MythBusters

[rikadik]

Listen people...

THE PLANE DOES NOT TAKE OFF!

Because after a mishap at a quiz show two goats hijacked a car and parked it on the runway, and have now demanded 0.999... billion dollars in ransom.

 

[CorCentral]

Originally posted by: rikadik
Listen people...

THE PLANE DOES NOT TAKE OFF!

Because after a mishap at a quiz show two goats hijacked a car and parked it on the runway, and have now demanded 0.999... billion dollars in ransom.

QFT/THREAD for the millionth time!

 

[sandorski]

Originally posted by: Venix

Originally posted by: sandorski

Originally posted by: Venix

Originally posted by: sandorski

Originally posted by: Jeff7

Originally posted by: sandorski
Haven't read this thread in approx 1 month, but I'll throw this out there anyway: The Plane doesn't even need to move forward for it to Take Off! Once enough airflow is achieved on the wings, it will simply rise into the air. One problem with that I'm not sure if any aircraft in existence has that kind of thrust. However, if you put a Jet Engine on a Cessna it'd achieve flight faster than you could read this post. Infinitely fast Treadmill or not.

Except that this isn't how a plane works. The engine or propeller just pushes or pulls the plane through the air. The air moving over the wings is what then produces lift, courtesy of the airfoil. You could pull an engineless plane along with a team of pickup trucks, and once they reach its takeoff speed, the plane would take off. Then of course, without any continuing source of thrust to fight wind resistance, it would quickly land again.

Originally posted by: LegendKiller
Give it up. These guys have no concept of jet engine thrust acting upon the air, not the treadmill, pushing the plane. I asked the smartest person I know in physics, he has two masters degrees in nuclear engineering and a MechEng from USC, Summa Cum Laude all of them. He says that anybody who thinks the plane will not take off is mentally deficient.

The best part is, I'm pretty sure that this problem could be easily solved with statics, which I learned during my freshman year. If you want to take it up a notch (bam!), then use dynamics, which I had sophomore year, and account for (minor) things like the rotational inertia of the wheels.

It's like when they tested the myth of a bunch of birds in a truck - if you have 20 birds in an enclosed truck, and they all take off, will the truck get lighter? Obviously not, as the amount of mass within the truck has not changed. People didn't get it, that the weight of the birds in flight is then transferred to the air in the truck, and the air is of course producing a force upon the truck. Birds resting vs birds in flight = same mass in the same volume = same weight. Different weight distribution, but still the same weight.

Wrong. Propellers/Jet engines create the flow of Air over the wings.

Are you actually suggesting a plane flies because the engines push air over the wings? Not because the engines cause the plane to move forward through the air?

to a large extent, especially initially, yes.

edit: see my edit on other post for refinement

Care to explain how the F-16 flies?

Ahh, had an explanation all typed out, then began seeing a problem. A quick Google showed me my error and that Forward Movement was necessary. My bad.

However, a propeller powered aircraft certainly creates some lift even without forward movement. Although not enough to achieve flight.

I see now that I should have just let my monthish ago post stand on its' own and not return to "add" more to the discussion.

The Plane still takes off from the Conveyor regardless!!

 

[rikadik]

Originally posted by: CorCentral

Originally posted by: rikadik
Listen people...

THE PLANE DOES NOT TAKE OFF!

Because after a mishap at a quiz show two goats hijacked a car and parked it on the runway, and have now demanded 0.999... billion dollars in ransom.

QFT/THREAD for the millionth time!

Lol I was joking. :laugh:

 

[Jeff7]

Originally posted by: sandorski
Wrong. Propellers/Jet engines create the flow of Air over the wings.

edit:upon further reflection, it does both, not just one or the other.

I'm glad you experienced enlightenment later. I could have simply posted a picture of a 747 and said "Explain." The 747's engines are mounted under the wings, with the intake in front of the leading edge of those wings, thus it'd be pretty tough for them to push air over the wings.
Hell, how would a glider fly? No engine at all, yet it manages to create its own lift when it's towed behind a powered aircraft, and it continues to move forward once it's cut loose.

