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

[Guest oyvindhansen]

> The experiment that we will do will involve an RC aircraft>but the trick will be to create something that will provide>equal force to counter the thrust provided by the airplanes>engine.Did you ever consider that it is impossible to build such a machine. You cannot counteract the thrust, because the wheels rotate with negligible friction. If for no other reason, your machinery will break down at some point, as the running speed of the threadmill and wheels would have to approach infinity.-

[victorwest2 0]

The original question made no mention of any transmitter arrangement but only mentioned the fact that the treadmill could match the speed of the aircraft. If the aircraft is moving forward then is the treadmill not moving at a slower speed and therefore invalidating the experiment?

[Guest Vector Victor]

the plane couldn;t take off unless there was airflow over the wings. yes the prop would produce forward thrust keeping the plane stationary on the tread mill. Unless the prop was producting enough air current over the whole surface of the wing no lift would be produced... or not enough. what comes to mind is this: If the thrust was strong enough, the craft (missle i would say) could fly. wings have no purpose in the experiment as i see it. but i think you did a great job explaining this time. i'm simple i like the picturesmark

[Guest]

Yes, anyone who disagrees with your warped ideas knows nothing right?So a teacher who wants to put your theories to the test is a poor teacher...

[mgh 89]

The aircraft will take off, and you need a new physics teacher!Consider the basic physics. If a thrust is applied to the aircraft it must accelerate in the direction of the thrust unless there is an equal and opposite force to stop it. (Newton's Second Law of Motion). There isn't such an equal and opposite force. The only source could be the rolling resistance of the wheels and, in any, realistic aircraft, this will be a fraction of the thrust. The wheels will rotate twice as fast as they would normally. This would absorb a little more rotational energy reducing the acceleration a little. However, the rotational energy in the wheels will be fraction of the energy in the rest of the aircraft so the take off would be only slightly delayed.The analogy of the car on the treadmill doesn't go far enough either. "Now if you apply equal force to the car and the treadmill the car will remain in place. Can anyone dispute this?" No, I don't dispute it, but if you then increase the force of your finger you will push the car forwards.You can't escape Newton's Laws.