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File 141324529758.jpg - (57.45KB , 300x300 , threadmill.jpg )
1012 No. 1012 [Edit]
what do you think, /tc/?
Expand all images
>> No. 1047 [Edit]
I never understood why people make a fuzz about this. There's no reason for it to not take off.
It would normally accelerate and take off, no matter how fast the conveyor belt is going. This is because the movement of the plane comes from the jet engines and not from the tyres like on a car.
The plane wouldn't be held in place, it would move forward and take off.

Post edited on 13th Oct 2014, 5:25pm
>> No. 1048 [Edit]
what kinda retard would think it would?
>> No. 1080 [Edit]
>>1048
It would take off. Fact.
>> No. 1103 [Edit]
>>1080
but there is the front part, it would block the wings.
>> No. 1104 [Edit]
>>1080
The treadmill would send it flying back. Fact
>> No. 1105 [Edit]
>>1103
Well you could also say the treadmill on the picture is way too short because the plane would still move forward just like on any other runway. But that's just nit-picking because of the image.
The image is just a simple mock-up that is used to demonstrate this concept in a basic manner by using things the viewer already is familiar with. You shouldn't take it too "literally".

In real life the conveyor belt would have to be really long, just as long as a real runway.

Post edited on 13th Oct 2014, 5:55pm
>> No. 1106 [Edit]
That plane is way too small to actually work and fly. It is probably a model without a working engine.
>> No. 1107 [Edit]
>>1104
Not if the plane engines accelerate at the right speed.
https://www.youtube.com/watch?v=0ul_5DtMLhc
>> No. 1108 [Edit]
It will not take off.
physics.stackexchange.com/questions/32269#32270
>> No. 1110 [Edit]
>>1108
Wrong, the guy in your link said himself it will take off. He only said that it can't take off without moving forward, it has to move forward like in a normal runway to take off and the belt needs to be really long.
>> No. 1111 [Edit]
>>1110
Obviously it will take off if it moves forwards. I always assumed OP's picture to imply that the plane is kept stationary relative to the ground by the motion of the treadmill. Otherwise it's just an obvious question.
>> No. 1112 [Edit]
>>1111
Believe it or not, most people who see this first think the plane would never take off.
>> No. 1113 [Edit]
No, because the wings would hit that front part.
>> No. 1114 [Edit]
>>1113
The picture isn't meant to be taken so literally. I mean, it looks like a complete joke if you take it that way.
>> No. 1119 [Edit]
>>1107
thats a propellor driven piston engine aircraft in your video. the method by which a propellor driven plane flies is entirely different from a jet powered aircraft. jet engine energy output isn't even measured in the same units as piston engines are, they're literally incomparable. you may as well have posted a movie of a flying carpet.
you're clearly not even remotely educated on this topic, i don't see why you're trying to pass yourself off as some sort of expert.
>> No. 1120 [Edit]
>>1119
they both fly because they have wings you genius.
>> No. 1212 [Edit]
I know this isn't meant to be taken seriously, but is it going against a treadmill making it slower, or going backwards, or stationary with respect to the ground?
>> No. 1214 [Edit]
Mythbusters did an episode on this and I don't know why. It's obvious that it will 'cause the engines provide thrust forward by moving air, not by turning the wheels, the wheels freewheel and are just there to hold it up. I can't believe that people are stupid enough to think that this would actually keep it on the ground.
>> No. 1692 [Edit]
>>1214
i disagree
>> No. 1693 [Edit]
>>1114
It looks like a joke even if you don't take it literally.
>> No. 1695 [Edit]
Just so people stop replying to this thread I'm gonna drop a knowledge bomb on you faggots.

It's called "Aerodynamics" and it's the reason airplanes have wings. You see, the wings generate lift by creating a difference in pressure, the shape of wings is such that air underneath is a higher pressure than the air over-top. Because pressure will always seek to reach an equilibrium, the higher pressure air will exert a force on the lower wing surface attempting to mingle with the much lower pressure air running over-top.

It is not the displacement of the engines that causes an airplane to travel upwards. This is idiot-proof when you realize that the engines are permanently mounted sideways, and couldn't possibly produce enough force downwards to generate lift.

The reason the airplane on a treadmill wouldn't work,(so long as the treadmill is rotating at a relative speed above the airplanes minimum take-off speed) is because it's airspeed is insufficient to cause a difference in pressure along the wing surfaces.