 

[ConstipatedVigilante]

Ok, so assuming the plane's engines have an infinite amount of thrust, just as the treadmill can move infinitely fast as the wheels, the plane takes off. The wheels lock up, and as the plane's engines overcome this enormous friction, it moves forward in a cloud of tire smoke and takes off. Right?

I was interpreting the myth from a sort of "clean" perspective before - ie, no wheels locking and stuff, which would make it impossible.

 

[Jeff7]

Originally posted by: ConstipatedVigilante
Ok, so assuming the plane's engines have an infinite amount of thrust, just as the treadmill can move infinitely fast as the wheels, the plane takes off. The wheels lock up, and as the plane's engines overcome this enormous friction, it moves forward in a cloud of tire smoke and takes off. Right?

I was interpreting the myth from a sort of "clean" perspective before - ie, no wheels locking and stuff, which would make it impossible.

Nah, I addressed this in the previous thread. Once the treadmill reaches the speed of light, C, it turns into a huge blast of gamma radiation, vaporizing most of the airplane, and sending the remaining shards flying away at extremely high speeds. Thus, the plane, in some form, takes off.

 

[sandorski]

Originally posted by: Jeff7

Originally posted by: sandorski
Wrong. Propellers/Jet engines create the flow of Air over the wings.

edit:upon further reflection, it does both, not just one or the other.

I'm glad you experienced enlightenment later. I could have simply posted a picture of a 747 and said "Explain." The 747's engines are mounted under the wings, with the intake in front of the leading edge of those wings, thus it'd be pretty tough for them to push air over the wings.
Hell, how would a glider fly? No engine at all, yet it manages to create its own lift when it's towed behind a powered aircraft, and it continues to move forward once it's cut loose.

Well, the Air doesn't need to necessarily flow "over" the wings, kinda. If enough Air flows under the wings Lift can also be achieved, according to one theory anyway. There seems to be some disagreement as to which is more important, the Air flowing under the wings or the air flowing over the top of the wings. Generally speaking though, when one says "flow over the wings" they don't necessarily mean above. What they mean is "across the surface".

 

[rikadik]

Originally posted by: sandorski

Originally posted by: Jeff7

Originally posted by: sandorski
Wrong. Propellers/Jet engines create the flow of Air over the wings.

edit:upon further reflection, it does both, not just one or the other.

I'm glad you experienced enlightenment later. I could have simply posted a picture of a 747 and said "Explain." The 747's engines are mounted under the wings, with the intake in front of the leading edge of those wings, thus it'd be pretty tough for them to push air over the wings.
Hell, how would a glider fly? No engine at all, yet it manages to create its own lift when it's towed behind a powered aircraft, and it continues to move forward once it's cut loose.

Well, the Air doesn't need to necessarily flow "over" the wings, kinda. If enough Air flows under the wings Lift can also be achieved, according to one theory anyway. There seems to be some disagreement as to which is more important, the Air flowing under the wings or the air flowing over the top of the wings. Generally speaking though, when one says "flow over the wings" they don't necessarily mean above. What they mean is "across the surface".

It has to be flowing over and under the wings, but at different speeds.

 

[LegendKiller]

Originally posted by: sandorski

Originally posted by: Jeff7

Originally posted by: sandorski
Haven't read this thread in approx 1 month, but I'll throw this out there anyway: The Plane doesn't even need to move forward for it to Take Off! Once enough airflow is achieved on the wings, it will simply rise into the air. One problem with that I'm not sure if any aircraft in existence has that kind of thrust. However, if you put a Jet Engine on a Cessna it'd achieve flight faster than you could read this post. Infinitely fast Treadmill or not.

