Think your smart?
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parchisi
New Member
Imagine the airplane sitting still, wheels spinning on the treadmill. If you look at one spot on the outside of the tire, and one spot on the treadmill, they are moving at the same speed. But when you push the airplane forward, you are increasing the wheel's speed while the speed of the treadmill remains the same. So you end up with
(wheel speed) = (treadmill speed) + (speed resultant from forward motion).
So therefore, no matter how fast the treadmill goes, it won't be able to match the speed of the wheel when the plane is in motion. The only time the speeds can be equal (like said in the original question), is when the plane is motionless. But like I said before, there is actually nothing to keep the plane from moving forward so the question gives an impossible scenario. Hope that made more sense.
(wheel speed) = (treadmill speed) + (speed resultant from forward motion).
So therefore, no matter how fast the treadmill goes, it won't be able to match the speed of the wheel when the plane is in motion. The only time the speeds can be equal (like said in the original question), is when the plane is motionless. But like I said before, there is actually nothing to keep the plane from moving forward so the question gives an impossible scenario. Hope that made more sense.
parchisi
New Member
Low-5.0 said:
I think we're missing what I was trying to say. I'll continue to use your analogy. The tires and treadmill are going at 30 mph, and you push the bike forward at 1mph, so then the wheels are going 31mph. You then say that the treadmill speed increases to match the 31mph, but when you increase the speed of the treadmill 1mph, that in turn also increases the speed of the wheel by 1mph, so that the wheel is now turning at 32mph and the treadmill is goign at 31mph. It is impossible to make up that 1mph difference in speeds, and the question specifically says that the speed of the wheel and the speed of the treadmill must remain the same. This is all assuming that you continue to push the bike at 1mph and you do not stop. I'm not saying that the plane won't take off, but it won't take off without violating one requirement of the scenario.
blksn955.o
Founding Member
GRGT1994 said:
I was in ref. to how the whole treadmill was even designed to work. As the loads of an entire plane on a treadmill in order for the treadmill to even move still and not be "locked up" from the mass of the plane. This super treadmill and the factors in its controle over the tires is why I say its a BS question.
someone posted that if you have the breaks on the wheels it will push the plane and take off. I would bet the tires would pop/cause the flat spot to become lethal before the plane gets airborn and crashes at the end of the runway. All that would be needed is one set to go then all hell would break loose.
"The conveyor belt spins in reverse the exact same speed as the wheels at any given time." If you focus on the any given time, since this is a hyp. question in the first place....does it mean any as in absolute. It brings your focus on the tires on purpose. This is why I say its a loaded question that is not possible to test as all information is not given to make a real world test. The question does not say any outside force can overpower the conveyor or break its magic grip on the wheels. IF the wheels will just spin 2x's as fast why will the conveyer not spin 2x's as fast if it spins in reverse at the exact same speed at any given time?
Its a good theory both ways math can prove its side and logic has a point as well.
bottom line is we cannot test this and make it repeatable on the conveyor that does not exist and one that will prob. never exist.
parchisi said:
I think you have something here. The question did state
Stangster5.0 said:
And you are right that that cannot happen once the plane moves forward. This seems to be part of what troubles others here. Since this is an old question (one that has even been posted on StangNet before), I didn't focus on that precise language because I knew in the back of my head what the right hypothetical was supposed to be. But I can see how the hypo as presented is flawed.
I think the proper way to pose the hypothetical is not to say that the conveyor spins at the "exact same speed," but merely to point out that it moves backward as the wheels spin forward (note, in my phrasing there isn't the troublesome speed match). Interesting how such a seemingly benign mistake in phrasing causes so much trouble.
BlueOvalStangGT
Active Member
95CobraMike
Active Member
no wind = no lift....
the shape of the wings make the plane fly.... flat on the bottom and curved on top, the air moving over the wing is moving slower than the air going under the wing causing an area of low pressure on the top
also the more the thrusters thrust, the faster the wheels would have spun, but the conveyer belt speeds up to accomidate for that so there will not be any air passing over or under the wings
the shape of the wings make the plane fly.... flat on the bottom and curved on top, the air moving over the wing is moving slower than the air going under the wing causing an area of low pressure on the top
also the more the thrusters thrust, the faster the wheels would have spun, but the conveyer belt speeds up to accomidate for that so there will not be any air passing over or under the wings
Swarzkopf
Member
Nothing can move faster than the speed of light. Light travels only at the speed of light and cannot move faster.
