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/sci/ - Science & Math

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2238178 No.2238178 [Reply] [Original]

>> No.2238187

yes, now go away

>> No.2238183

Yes.

TROLL HARDER

>> No.2238190
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2238190

>>2238183
>>2238187

>yes

>> No.2238189

>>2238183

The wings would snap off, dipshit.

>> No.2238214

>>2238189

Nigger please

>> No.2238224

It would, but then it'd crash because of that damn treadmill.

>> No.2238228

the plane on a treadmill is a classic thought experiment

the plane's thrust comes from the engine and not the wheels, the plane will take off with negligible resistance from the axels


http://en.wikipedia.org/wiki/MythBusters_(2008_season)#Airplane_on_a_Conveyor_Belt

>> No.2238282

>>2238228
Mythbusters did it wrong. Plane obviously does not take off.

>> No.2238420

It's all about the wheel bearing friction.

Bearing friction generates a drag force which drags the plane backwards. The engines generate a thrust which pushes the plane forwards. If the bearings are crappy, the drag force exceeds the thrust force, and the plane goes nowhere. If the bearings are really good (or frictionless), then there is little or no backwards drag force to cancel out the thrust, and the plane takes off.

Calculation of whether or not a real plane can take off from a real treadmill is left as an exercise for the student. Extra credit: Test it with an F-15 or a fully loaded 747.

>> No.2238429

Cannot tell if people are trolling or not...

It will not take off. There is no air going over the wings to create lift.

>> No.2238434

guaranteed 200+ replies

>> No.2238435
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2238435

No, it's a model jet. It'll crash into the dumbass 12 year old that put it on the treadmill and he'll cry until his mother comes and gets him an ice cream. TRIPLESCOOP NIGGAS.

>> No.2238437

The plane will take off. This has been proven numerous times. Anyone who claims otherwise is stupid, a troll, or both.

>> No.2238443

>>2238429
the wheels dont drive the plane. it will take off.

>> No.2238599

>>2238429
There is no airflow, which implies no lift. This is true. I had this problem at first too. What we neglected to account for was the propulsive force of the engine. Iff the engine alone has enough power to lift the plane then it will go up.

>> No.2238688

>>2238599
jet engines create airflow?

>> No.2238692

>>2238443
No one said the wheels drive the plane, you complete assclown.

>> No.2238728

IT DEPENDS ON HOW THE QUESTION IS WORDED. IF THE BELT MATCHES THE FORWARD SPEED OF THE PLANE, THEN THE WHEELS WILL JUST SPIN TWICE AS FAST AS NORMAL AND THE PLANE WILL BE ABLE TO TAKE OFF.

IF THE BELT MATCHES THE ROTATIONAL SPEED OF THE WHEELS SUCH THAT THE WHEELS CAN'T ROLL FORWARD, THEN THE PLANE WON'T BE ABLE TO ROLL FORWARD. BUT BECAUSE THE ENGINE PRODUCES THRUST THAT ACTS TO ACCELERATE THE PLANE, THE PLANE MUST MORE FORWARD. THIS RESULTS IN A PARADOX, THAT CAN ONLY BE SOLVED IF YOU DECIDE F=MA IS NO LONGER VALID IN THIS CRAZY THOUGH EXPERIMENT UNIVERSE. AND IF F=MA ISN'T VALID THEN THE WINGS CAN'T PRODUCE LIFT SO THE PLANE CAN'T FLY.

ANYWAY IT'S ALL PRETTY STUPID BECAUSE IT'S BEEN DONE A BILLION TIMES, BUT MOST PEOPLE ARE TOO DUMB TO FIGURE IT OUT.

>> No.2238773

>>2238728

How does your second scenario imply that F=ma is invalid? The way you wrote it implies that the wheels can rotate at some speed that makes them not able to move forward. I don't know how you think this would happen... The wheels can rotate as fast as they want. They are not the motive force for the plane. The only way the wheels would affect the ability of the plane to take off is rolling friction which shouldn't be considered since the whole question is a thought experiment to begin with and realistically rolling friction is small in comparison to the thrust of the engine. There is no contradiction. Any reasonable interpretation of the problem coincides with the plane taking off.

>> No.2238900

>>2238599

lol the engine is independent of the wheels... therefore no matter how fast the treadmill goes it will not affect the forward motion due to the engines

captacha

trinity gospel

>> No.2238961
File: 32 KB, 600x394, M1A1-Abrams-USMC-01.jpg [View same] [iqdb] [saucenao] [google]
2238961

The plane should not be able to take off if the treadmill keeps it in place as plane itself has no forward momentum and the engine is only working to keep the plane from going backwards.

This reminded me of another fun question from my school days which is pic related. A tank is moving forward at 20 mph. How fast is the tread on the tank moving?

