Soldato
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Earth spinning
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Soldato
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I'm still 100% behind NeoDude regarding this question.
If the wheels can't turn faster than the treadmill how will the plane move forward? Please answer.
If the wheels can't turn faster than the treadmill how will the plane move forward? Please answer.
skid bounce and slide?
if they start skidding then the treadmill will stop as it's linked to their speed.
Associate
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Ok, having skipped over 6 pages of this thread - here's the situation as I see it:
You have a few different senarios here, as follows.
1. You have a plane (757) on a treadmill. The treadmill has constant velocity. With no opposing thrust from the engines, the aircraft will move backwards along with the treadmill, it's wheels not moving. It will continue like that forever.
2. You have a plane on the treadmill, but with it's engines set to produce a small amount of thrust. This thrust is enough to keep the aircraft moving along the treadmill at the same velocity as the treadmill is moving, thus cancelling eachotehr out. To the casual observer, the plane is standing still.
3. The aircraft now has enough thrust to power itself to exactly take-off speed (Vr, or Velocity Rotate) under normal circumstances. It will accelerate to this speed in relation to the conveyor belt, but it's speed relative to the air in which it is moving will be insufficient to allow it to take off. If the conveyor was moving at 30 knots, the aircraft would require a speed of Vr PLUS 30 knots to become airborne.
4. The aircraft has enough thrust to accelerate to Vr+30 knots and beyond. Upon reaching this speed, the aircraft will become airborne.
5. The aircraft has enough thrust to reach takeoff speed, but it's speed is exactly matched by the treadmill instantly. Since the aircraft's only contact with the ground is through the wheels, and these are rotating, they will simply speed up with the treadmill and to the observer the aircraft will again remain stationary. The thrust of the engines is unimportant as this is the only opposite force acting against the conveyor belt. Whatever thrust is being produced will be cancelled out by the belt instantly, and all that will change is the rotational speed of the aircraft's wheels.
The mythbusters video is irrelevant - if you had a plane pulling the conveyor belt with the same acelerative force as the plane ON the belt, the two would simply cancel eachother out.
You have a few different senarios here, as follows.
1. You have a plane (757) on a treadmill. The treadmill has constant velocity. With no opposing thrust from the engines, the aircraft will move backwards along with the treadmill, it's wheels not moving. It will continue like that forever.
2. You have a plane on the treadmill, but with it's engines set to produce a small amount of thrust. This thrust is enough to keep the aircraft moving along the treadmill at the same velocity as the treadmill is moving, thus cancelling eachotehr out. To the casual observer, the plane is standing still.
3. The aircraft now has enough thrust to power itself to exactly take-off speed (Vr, or Velocity Rotate) under normal circumstances. It will accelerate to this speed in relation to the conveyor belt, but it's speed relative to the air in which it is moving will be insufficient to allow it to take off. If the conveyor was moving at 30 knots, the aircraft would require a speed of Vr PLUS 30 knots to become airborne.
4. The aircraft has enough thrust to accelerate to Vr+30 knots and beyond. Upon reaching this speed, the aircraft will become airborne.
5. The aircraft has enough thrust to reach takeoff speed, but it's speed is exactly matched by the treadmill instantly. Since the aircraft's only contact with the ground is through the wheels, and these are rotating, they will simply speed up with the treadmill and to the observer the aircraft will again remain stationary. The thrust of the engines is unimportant as this is the only opposite force acting against the conveyor belt. Whatever thrust is being produced will be cancelled out by the belt instantly, and all that will change is the rotational speed of the aircraft's wheels.
The mythbusters video is irrelevant - if you had a plane pulling the conveyor belt with the same acelerative force as the plane ON the belt, the two would simply cancel eachother out.
Regardless, a wheel cannot move forward, whether by it's own propulsion or not if it is not moving at a relatively different speed to the surface it contacts. The question lays out that this scenario cannot happen, thereby the wheel cannot move unless it breaks traction and starts skidding and sliding along. Would a plane have enough power to take off with what effectively amounts to the wheel brakes being on? I doubt it.
As the question was posed in this thread, if you apply the laws of physics, the plane will not take off, it will end up a crumpled heap of broken plane most likely.
As the question is usually posed (and how everyone assumes it has been posed here it seems), with subtle but important differences, the plane would take off with ease.
You're thinking about it the way I was, the way the question is usually phrased. However, this question is phrased differently, in a way that is actually impossible.
Basically this version is saying that no matter what speed the wheels are at, the treadmill will always change its own speed to match that of the wheels. It's an impossible situation, but it's bascially saying that you're physically not allowing the wheels to move faster than the treadmill is, therefore the plane wouldn't move.
In the normal situation where the wheels are allowed to rotate freely, the plane would take off, anyone denying that is as mentally dense as the flat earth society.
I've totally lost track of the original question but if the wheels are in contact with a tread mill and the wheels are kept from rotating simply due to the speed of the treadmill then the plane will STILL take off.