Except that this isn't how a plane works. The engine or propeller just pushes or pulls the plane through the air. The air moving over the wings is what then produces lift, courtesy of the airfoil. You could pull an engineless plane along with a team of pickup trucks, and once they reach its takeoff speed, the plane would take off. Then of course, without any continuing source of thrust to fight wind resistance, it would quickly land again.

Originally posted by: LegendKiller
Give it up. These guys have no concept of jet engine thrust acting upon the air, not the treadmill, pushing the plane. I asked the smartest person I know in physics, he has two masters degrees in nuclear engineering and a MechEng from USC, Summa Cum Laude all of them. He says that anybody who thinks the plane will not take off is mentally deficient.

The best part is, I'm pretty sure that this problem could be easily solved with statics, which I learned during my freshman year. If you want to take it up a notch (bam!), then use dynamics, which I had sophomore year, and account for (minor) things like the rotational inertia of the wheels.

It's like when they tested the myth of a bunch of birds in a truck - if you have 20 birds in an enclosed truck, and they all take off, will the truck get lighter? Obviously not, as the amount of mass within the truck has not changed. People didn't get it, that the weight of the birds in flight is then transferred to the air in the truck, and the air is of course producing a force upon the truck. Birds resting vs birds in flight = same mass in the same volume = same weight. Different weight distribution, but still the same weight.

Wrong. Propellers/Jet engines create the flow of Air over the wings.

edit:upon further reflection, it does both, not just one or the other.

Airflow over the wings are caused by the thrust of the engine pushing/pulling the plane forward by acting upon **air**, not the ground, displacing the plane's mass from one place in ********airspace******* to another. The thrust occurs regardless of whether a wing is there or not, see rockets. It's the simple physics of an action will have an equal and opposite reaction. Airflow over the wings is the byproduct of that displacement.

Since the wheels are free standing and free moving, they are completely independent of the thrust of the engine. They have no bearing on moving forward and prevent the only force that can significantly impede the plane, friction.

Since the plane's mass is acting upon airspace, is displaced through airspace, and the wheels are independent that means the plane's mass cannot be impeded by any ground based unfluence, including a treadmill.

To think otherwise is the hight of ignorance. Despite the one dude's image of intelligence by using formulas, he lacks simple logic.

 

[sandorski]

Originally posted by: LegendKiller

Originally posted by: sandorski

Originally posted by: Jeff7

Originally posted by: sandorski
Haven't read this thread in approx 1 month, but I'll throw this out there anyway: The Plane doesn't even need to move forward for it to Take Off! Once enough airflow is achieved on the wings, it will simply rise into the air. One problem with that I'm not sure if any aircraft in existence has that kind of thrust. However, if you put a Jet Engine on a Cessna it'd achieve flight faster than you could read this post. Infinitely fast Treadmill or not.

Except that this isn't how a plane works. The engine or propeller just pushes or pulls the plane through the air. The air moving over the wings is what then produces lift, courtesy of the airfoil. You could pull an engineless plane along with a team of pickup trucks, and once they reach its takeoff speed, the plane would take off. Then of course, without any continuing source of thrust to fight wind resistance, it would quickly land again.

Originally posted by: LegendKiller
Give it up. These guys have no concept of jet engine thrust acting upon the air, not the treadmill, pushing the plane. I asked the smartest person I know in physics, he has two masters degrees in nuclear engineering and a MechEng from USC, Summa Cum Laude all of them. He says that anybody who thinks the plane will not take off is mentally deficient.

The best part is, I'm pretty sure that this problem could be easily solved with statics, which I learned during my freshman year. If you want to take it up a notch (bam!), then use dynamics, which I had sophomore year, and account for (minor) things like the rotational inertia of the wheels.

It's like when they tested the myth of a bunch of birds in a truck - if you have 20 birds in an enclosed truck, and they all take off, will the truck get lighter? Obviously not, as the amount of mass within the truck has not changed. People didn't get it, that the weight of the birds in flight is then transferred to the air in the truck, and the air is of course producing a force upon the truck. Birds resting vs birds in flight = same mass in the same volume = same weight. Different weight distribution, but still the same weight.