Okay, lets say a guy in outerspace points two flashlights at opposite ends of the universe and turns them on. The light beams are shining away from each other.
Relative to one another, are the light beams moving faster than the speed of light? They can't be, because nothing can move faster than the speed of light, right? Discuss.
Okay, lets say a guy in outerspace points two flashlights at opposite ends of the universe and turns them on. The light beams are shining away from each other.
Relative to one another, are the light beams moving faster than the speed of light? They can't be, because nothing can move faster than the speed of light, right? Discuss.
I did not stay at a holiday inn express last night, but I am a pilot (helicopters, but the laws of aerodynamics still apply to airplanes). The original question stated that the conveyor belt would spin as fast as the wheels. Therefore, as others have said, no forward movement= no airflow over the wings= no lift.
Chuck
Chuck
1105
I AM the random post master...bow down
JT, don't give up on your theory... You're right. There is no way the plane will be able to take off unless it drags the wheels on the ground so they rotate at the same speed of the conveyor.
The plane relies on its wheels to move along the ground. There's no getting around that not until it gets into the air.
No matter how fast the plane is moving, its still moving on the ground (until airborne) with the wheels roating at a certain speed, and if the speed of the conveyor is matching the speed of the wheels there will be no absolute x movement = not taking off.
Forget about friction, speed, and everything else. If the speed of the wheels and the conveyor are exactly the same, it won't be moving anywhere. And since the plane has to rely on its wheels to move along the ground, it will not be moving anywhere.
The plane relies on its wheels to move along the ground. There's no getting around that not until it gets into the air.
No matter how fast the plane is moving, its still moving on the ground (until airborne) with the wheels roating at a certain speed, and if the speed of the conveyor is matching the speed of the wheels there will be no absolute x movement = not taking off.
Forget about friction, speed, and everything else. If the speed of the wheels and the conveyor are exactly the same, it won't be moving anywhere. And since the plane has to rely on its wheels to move along the ground, it will not be moving anywhere.
SWYZ721
Member
If the plane doesn't move forward then no lift can be created, this really isn't that hard guys.
Holy confusion Batman. It's as if the past 2 douzen or so posts didn't happen.
How bout this, since we all can prolly agree that the original post is wrongly stated, let's use the following as the actual question.
Could a plane take off if it were sitting on a frictionless surface (for example ice, water, or a super large conveyor that spins freely in response to any forces sent from the planes wheels)?
That is what the original post was supposed to say. Now discuss.
How bout this, since we all can prolly agree that the original post is wrongly stated, let's use the following as the actual question.
Could a plane take off if it were sitting on a frictionless surface (for example ice, water, or a super large conveyor that spins freely in response to any forces sent from the planes wheels)?
That is what the original post was supposed to say. Now discuss.
MysteryMachine
Active Member
I don't give a **** about the damn plane. But what the hell does crux mean?
I'm not smart I know lol
I'm not smart I know lol
Ok... Now for anybody that doesn't know me, I am a pilot myself, and finishing up my BS in Aviation Operations, so let me give you all a little insight into the world of flight, as it pertains to this problem....
I completely agree with Low-5.0, mo_dingo, and the others that have a grasp on this concept. What people need to realize is that an aircraft uses a propeller or engine nozzle to transfer the work done by the engine to the air to propel you forward. In contrast, your car uses tires to transfer the work done by your engine to the ground to propel you forward. HUGE difference, and it doesn't matter what anyone says about the conveyer belt matching the speed of the tire because IT IS IRRELEVANT TO AIRCRAFT PROPULSION. The belt could spin the tires backward at 50,000 rpm, but what matters is how the plane moves through the air. The propeller cuts through the air, providing a forward thrust that, unless is completely counteracted, WILL pull the plane forward.
I think where people are getting hung up is that the aircraft uses its wheels to move it forward, or that there is some relationship between how fast the ground is moving/rotation of the tires to the airplane itself. You guys that used the treadmill analogy had it perfect, so let me add to it. Instead of having someone next to the bike, pushing it forward, attach a winch infront of the treadmill, with the cable fixed to the front of the bike. Now it doesn't make a difference if the treadmill and tires are spinning at 10 rpm or 10,000 rpm, as long as it is not going anywhere. Now are there people out there that think that by retracting the cable into the winch, and therefore pulling the bike forward (much like a propeller or jet engine would do in the case of aviation) that the bike would still not move forward???
