Airplane on a treadmill

[scn64]

The Airplane on a Treadmill is a type of physics riddle that usually results in two groups of people taking different sides and calling each other idiots for hours at a time. None the less itÃÆââââ¬Å¡Ã¬Ã¢ââ¬Å¾Ã¢s a fun thought puzzle and worth taking a look at.

 

 

 

The Set Up:

 

 

 

LetÃÆââââ¬Å¡Ã¬Ã¢ââ¬Å¾Ã¢s say that we have a jet airplane (like a 747 for example) trying to take off on a giant runway sized treadmill. The treadmill, which turns in the opposite direction that the plane is facing, is capable of precisely matching the speed of the airplane. HereÃÆââââ¬Å¡Ã¬Ã¢ââ¬Å¾Ã¢s a visual to bring it all together (not drawn to scale obviously )

 

 

 

 

 

 

The Question: Can the airplane take off under these conditions?

[rocketman089]

No.

[destro3979]

i would say its simple

 

once it gets enough speed it would just lift off the tredmill

[Deiophobus]

Solution: turn around.

 

 

 

 

 

side with the other person :wink:

[Make7upu101]

Wouldn't the airplane just stop if the treadmill's going in the opposite direction? Maybe I'm just missing something but the answer seems obvious.

[MPM]

Simply, no.

 

A plane wing has a curve at the top of it. As it passes through air, the air moves faster and a lower pressure area is formed above it.

 

Eventually, the high pressure below the plane pushes the wing(and the plane) up into the low pressure area, and that is when the plane leaves the ground.

 

 

 

If there is a treadmill that matches the opposite speed of the plane, there is no low pressure being formed above the plane. In fact, the low pressure point is below the wings, right above the treadmill.

 

 

 

The plane will never lift off.

[ThurinEthir]

Simple. Turn off the treadmill.

[Stilev]

no, becasue the airplane needs to reach a certain speed in which the the the air pressure below the air plane is higher then the pressure above the plane. since it is on a tredmile, it wouldn't be gaining enough speed in-order to gain the intinal speed for take off.

[scn64]

Simply, no.

 

A plane wing has a curve at the top of it. As it passes through air, the air moves faster and a lower pressure area is formed above it.

 

Eventually, the high pressure below the plane pushes the wing(and the plane) up into the low pressure area, and that is when the plane leaves the ground.

 

 

 

If there is a treadmill that matches the opposite speed of the plane, there is no low pressure being formed above the plane. In fact, the low pressure point is below the wings, right above the treadmill.

 

 

 

The plane will never lift off.

 

 

 

The real question is, will the plane move forward. I know that sounds like a stupid question after I stated that the treadmill matches the speed of the plane, but think about how a jet plane propels itself forward.

[Rebdragon]

It's not really a riddle, more like a simple aerodynamics question :| .

[rocketman089]

The real question is, will the plane move forward. I know that sounds like a stupid question after I stated that the treadmill matches the speed of the plane, but think about how a jet plane propels itself forward.

 

It's not going to lift off without any tangent velocity (which it will obviously never get with a treadmill under it). Also, I thought this was more of a philisophical question, not a matter of physics...

[Tigra00]

No, it won't. The plane would be going from full-speed to dead-stop in the air once it lifted off. It would have to surpass the treadmills ability to keep up with the airplane for it to be able to take off (thus having actual forward movement, not similated forward movement). And that would make the whole thing worthless anyways because then it'd be taking off on normal ground. This is kind of an amatuer physics problems, since it's kinda' obvious. I hope physicists aren't like...Actively debating this...Or something.

[scn64]

The real question is, will the plane move forward. I know that sounds like a stupid question after I stated that the treadmill matches the speed of the plane, but think about how a jet plane propels itself forward.

 

It's not going to lift off without any tangent velocity (which it will obviously never get with a treadmill under it). Also, I thought this was more of a philisophical question, not a matter of physics...

 

 

 

I won't state which side of the argument I stand on...yet. But some would argue that the plane will still move forward because, unlike a car, it does not rely on it's wheels to move forward. It's jets create it's forward motion and the treadmill cannot directly influence the jets.

[rocketman089]

I won't state which side of the argument I stand on...yet. But some would argue that the plane will still move forward because, unlike a car, it does not rely on it's wheels to move forward. It's jets create it's forward motion and the treadmill cannot directly influence the jets.

 

Have you never been on a plane before? They don't just hover and take off, they need to reach a certain speed on land before they can. The means of propulsion make no difference. Not if it was a jet, a rocket, or a regular combustable.

[Evil_Elf]

Yes it would. Thrust is what matters. The speed the plane is going over the ground is irrelevant, the air going over the wings is what's important. In the end the wheels will be spinning twice as fast as they normally would, but the plane would sitll take off.

[rocketman089]

Yes it would. Thrust is what matters. The speed the plane is going over the ground is irrelevant, the air going over the wings is what's important.