Wrong. Propellers/Jet engines create the flow of Air over the wings.

edit:upon further reflection, it does both, not just one or the other.

Airflow over the wings are caused by the thrust of the engine pushing/pulling the plane forward by acting upon **air**, not the ground, displacing the plane's mass from one place in ********airspace******* to another. The thrust occurs regardless of whether a wing is there or not, see rockets. It's the simple physics of an action will have an equal and opposite reaction. Airflow over the wings is the byproduct of that displacement.

Since the wheels are free standing and free moving, they are completely independent of the thrust of the engine. They have no bearing on moving forward and prevent the only force that can significantly impede the plane, friction.

Since the plane's mass is acting upon airspace, is displaced through airspace, and the wheels are independent that means the plane's mass cannot be impeded by any ground based unfluence, including a treadmill.

To think otherwise is the hight of ignorance. Despite the one dude's image of intelligence by using formulas, he lacks simple logic.

Already corrected through other posts...I'll put a warning on that though.

 

[sandorski]

nmd

 

[Eeezee]

The most important aspect of this problem is that the friction between the plane and the treadmill reaches a maximum. The plane's engine just has to overcome this maximum value, and it will begin accelerating forward.

The original version of the problem that I read posed the situation differently; the treadmill could exert infinite friction on the plane (ie let's say there's a small brick wall in front of the wheels preventing the plane from ever moving forward). In this case, you'd need an extremely powerful engine in order for the plane to take off, and the engine would have to be pushing air over the wings (as opposed to some plane designs where the engine just creates thrust forward and pushes the air out the back).

In both cases, it is still possible for the plane to take off. In case A, the plane will be accelerating along the treadmill no matter how fast the treadmill is going, therefore it's as though the plane were moving along an ordinary runway. In case B, the plane is constrained such that it can't move (the treadmill is magical and doesn't obey real world physics, or imagine a normal runway but the plane is being held in place such that it could only move into the air or not move at all). In case B, you just need to push enough air over the wings to get lift, but it's certainly possible given a light plane and a powerful engine.

 

[CorCentral]

Originally posted by: rikadik

Originally posted by: CorCentral

Originally posted by: rikadik
Listen people...

THE PLANE DOES NOT TAKE OFF!

Because after a mishap at a quiz show two goats hijacked a car and parked it on the runway, and have now demanded 0.999... billion dollars in ransom.

QFT/THREAD for the millionth time!

Lol I was joking. :laugh:

I know you were joking about the Goats, I should've quoted /bolded just that.

But I still don't get the goats! I heard they either wanted the money, or women. Not sure of the conversion rate on that???? .111billion= 1 woman?...... 9 women would be a steal if I were a goat!

EDIT: I did BOLDEN the text, you just misread

 

[smack Down]

Originally posted by: waggy

Originally posted by: sdifox

Originally posted by: smack Down

Originally posted by: DanTMWTMP
I've never seen a more dense person who refuses to thoroughly read anything than Jandrews.

The argument isn't about wind going over the wings. It's about the plane moving foward in relation to a point outside of the threadmill/plane model. In relation to this point, the plane moves forward as if the treadmill is nonexistent. Numerous youtube videos already show that the plane moves foward. Engines act on the air, not on the ground.

A Car WILL stay stationary
A plane will not.

I have no idea why you are so stupidly dense not to realize this utterly simple riddle.

You are completely wrong. A Car and plane will behave identical on a treadmill.