There is actually an effect similar to the treadmill mean in real aviation called "Tailwinds"; that is to say when the wind is blowing in a direction parallel to the planes travel, such that the wind is approaching from the rear to the front. It can, at sufficient windspeeds cause an otherwise airborne aircraft at the same engine displacement to stall and fall out of the sky, because the pressure differential under the wings is producing insufficient lift.
>> No. 1756 [Edit]
No, it will not fit between bars
>> No. 1781 [Edit]
File 154835357924.png - (245.52KB , 834x623 , will_helicopter_take_off.png )
1781
>> No. 1783 [Edit]
>>1781
It's obviously a model helicopter with no way of driving the rotor, so no.
>> No. 1905 [Edit]
Of course it will, airplanes are powered by jets which will greatly overcome any friction caused by the runway. The real question is whether it can take off before the wheels explode from the heat. For those not in the know, an airplanes wheels are free rolling and will not provide sufficient friction to prevent the jet engines overpowering them.
>> No. 2354 [Edit]
These sorts of counterintuitive puzzles are great at forcing you to understand physics. Another one I came across which I'm still trying to puzzle out:

https://www.youtube.com/watch?v=k-trDF8Yldc

Which manifests in the "sailing downwind faster than the wind" thing demonstrated by Blackbird: https://en.wikipedia.org/wiki/Blackbird_(land_yacht)
>> No. 2355 [Edit]
It won't, because the wings will crash into the treadmill.
>> No. 2356 [Edit]
>>2354
Ok after some thinking I think I understand this now. There are two main questions to address: why the top wheel counterintuitively spins anti-clockwise despite a force directed from left to right, and why the entire contraption moves to the right faster than the ruler.

The key thing to first observe is that the bottom two wheels aren't uniform in radius. They have an inner and an outer radius (due to the nature of the cotton spoon) which is perhaps more clearly seen in this diagram [1]. This already gives a hint of why it can move to the right faster than the applied force, due to a "gear ratio" effect. However, while the calculations are useful for verifying this quantitatively, it still doesn't give a good intuitive answer, nor does it explain why the top wheel spins anti-clockwise.

The best answer I've seen is courtesy of a post on reddit [2] which I'll quote here for completeness

> For the car to move right, the little wheels must turn clockwise, and the big wheel must turn counter-clockwise. This would give you the impression that the ruler must go left to turn the wheel counter-clockwise. That is true, relative to the car.

>Looking at the construction, one immediately suspects that the size of the wheels is somehow involved. But that isn't quite it. Actually, it is because the big wheel touches the ground wheels on an axle, not the part of the wheel that touches the ground. This creates a situation where the speed the outside of the little wheels move faster (in terms of linear velocity) than the outside of the big wheel.

>So, shifting out point of view to the car, you have a wheel to the ruler, and wheels to the ground, and the wheels are geared such that both surfaces move in the same direction, but the ground moves faster, relative to the car

>So imagine now that the car has a motor, and the ruler is just resting on top. As the car moves right, the ground moves left relative to the car. The ruler moves left relative to the car, but slower than the ground. That means the ruler moves to the right relative to the ground, i.e. the car slowly brings the ruler along behind it.

>If you move the ruler relative to the ground it has to obey the same property, it has to push the car faster than the ruler to obey the property that the ruler is slowly pulled behind the movement of the car.

That is, considering the difference betwen reference frame of the cart vs. the ground explains this phenomenon.


[1] http://web.cs.ucla.edu/~sahai/UnderFaster.pdf
[2] https://old.reddit.com/r/Physics/comments/4ngcqj/somebody_please_help_me_understand_this_i_just/
>> No. 2375 [Edit]
>>2356
This explanation also naturally extends to the "downwind faster than the wind" vehicle Blackbird. It's the same principle, where you derive energy from the relative difference in speed between the air (the ruler) and the ground. There should be no doubt that this is possible in the simple gear example, or you can also think of a lever if you like a static equivalent of how you can increase speed (at the expense of decreased force).

But with a propellor in the vehicle, now the linkage becomes a bit more subtle. You have to consider the propellor not just as a flat disk, but consider the actual blades of the propellor itself which take a helical path. Then the issue of gear ratio is manifested between the forward motion of the vehicle and pitch of the propellor. The fact that the wheels turn the propellor in the direction against the wind, means that vehicle can travel faster than the wind (with respect to the ground) while still maintaining the property that a single propellor blade – importantly accounting for the helical path – is traveling slower than the air surrounding it. The parallels to the simple 3-wheel cart should be clear.
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