In conclusion, propulsion in aviation has absolutely no bearing on what the ground is doing... AIR IS THE MEDIUM for flight, GROUND IS THE MEDIUM for driving... Any questions??
I completely agree with Low-5.0, mo_dingo, and the others that have a grasp on this concept. What people need to realize is that an aircraft uses a propeller or engine nozzle to transfer the work done by the engine to the air to propel you forward. In contrast, your car uses tires to transfer the work done by your engine to the ground to propel you forward. HUGE difference, and it doesn't matter what anyone says about the conveyer belt matching the speed of the tire because IT IS IRRELEVANT TO AIRCRAFT PROPULSION. The belt could spin the tires backward at 50,000 rpm, but what matters is how the plane moves through the air. The propeller cuts through the air, providing a forward thrust that, unless is completely counteracted, WILL pull the plane forward.
I think where people are getting hung up is that the aircraft uses its wheels to move it forward, or that there is some relationship between how fast the ground is moving/rotation of the tires to the airplane itself. You guys that used the treadmill analogy had it perfect, so let me add to it. Instead of having someone next to the bike, pushing it forward, attach a winch infront of the treadmill, with the cable fixed to the front of the bike. Now it doesn't make a difference if the treadmill and tires are spinning at 10 rpm or 10,000 rpm, as long as it is not going anywhere. Now are there people out there that think that by retracting the cable into the winch, and therefore pulling the bike forward (much like a propeller or jet engine would do in the case of aviation) that the bike would still not move forward???
In conclusion, propulsion in aviation has absolutely no bearing on what the ground is doing... AIR IS THE MEDIUM for flight, GROUND IS THE MEDIUM for driving... Any questions??
MysteryMachine
Active Member
so what your a pilot what do you know94GTPilot said:Ok... Now for anybody that doesn't know me, I am a pilot myself, and finishing up my BS in Aviation Operations, so let me give you all a little insight into the world of flight, as it pertains to this problem....
I completely agree with Low-5.0, mo_dingo, and the others that have a grasp on this concept. What people need to realize is that an aircraft uses a propeller or engine nozzle to transfer the work done by the engine to the air to propel you forward. In contrast, your car uses tires to transfer the work done by your engine to the ground to propel you forward. HUGE difference, and it doesn't matter what anyone says about the conveyer belt matching the speed of the tire because IT IS IRRELEVANT TO AIRCRAFT PROPULSION. The belt could spin the tires backward at 50,000 rpm, but what matters is how the plane moves through the air. The propeller cuts through the air, providing a forward thrust that, unless is completely counteracted, WILL pull the plane forward.
I think where people are getting hung up is that the aircraft uses its wheels to move it forward, or that there is some relationship between how fast the ground is moving/rotation of the tires to the airplane itself. You guys that used the treadmill analogy had it perfect, so let me add to it. Instead of having someone next to the bike, pushing it forward, attach a winch infront of the treadmill, with the cable fixed to the front of the bike. Now it doesn't make a difference if the treadmill and tires are spinning at 10 rpm or 10,000 rpm, as long as it is not going anywhere. Now are there people out there that think that by retracting the cable into the winch, and therefore pulling the bike forward (much like a propeller or jet engine would do in the case of aviation) that the bike would still not move forward???
In conclusion, propulsion in aviation has absolutely no bearing on what the ground is doing... AIR IS THE MEDIUM for flight, GROUND IS THE MEDIUM for driving... Any questions??
Swarzkopf
Member
There is a tree in the woods. There are no animals anywhere near said tree, for miles. Certainly none close enough to hear the crash if the tree were to fall.
The tree falls. Nothing hears it. Does it make a noise?
The tree falls. Nothing hears it. Does it make a noise?
The original question stated that the treadmill rotates exactly proportional to the speed of the wheels. It doesn't matter that airplanes get their forward motion from thrust, the treadmill's still going to turn. Again, no forward motion, no fly. Now, if the wings made their own relative wind, like a real aircraft (helicopter), then we'd have flight.
The real question is, where do my socks go when I do laundry?
The real question is, where do my socks go when I do laundry?
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