AS for the physics lets pretend that we have two cars that have the same mass(m), same moment of inertia(i), and no friction. For the sake of simplicity lets take the acceleration at 1 m/s/s

On a road do you agree that they would reach a speed of 1 m/s after one second of driving? and both have the same amount of kinetic energy? 1 * m + 1 * i

Ok now lets put our two cars on the same treadmill. Your theory is the the rocket car will still accelerate at 1 m/s/s (or some other value greater then zero) and the engine car will accelerate at 0 m/s/s (that is stay in place). Correct? Additional you claim that the treadmill will be going backwards at a minimum of 1 m/s/s (In reality it would be going faster then this. The speed depends on the mass of the car. 1 m/s/s is only true with a car of zero mass.)

The rocket car energy is 1 * m + i * (1 + Vtreadmill)^2.
The normal car has an energy is 0 *m + i * Vtreadmill^2

Remember that in the 1 second on the road they had the same energy and now the rocket car has much more energy when both are required to be equal and equal to the original 1 * m + 1 * i. There is no way a plane can behave differently then the car.

err, we are talking about how the energy is used. car torques the wheels to move forward, plane does not torque the wheel to move forward. Otherwise we would have no airplanes!

good luck. smackdown is a idiot. anyone who thinks a car and airplane behave identical is a idiot.
IF they did operate the same we all would have flying cars by now!

Why is it when you can't understand simple physics you assume everyone else is an idiot. Just explain where the additional energy came from for the plane to act differently?

 

[smack Down]

Originally posted by: sdifox

Originally posted by: smack Down

Originally posted by: DanTMWTMP
I've never seen a more dense person who refuses to thoroughly read anything than Jandrews.

The argument isn't about wind going over the wings. It's about the plane moving foward in relation to a point outside of the threadmill/plane model. In relation to this point, the plane moves forward as if the treadmill is nonexistent. Numerous youtube videos already show that the plane moves foward. Engines act on the air, not on the ground.

A Car WILL stay stationary
A plane will not.

I have no idea why you are so stupidly dense not to realize this utterly simple riddle.

You are completely wrong. A Car and plane will behave identical on a treadmill.

AS for the physics lets pretend that we have two cars that have the same mass(m), same moment of inertia(i), and no friction. For the sake of simplicity lets take the acceleration at 1 m/s/s

On a road do you agree that they would reach a speed of 1 m/s after one second of driving? and both have the same amount of kinetic energy? 1 * m + 1 * i

Ok now lets put our two cars on the same treadmill. Your theory is the the rocket car will still accelerate at 1 m/s/s (or some other value greater then zero) and the engine car will accelerate at 0 m/s/s (that is stay in place). Correct? Additional you claim that the treadmill will be going backwards at a minimum of 1 m/s/s (In reality it would be going faster then this. The speed depends on the mass of the car. 1 m/s/s is only true with a car of zero mass.)

The rocket car energy is 1 * m + i * (1 + Vtreadmill)^2.
The normal car has an energy is 0 *m + i * Vtreadmill^2

Remember that in the 1 second on the road they had the same energy and now the rocket car has much more energy when both are required to be equal and equal to the original 1 * m + 1 * i. There is no way a plane can behave differently then the car.

err, we are talking about how the energy is used. car torques the wheels to move forward, plane does not torque the wheel to move forward. Otherwise we would have no airplanes!

Energy isn't used it is converted from one form to another. Just explain how the plane gets the additional energy.

 

[Jeff7]

Originally posted by: sandorski
Well, the Air doesn't need to necessarily flow "over" the wings, kinda. If enough Air flows under the wings Lift can also be achieved, according to one theory anyway. There seems to be some disagreement as to which is more important, the Air flowing under the wings or the air flowing over the top of the wings. Generally speaking though, when one says "flow over the wings" they don't necessarily mean above. What they mean is "across the surface".

The more rapidly air flows, the lower its pressure. Look up "airfoil" - the top of the wing is curved, while the bottom is relatively flat. When the wing passes through air, the air on the bottom can pass straight across. But on the top, the air must flow over the curve - it needs to cross over more surface area, so it has to move faster. Result: higher pressure on the bottom than on top. Next result: Lift.
For air flowing only underneath the wings, the pressure under the wings would then be lower than that above, and so the higher pressure above would push down on the wings, keeping the plane firmly planted on the ground.