The specific question here though is stating that the wheels are not allowed to move faster than the treadmill. We all know they are able to, but the question is worded so that the wheels are physically stopped from moving faster than the treadmill. (The likely situation that would occur is that the plane will snap somewhere due to the excess force from the engines
)Then you are as dense as the flat earth society.
The wheels can go a million miles an hour, forward, back wards or match the planes speed.
Thust is transfered from the engines into the AIR, not the wheels, plane WILL move and WILL take off no matter what the wheels are doing underneath it.
Definitely good night this time as I am round the girlfriends house now
Then you are as dense as the flat earth society.
The wheels can go a million miles an hour, forward, back wards or match the planes speed.
Thust is transfered from the engines into the AIR, not the wheels, plane WILL move and WILL take off no matter what the wheels are doing underneath it.
Definitely good night this time as I am round the girlfriends house now
Read carefully, the question is stating that the wheels are NOT ALLOWED to move faster than the treadmill, no idea why, but that's what the question is saying.
Only if it has enough thrust to take off by forcing the wheel to skid.
In very simple terms (as it was posed here) the situation is effectively the same as the plane on a normal runway with its brakes on. ie. the restraint is that the wheels cannot possibly roll forwards (regardless if they are self powered, jet powered or powered by magic moon pixies) as you would expect a wheel to do.
The question then becomes one of whether a plane has enough thrust to break the traction the wheels have with the surface and force it to skid. I'm not sure it could manage this without the tyres bursting at the very least.
The alternative of course is that the wheels and treadmill accelerate to infinite speed and stuff begins to melt from the insane friction/heat generated by such an impossible idea.
Basically, as it was posed in this thread it is highly illogical and totally impossible scenario in a variety of ways. As it is traditionally posed, the plane takes off with ease and anyone arguing against that scenario is a mental.
In very simple terms (as it was posed here) the situation is effectively the same as the plane on a normal runway with its brakes on. ie. the restraint is that the wheels cannot possibly roll forwards (regardless if they are self powered, jet powered or powered by magic moon pixies) as you would expect a wheel to do.
The question then becomes one of whether a plane has enough thrust to break the traction the wheels have with the surface and force it to skid. I'm not sure it could manage this without the tyres bursting at the very least.
The alternative of course is that the wheels and treadmill accelerate to infinite speed and stuff begins to melt from the insane friction/heat generated by such an impossible idea.
Basically, as it was posed in this thread it is highly illogical and totally impossible scenario in a variety of ways. As it is traditionally posed, the plane takes off with ease and anyone arguing against that scenario is a mental.
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And seeing as the question didnt explicitly state or even imply infinite friction between the tyres and the treadmill one can safely assume that the answer is:
It skids and then takes off.
For the plane to never be able to take off the question needs so many caveats that it's not worth asking, frictionless bearings in the treadmill, infinite friction between the tyres and treadmill surface, infinitely strong parts of everything involved.
The assumption of "speed measured as rotational speed of the wheel" is the only one you can reasonable make.
If you take one of those restrictions out of the question the plane will move, it may not take off, it might just fall over (if the struts break) but it will move off of the treadmill.
I can't believe this is still being discussed, with the same mistakes being made again.
The plane will always take off as long as normal take off thrust is applied by the engines.
The only way the plane will not take off is if the plane's wheels somehow have loads of friction and manage to anchor the plane to the treadmill. In reality they'd just spin really fast or skid.
A better question is if you put a helicopter on a fast turntable and matched the turntable speed to the rotor speed, would the helicopter take off? In this case, no. The reason being that the surface the aircraft sits on this time can prevent lift.
The plane will always take off as long as normal take off thrust is applied by the engines.
The only way the plane will not take off is if the plane's wheels somehow have loads of friction and manage to anchor the plane to the treadmill. In reality they'd just spin really fast or skid.
A better question is if you put a helicopter on a fast turntable and matched the turntable speed to the rotor speed, would the helicopter take off? In this case, no. The reason being that the surface the aircraft sits on this time can prevent lift.
While it's a more sensible question, trying to picture it is making my head feel like it's spinning
Soldato
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Can a passing mod please lock this train wreck of a thread.
Nate
Nate
So how many sandwiches are there?
I've already done that gag!
And the wheels on the plane are irrelevant, IT WILL FLY!
Soldato
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Plane won't fly if treadmill matches wheel speed exactly.
Helicopter will fly as the blades are still creating the downward thrust required for lift off.
Helicopter will fly as the blades are still creating the downward thrust required for lift off.
Soldato
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"What happens when an irresistible force meets an immovable object?"
Nate
Nate
Only if there's infinite friction keeping the tyres on the treadmill, they would just slip and it will fly.
My brain's hurting trying to picture it, but if the helicopter is centered on the turntable then the blades won't actually be moving relative to the air/ground, the body of the copter will be spinning instead.