Can an airplane takeoff from a treadmill?

[utexas_61]

where is the "gun to the head" emoticon??

 

[bevo_daddy]

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[Basil Your Face]

 

[Huckleberry]

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[Not that Bob]

Mandingo, I believe I said the same thing you said, but without the head butting thingie.

 

[Statalyzer]

Let me explain to everyone how a treadmill works, since apparently a bunch of you have never worked out before. You set a treadmill to a certain constant speed. Then you begin running in place on it. You have a specific goal in mind that involves running in place, so you automatically, usually without giving too much thought to it, adjust your running speed so that you stay in the center of the treadmill and don't move forward or backward on it. The treadmill does not adjust to you!! If you wanted to, you could speed up and outrun the treadmill, much like you could run up the down escalator if you wanted to.

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[Art Vandelay]

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[madscientist]

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[bobtheking]

So.... What y'all are saying is that the plane..... won't take off?

 

[Basil Your Face]

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[Huckleberry]

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[LonghornSean]

What came first, the chicken or the egg?

 

[bevo_daddy]

So you're saying there's a chance...

 

[Huckleberry]

Here's a step-by-step look:

We have a plane parked on an infinitely long conveyor. Nothing is moving relative to the ground. We are going to try to have the conveyor "match the plane's speed" so that the plane doesn't move. Here we go.

The pilot informs us that he will apply enough thrust to the plane in a single short burst to accelerate the plane to 1mph forward relative to the ground. With this information, we will plan to accelerate the conveyor to 1mph in the opposite direction at exactly the same time. 3...2...1...

Oh ****. The plane is moving 1mph relative to the ground. The conveyor is moving 1mph backward relative to the ground. The only thing we've done is cause the wheels to spin twice as fast, in effect spinning as though the plane is traveling 2mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 2mph relative to our conveyor. Therefore we will speed up the conveyor 2 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 3mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 4mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 4mph relative to our conveyor. Therefore we will speed up the conveyor 4 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 7mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 8mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 8mph relative to our conveyor. Therefore we will speed up the conveyor 8 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 15mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 16mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 16mph relative to our conveyor. Therefore we will speed up the conveyor 16 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 31mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 32mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 32mph relative to our conveyor. Therefore we will speed up the conveyor 32 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 63mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 64mph on normal ground (or a motionless treadmill). What can we do?

I know. The plane is moving 1mph but we know it's moving 64mph relative to our conveyor. Therefore we will speed up the conveyor 64 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 127mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 128mph on normal ground (or a motionless treadmill). What can we do?
I know. The plane is moving 1mph but we know it's moving 128mph relative to our conveyor. Therefore we will speed up the conveyor 128 more miles per hour to make up the difference. Ready, GO!...

Oh ****. The plane is still moving 1mph relative to the ground. The conveyor is now moving 255mph backward relative to the ground. The only thing we've done is cause the wheels to spin faster, now they're spinning as fast as they would if the plane were traveling 256mph on normal ground (or a motionless treadmill). What can we do?

BUT WAIT. Before we can do anything else, the pilot says **** this repetitive ****, applies his thrust, accelerates to 200mph air speed (assuming no wind, this is ground speed of course), and takes off. At which point the wheels are spinning as fast as they would if the plane were moving 456mph on normal ground (or a motionless treadmill).

 

[Basil Your Face]

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[Basil Your Face]

Reading your post above mine, I think I do need to go the extra mile. I KNOW the plane will take off. In order to do so, however, its wheels must spin faster than the conveyor is moving backwards, as you suggest what would happen in the real world. However, if you insert a clause--which you are allowed to do in presenting a HYPOTHETICAL scenario--that the conveyor speed will always match the speed of the wheels, the plane cannot have any forward movement with respect to the ground.

 

[milk_monitor]

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[VacantlyOccupied]

If the plane's wheels are moving forward on the conveyor belt at the equivalent of 200mph and the conveyor belt is moving the opposite direction at the same speed and I'm inside the plane, if I toss a ball straight into the air, will it fall back into my hand or will it go to the back of the plane?

 

[l00p]

If you were in the back of a truck trailer when it crashes and you jumped up the second before it hit a wall and hit the floor a second after, do you get hurt by the concussion of the crash?

 

[Basil Your Face]

I found this on the The Straight Dope, which confirms what I thought was a pretty simple truth:

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[Statalyzer]

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[Huckleberry]

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[rtchorn]

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[mandingo]

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[Huckleberry]

I think the question you guys are basically trying to answer is:

If an airplane is bolted, welded, and tethered in position so that it can't move, can it take off?

Because a treadmill/conveyor will not keep a plane still.

 

[mia1994]

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[Statalyzer]

Mia's last sentence should end the argument once and for all, I don't think there's any way to make the point more succinctly than that.

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[utexas_61]

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[voteforhank]

I think I saw the Coyote do this when he was chasing the Road Runner

 

[netslave]

Here's my explanation in as simple terms as I can make them.
Bob on a treadmill

Bob running @ 10 MPH --- > <-----Treadmill going backward @ 10 MPH = no relative forward movement.

Bob's legs are supporting the weight of Bob.

Bob's legs keep Bob from moving backward.

Bob finds a rope:

Bob grabs hold of a rope and pulls forward

If treadmill can theoretically move infinitely fast, than so can Bob's legs.

Bob's legs moving infinitely fast ---> <------Infinitely fast treadmill = no relative movement. When talking about infinitely fast speeds, they cancel each other out.

Bob's legs are still supporting his weight and keeping him from moving backward.

Bob's arms are pulling on the rope and he eventually moves forward.

Bob's legs moving infinitely fast cancel out the effects of the infinitely fast tread mill.

Bob's arms pulling on rope then allow him to move forward.

**Relate this to an air plane**

If a treadmill can move infinitely fast, than so can the wheels. They cancel each other out.

Then add the air (rope in example) and the engines (Bob's arms) and you should see that the airplane (Bob) will move forward. Sure, the treadmill and wheels will be spinning much faster than designed, but the ground has no effect on the air and vice versa. The air (rope) is what is supplying the "pulling" effect and it will win out. Eventually, the wings would create lift and the wheels would stop touching the treadmill.

Plane takes off and will need new landing gear soon.

EDIT: Now if you want to ask whether or not an airplane can take off during an infinitely fast tail wind, then no, the plane will not take off. It doesn't matter if the plane was going Mach 4 on the ground. If the tail wind matched the plane's speed, lift would never be achieved.

Still more proof the the ground has no (virtually none) effect on the air or the creation of lift.