Welcome to Mythbusters...

 

[Maximilian]

Well its about friggin time lol, this crap has been going on for ages. I personally think it will crash but thats just me.

 

[sandorski]

Originally posted by: Jeff7

Originally posted by: sandorski
Well, the Air doesn't need to necessarily flow "over" the wings, kinda. If enough Air flows under the wings Lift can also be achieved, according to one theory anyway. There seems to be some disagreement as to which is more important, the Air flowing under the wings or the air flowing over the top of the wings. Generally speaking though, when one says "flow over the wings" they don't necessarily mean above. What they mean is "across the surface".

The more rapidly air flows, the lower its pressure. Look up "airfoil" - the top of the wing is curved, while the bottom is relatively flat. When the wing passes through air, the air on the bottom can pass straight across. But on the top, the air must flow over the curve - it needs to cross over more surface area, so it has to move faster. Result: higher pressure on the bottom than on top. Next result: Lift.
For air flowing only underneath the wings, the pressure under the wings would then be lower than that above, and so the higher pressure above would push down on the wings, keeping the plane firmly planted on the ground.


Welcome to Mythbusters...

Even Physicists disagree on this, so I'm not gonna get into this debate. Except to say: There are 2 varying Pressures involed. One is lower, the other is higher. Which causes Lift or what the exact relationship between them is, is not fully understood.

 

[BeauJangles]

Originally posted by: smack Down

Energy isn't used it is converted from one form to another. Just explain how the plane gets the additional energy.

Regardless of energy, a plane and a car do not behave identically on a treadmill. Look through this thread - watch the youtube videos if you really don't believe us, but the freaking plane takes off.

 

[Jeff7]

Originally posted by: sandorski
Even Physicists disagree on this, so I'm not gonna get into this debate. Except to say: There are 2 varying Pressures involed. One is lower, the other is higher. Which causes Lift or what the exact relationship between them is, is not fully understood.

Really? Where is it debated? At least at subsonic speeds, I thought it was pretty well figured. Supersonic speeds, then things get a bit weird.

Link

Maybe the very basics of an airfoil are understood, but the exact understanding of the airflow on a very small level is the problem. Or if you want exact calculations, then you might have to factor in that oh-so-fun phenomenon: turbulence. Good old chaotic, inherently unpredictable, turbulence.


In any event, on a standard passenger jet or single-engine plane, it's the wing shape that produces lift when air flows over it. In a plane like a Cessna, yes, the propeller happens to push air over the wings, but not nearly enough to take off - otherwise, a Cessna would be a vertical-takeoff aircraft. It's the motion of the plane through the air, with sufficient speed, that lets the airfoil work its magic.

 

[ric0chet06]

anyone want to bet money on this? it wont take off

 

[Jeff7]

I wouldn't bet any money on results coming from Mythbusters. They're about entertainment, not accuracy. They've got too strict a budget (money, resources, and people), and too little time, in order to truly run proper tests with sufficient quantity to get a good statistical model.

 

[Cold Steel]

This is Mythbusters after all. So, one of two things will happen.
1. They will place large amounts of explosives in the plane and/or "treadmill" and blow the thing to hell.
2. They will blow the plane to hell with a minigun.

After all, these are the same people who "proved" that you get wetter by running through rain than by walking.

Oh, and the plane will take off, but maybe not on Mythbusters.

 

[smack Down]

Originally posted by: BlinderBomber

Originally posted by: smack Down

Energy isn't used it is converted from one form to another. Just explain how the plane gets the additional energy.

Regardless of energy, a plane and a car do not behave identically on a treadmill. Look through this thread - watch the youtube videos if you really don't believe us, but the freaking plane takes off.

Right lets ignore the physics and look at a video. Want me to post a video of a pound of fathers falling and a pound of lead as proof that gravity affects them differently?