>> No.2238970

>>2238961

The tread is not moving. Obviously.

>> No.2238974

>>2238970
Only the part touching the ground is not moving. The part above is moving at 40 mph. The average velocity of all portions of the tread are 20 mph.

>> No.2238990
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2238990

>anyone who says yes
>anyone who had to think about it for more than 3 seconds

>> No.2239003

Why do people keep asking this question?

No.

There would not be sufficient airflow over the wings to generate lift.

Fuck off.

>> No.2239005

>>2238961

The treadmill will not keep the plane in place. If you enforce static equilibrium on the plane, the friction from the wheels must equal the force from the engine. In every practical case the friction is far exceeded by the force of the engine. The plane will accelerate forward, meaning it WILL take off.

>> No.2239008

>>2239003

You are either a troll, stupid, or both. Try to enforce static equilibrium on the plane. Short of an unrealistic amount of rolling friction, the plane will accelerate and therefore take off.

>> No.2239017

>Easiest way to troll sci
>Works every time.

Yes=Trolled again

No=Trolling again

>> No.2239041

Treadmill isn't plugged in and plane isn't real. So nothing will happen.

>> No.2239043

Mythbusters did it

/thread

>> No.2239079

Yes. The wheels will just move faster. They do not actually propel the plane.

>> No.2239081

>>2238974
The reason I brought up the tank question in the first place is because it's nearly the same question in terms of logic. It's a question of relativity.

In relativity to the tank, the entire tread is also moving at the same speed as the tank, rotating at 20 mph. In relativity to the earth, the bottom of the tread is stationary and the top part is moving at 40 mph. It is not moving at that speed due to compensate for the part that is stationary, it moves at that speed because you add the forward motion of the tank to the forward motion of the tread in relativity to the earth.

The plane will not lift off because there is no forward motion with relativity of the air to generate lift. It's also the same concept of having the wheels on a car off the ground moving at 40 mph and then dropping it into contact to the ground. It will not suddenly start moving at 40 mph because the car when dropped does not have 40 mph of forward momentum. But this is not actually the case.

The trick to all of this is the thrust from the propeller or jet has enough forward momentum to get the plane moving forward. All the treadmill is doing is causing the wheels to spin faster. Once again, relativity.

Happy now?

>> No.2239089

>>2239043
Retard detected. Mythbusters cannot into science.

>> No.2239096

>>2239008
>an unrealistic amount of rolling friction,
There's no such thing as an unrealistic amount of rolling friction. If the speed of the treadmill isn't specified, the rolling friction can be arbitrarily large.

>> No.2239133

>>2239081

See my post:
>>2239005

There does not have to be motion initially for the plane to move and eventually take off. The plane ACCELERATES due to the thrust from the engine/propeller/turbine/whatever.

Check that momentum is conserved:

Initially: Plane is not moving.
Momentum (hereafter denoted as "p") = 0 in the horizontal direction.

Once the treadmill starts moving (or the plane is dropped onto the already moving treadmill, however you want to think of it):

p = 0 since the air moves backward at a certain velocity and the plane moves forward with another velocity.

Momentum is conserved. Now consider acceleration. Without acceleration, the plane can't move from rest as it would necessarily have to accelerate. So there must be some net force on the plane. See my earlier post regarding static equilibrium. You can also confirm the presence of a net force by considering the CHANGE in momentum of the plane. (Force is the time derivative of momentum).

The plane starts with no momentum but ends with forward momentum. Therefore the derivative of momentum for the plane is nonzero. This means there is a net force and therefore acceleration.

The plane will take off. Absolutely.

>>2239096

Yes, you are correct that speed is never specified. However this is a thought experiment. For all PRACTICAL situations, the treadmill would go well below the speed required to inhibit the plane significantly by rolling friction.

>> No.2239214

>>2239133

Well this was me
>>2239081
And I don't know at this point if you are arguing with me or agreeing with me or TL;DR to the end and stopped reading where I said it wouldn't work. At the end I said it would work. The plane still has to move forward at a certain speed to take off. In the case of mythbusters that was 25 mph. The backwards movements from the treadmill of 20 mph will not actually hinder the plane's movement much at all. It will spin the wheels faster, but the forward momentum of the plane is caused by the propeller/jet and the wheels are only there to reduce friction. The explanation that they gave on the show that jets or propellers generate lift is completely bogus though.

>> No.2239249

>>2239214

I don't want to be rude, but I feel you worded your posts poorly which was at least partially the source of this confusion. I'm glad you recognize that the plane would in fact take off. Your posts could have benefited from more technical accuracy however. Your explanation confused momentum with force and some other minor things. I simply misinterpreted this as an attempt to justify a non-takeoff argument which I now realize is not the case. My bad XD

TLDR we both agree the plane takes off and we are both correct!