 

 

 

There is no air going through the wings. It's going 0 mph forward, why would there be any lift?

[misterxman]

No because the airplane's ability to take off depends on the airflow around the wings. Since the airplane is stationary compared to the air around it, there is no airflow and so no effect on the plane. The only thing that happens is that the wheels are turning.

 

 

 

Just think of yourself on a threadmill. Running on a threadmill, you don't feel the air hitting your face because you are stationary compared to the air. If you were really running outside, the air would be hitting your face because you are moving compared to it.

[scn64]

I won't state which side of the argument I stand on...yet. But some would argue that the plane will still move forward because, unlike a car, it does not rely on it's wheels to move forward. It's jets create it's forward motion and the treadmill cannot directly influence the jets.

 

Have you never been on a plane before? They don't just hover and take off, they need to reach a certain speed on land before they can. The means of propulsion make no difference. Not if it was a jet, a rocket, or a regular combustable.

 

 

 

but since the jets are not pushing against the ground to move would the treadmill have enough effect on the planes movement to stop it? For example, imagine that you're wearing a pair of rollerskates while standing on a moving treadmill. At the same time, a man is standing behind you on the ground, not the treadmill. He holds a wooden stick against your back. Even though the treadmill is spinning in the opposite direction, you still wont move backwards because the stick is not being affected by the treadmill. If the other man were to push the stick forward, you would move forward as well. The argument is that the jets on the plane act as the "stick" since they do not push against the ground to create the planes movement.

[Evil_Elf]

Yes it would. Thrust is what matters. The speed the plane is going over the ground is irrelevant, the air going over the wings is what's important.

 

 

 

There is no air going through the wings. It's going 0 mph forward, why would there be any lift?

 

 

 

Hey, try googling it. I've seen a 50+ page thread on this same thing, there were links from all over the place, and they can explain it to you better than I could.

[rocketman089]

but since the jets are not pushing against the ground to move would the treadmill have enough effect on the planes movement to stop it? For example, imagine that you're wearing a pair of rollerskates while standing on a moving treadmill. At the same time, a man is standing behind you on the ground, not the treadmill. He holds a wooden stick against your back. Even though the treadmill is spinning in the opposite direction, you still wont move backwards because the stick is not being affected by the treadmill. If the other man were to push the stick forward, you would move forward as well. The argument is that the jets on the plane act as the "stick" since they do not push against the ground to create the planes movement.

 

 

 

What?! Look, the plane is not moving forward, thus it is getting no lift. Try to think really hard about it, please.

[scn64]

but since the jets are not pushing against the ground to move would the treadmill have enough effect on the planes movement to stop it? For example, imagine that you're wearing a pair of rollerskates while standing on a moving treadmill. At the same time, a man is standing behind you on the ground, not the treadmill. He holds a wooden stick against your back. Even though the treadmill is spinning in the opposite direction, you still wont move backwards because the stick is not being affected by the treadmill. If the other man were to push the stick forward, you would move forward as well. The argument is that the jets on the plane act as the "stick" since they do not push against the ground to create the planes movement.

 

 

 

What?! Look, the plane is not moving forward, thus it is getting no lift. Try to think really hard about it, please.

 

 

 

I understand that the pane needs to move forward in order to generate lift and take off. I'm saying that the plane might still move forward despite what the treadmill is doing because the jets do not need to push against the ground. The wheels of the plane would spin at the combined speed of the treadmill and the plane.

[rocketman089]

I understand that the pane needs to move forward in order to generate lift and take off. I'm saying that the plane might still move forward despite what the treadmill is doing because the jets do not need to push against the ground. The wheels of the plane would spin at the combined speed of the treadmill and the plane.

 

Like I said it doesn't matter what the means of propulsion is. Equate it to the airplane with it's engines on full blast, but no wheels. It's just sitting there. You're not gunna be able to wish it into the air because there is no lift. It's not going to take off.

[scn64]

I understand that the pane needs to move forward in order to generate lift and take off. I'm saying that the plane might still move forward despite what the treadmill is doing because the jets do not need to push against the ground. The wheels of the plane would spin at the combined speed of the treadmill and the plane.

 

Like I said it doesn't matter what the means of propulsion is. Equate it to the airplane with it's engines on full blast, but no wheels. It's just sitting there. You're not gunna be able to wish it into the air because there is no lift. It's not going to take off.

 

 

 

Going back to my example of a man standing on a treadmill with rollerskates, do you agree that he would move forward if pushed from behind?

[rocketman089]

That analogy has absolutely nothing to do with your question :|. I'm out, it doesn't look like you're going to grasp this.

[misterxman]

scn64, yes the man would move forward if he was pushed from behind. However, your original problem did not include such external forces. If you push the airplane forward so it moves faster than the threadmill can bring it back, then yes eventually with a big enough speed difference the plane would take off (assuming the threadmill has the required length for take off). Still, the plane would be moving when taking off, not standing still.