Why? The engine push the plane forward not by the wheels, the wheels have nothing to do with whether the plane takes off or not, they just spin, if they were locked then yea, it'd hamper the plane from taking off. The faster you make the treadmill go backwards, the faster the tires spin, and that's it, tires are free-spinning, they have no thrust/torque.
Just because they do not propel the plane does not mean the do not affect the plane. Put a toy car, with the best bearing possible, and put it on a level treadmill. Turn the treadmill on. Does the car stay in place or does it go backwards. It goes backwards because the wheels exert rotational friction on the axles.
Only because it has no other forces affecting it, a plane has a force that is not connected to the wheels pushing it forward, the engines push air and thus go forward, so as long as the engines are giving it thrust, the plane accelerates, lest the wheels are locked or there's a mighty strong gust of wind going against it. But make the treadmill go 50x the speed of the plane, wheels will just spin ridiculously fast and plane will still take off like normal
Look at my edit of my first comment for the simple math. You are assuming that the friction due to wheel rotation is negligible, when in fact it is absolutely not. If resistance due to friction is greater than or equal to the opposing force it will NOT move. In this case the friction and resistance is INFINITE where as the force exerted by the planes is extremely finite. EDIT: This guy explains it in irrefutable mathematic terms HERE The simple question is are you looking at it in terms of matching the plane's forward velocity or the wheel's velocity. Mythbusters proved the former, which I have always said would fly. But they cannot ever test or prove the latter, as it is impossible to enact in real world terms.
But in reality it's not since planes take off. You're thinking in the way that the wheels have everything to do with how a plane moves when they don't, the wheels merely provide a way for the plane to slide along the ground until the engines gather enough velocity to push the plane's mass into the sky, the velocity is not gained by the wheels pulling or pushing anything. Edit: Granted that maybe if indeed you did match the rotational speed and all, the momentum/thrust is ever increasing to reach take off velocity, so it doesn't matter how high the friction will pull it since the more velocity the plane gains, the closer it gets to take off, thus wouldn't the weight slowly reduce upon the wheels thus reducing the effect of the friction? It's nearly 5am >.>
Man... Of course the wheels don't push the plane. I can't possibly convince a person if they do not understand what I am saying. It is both mathematically and physically impossible. PERIOD.
Indeed. Although the wheels won't turn without friction (and this does have a minor impact in this 'experiment'), the whole purpose of having wheels on the plane is to reduce the friction between the plane and the ground. Compared to a propeller (which can exert many 000's of pounds of thrust), the friction of the wheels is neglible. Quite correct - as the plane gain velocity, the wings will produce lift which will in turn reduce the friction in the wheels. MaximumShow - Do you really think that you can enter this late into the game with a Eureka!? What makes you think you have the brains to outwit all of us, a TV program with a reputation to maintain, and Sir Isaac Newton? It's fair enough that you don't get it - lots of other people didn't at first (or still dont now), but they had the good grace to try to see the other side.
I think maximum is just trying to mess around and trick people - i once saw a thread about how fans make a pc hotter, because the fan motor makes heat, and the spinning blades get in the way of the case airflow. the guy even gave an example, something like: If a hold a broomstick in front of me, you can reach around it and hit me, but if i'm spinning the broomstick, you will have a hard time trying to hit me... correct maximumshow?
I think you are correct - what Some of the " your all idiots - i'm a genius" posters fail to do is read/comprehend is the original scenario involves a scene thats impossible to replicate & mythbusters pathetic attempt to disprove said scenario is invalid! Until they can stick a 767 on a treadmill that can match the 767's wheel speed perfectly then its a mute point!
Why? Piss off. 1... 2... 3... 4... 5.. Sod it, I'll revert to my initial sentiments: Piss off. The wheels are irrelevant.
Just give up will - anyone who says it doesn't work, having read the arguments and statements put forward in this thread, will never get it. Even if they see it.
Gee this is frustrating. A plane is moving along at say 50m/s (~100mph) (say just over take off speed) down the runway. The wheels say have a circumference of 2m, so they are spinning at 25 revolutions per second (please don't slate my maths in this post it's almost lunch time). So your bearings can cope with 25rps. Lets take a safety factor of say 10x to ensure the bearings don't fail upon landing (eg in an emergency), so they can cope with up to 250rps. Now lets increase the power of the engines so the plane is at 100m/s. Now your wheels are doing 50rps. well that's still in the safety margin, the wheels haven't come off/melted, and the plane will still take off. Now lets put a belt under the wheels with the top surface moving at 50m/s against the movement of the plane, and slow the plane down to 50m/s ground speed. Now the wheels are essentially providing lube to 2 surfaces moving at 100m/s relative to each other. The wheels are still in their load cap, and the plane is still above take off speed, so I put it to them Doubting Thomas's: why won't it take off? The bearings WILL produce a SMALL amount of friction as you'd expect. This would also increase with the higher wheel rotations. The engines will have to be powered up a bit to over come this. That is all. profqwerty
lol.. quality answer. You are right that we can't put a 767 on a conveyor belt, so it may be a *moot* point. Or we could work with science, and clear up the theory. The first step is to understand the problem, which your mentor MaximumShow failed to do: The conveyor belt will adapt to match the velocity of the plane. Not the turning rate of the wheels. Wheels rotate in rpm not mph - if the plane were to move forward at 1mph, the conveyor belt would indeed accelerate to 1pm in the opposing direction. But this wont result in the conveyor belt moving at the speed of light (though I'd pay good money to see that happen) - the wheels would simply rotate faster. Ignoring a very slight effect due to friction in the wheels, this wouldn't alter the speed of the plane at all. as the plane accelerates to a nominal take-off speed of 150mph, the conveyor belt would be also going at 150mph. At this point the poor old wheels will be spinning at a rate of knots, but still it wont significantly effect the plane. Once you realise that the speed of the plane is due to the propeller and not the wheels, it will quickly become clear... Anyway, this was fun while it lasted, but we've done it to death. There is enough explanation in previous posts for anyone with an open mind to get their heads around the issues. So I'm bowing out. Again.
When i fart, the exhaust gas coming out of my a$$ instantly hits like 10mph, but i'm telling you, that's nowhere near the speed of light, or i'd burn my ass everyday. If the plane can hit 1 mph instantly, so can the treadmill, and so can my car, etc...
Why is this even an issue? its like watching the same tv show over and over again. I think its time to turn the tv off.
My god people... Did you read all of my posts? I clearly said that if the conveyor matches the forward velocity of the plane, the plane will easily takeoff. This is what I have always said, and also what mythbusters proved. However, if the conveyor is to match the rotational speed of the wheels it will NEVER take off. This is because the wheels are rotating in the SAME direction as the conveyor, which means one doubles the other, and vice versa, in the attempt to match each other, all the way up to the speed of light in an instant. They are two totally separate scenarios
The resistance on the wheels is cumulative. In everyday life the plane easily has enough force to overcome the resistance involved. This problem is not a real world scenario though, and the resistances involved are infinite. Here is a quote of the ORIGINAL post here on Bit-tech before being edited: This has since been changed to *plane* saying "EDIT: changed 'wheels' to 'plane', now makes more sense". The wording of the problem is key to the outcome.
