Will the Plane Take-Off - Merged with MythBusters Show Thread
10-22-2007, 12:18 PM
#403
Go Giants
Originally Posted by cibs
nice edit
10-22-2007, 12:30 PM
#404
Senior Moderator
I wouldn't say the wheels have no bearing. I mean if the wheels were seized or replaced with metal blocks, it would surely impede the forward movement of the plane. But the opposing force in the case of water, or ice, or with wheels (assuming there is nothing stopping how fast they can turn) is minimal.
10-22-2007, 12:33 PM
#405
Three Wheelin'
Just because both planes and cars have wheels and tires does not mean they rely on the same force for forward movement relative to space.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
10-22-2007, 12:40 PM
#406
Senior Moderator
Originally Posted by levon1830
Just because both planes and cars have wheels and tires does not mean they rely on the same force for forward movement relative to space.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
Agreed, assuming the wheels can turn fast enough so that there is no opposing force. If the wheels couldn't turn fast enough, were seized or were replaced with metal blocks, then there would be an opposing force at play here. That said, if the plane had enough power it would still take off anyways.
10-22-2007, 12:56 PM
#409
Three Wheelin'
Originally Posted by fdl
Agreed, assuming the wheels can turn fast enough so that there is no opposing force. If the wheels couldn't turn fast enough, were seized or were replaced with metal blocks, then there would be an opposing force at play here. That said, if the plane had enough power it would still take off anyways.
1. The plane would have ample power.
2. The wheels bearings were lubricated using Astroglide.
10-22-2007, 01:28 PM
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10-22-2007, 01:36 PM
#413
I shoot people
Originally Posted by bent09
10-22-2007, 01:39 PM
#414
Go Giants
Originally Posted by is300eater
so, there's going to be a big giant fan like that? I didn't know that was part of the experiment...
The fan will give lift under then wings, as long as the flaps are down, plane should go up...
10-22-2007, 01:55 PM
#416
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It will not take off!! the plane is generating thrust, but remains stationary therefore there is no wind moving under or over the wing, which means no lift.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
10-22-2007, 01:57 PM
#417
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Originally Posted by AQUI NO!
It will not take off!! the plane is generating thrust, but remains stationary therefore there is no wind moving under or over the wing, which means no lift.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh
10-22-2007, 02:00 PM
#419
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Originally Posted by cibs
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh
NO WIND = NO LIFT = NO TAKEOFF
10-22-2007, 02:02 PM
#420
Three Wheelin'
Originally Posted by AQUI NO!
It will not take off!! the plane is generating thrust, but remains stationary therefore there is no wind moving under or over the wing, which means no lift.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
If any one has access to a thread mill and remote control car. Place a flag on the car's roof, place said car on the thread mill and rev up car, if the car is traveling at the same rate as the treadmill, there should be no movement from the flag.
Originally Posted by levon1830
Just because both planes and cars have wheels and tires does not mean they rely on the same force for forward movement relative to space.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
The critical difference is a plane relies upon thrust (reaction force on air molecules) for forward movement, not friction with the ground (like a car). A plane sitting on a treadmill that is spinning in the opposite direction of the plane's intended forward movement will not negate the plane engines' reaction force on the air molecules around them.
Regardless of the conveyor belt, the plane will achieve forward movement relative to space, thereby achieving lift. The plane will take off.
10-22-2007, 02:03 PM
#421
Go Giants
Originally Posted by cibs
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh
Something like this would take off, because the jets are pushing air down, not behind it...
10-22-2007, 02:04 PM
#422
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[QUOTE=cibs]
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh,
I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed.
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh,
I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed.
10-22-2007, 02:05 PM
#423
Go Giants
Originally Posted by revitupwriteitoff
it doesn't matter what it uses for propulsion, the point is that if it doesn't have wind hitting the wings, there is no lift. even if there was no treadmill & the plane was just on a runway inside a vacuum, it could travel thousands of miles/hr in a straight line but would never take off w/o wind to create the lift against the wings.
NO WIND = NO LIFT = NO TAKEOFF
NO WIND = NO LIFT = NO TAKEOFF
10-22-2007, 02:05 PM
#424
Insert Sarcasm Here
OK Different look at the problem...
It's not that the plane would take off from a relative standstill on the belt; it's that—because the plane doesn't rely on wheel friction for its horizontal motion—the belt wouldn't hold it back: instead, the thrust of the engines would be enough to roll the plane right off the belt and forward from there (presumably on a runway of some sort, which would still be needed), so it could take off
It's not that the plane would take off from a relative standstill on the belt; it's that—because the plane doesn't rely on wheel friction for its horizontal motion—the belt wouldn't hold it back: instead, the thrust of the engines would be enough to roll the plane right off the belt and forward from there (presumably on a runway of some sort, which would still be needed), so it could take off
10-22-2007, 02:06 PM
#425
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Originally Posted by revitupwriteitoff
it doesn't matter what it uses for propulsion, the point is that if it doesn't have wind hitting the wings, there is no lift. even if there was no treadmill & the plane was just on a runway inside a vacuum, it could travel thousands of miles/hr in a straight line but would never take off w/o wind to create the lift against the wings.
NO WIND = NO LIFT = NO TAKEOFF
NO WIND = NO LIFT = NO TAKEOFF
the skateboard example I posted up a page ago illustrates it perfectly.
Why do you say that the plane won't move forward? All that will happen is the wheels would spin twice as fast as normal...
10-22-2007, 02:07 PM
#426
Go Giants
Originally Posted by Smalls
OK Different look at the problem...
It's not that the plane would take off from a relative standstill on the belt; it's that—because the plane doesn't rely on wheel friction for its horizontal motion—the belt wouldn't hold it back: instead, the thrust of the engines would be enough to roll the plane right off the belt and forward from there (presumably on a runway of some sort, which would still be needed), so it could take off
It's not that the plane would take off from a relative standstill on the belt; it's that—because the plane doesn't rely on wheel friction for its horizontal motion—the belt wouldn't hold it back: instead, the thrust of the engines would be enough to roll the plane right off the belt and forward from there (presumably on a runway of some sort, which would still be needed), so it could take off
10-22-2007, 02:07 PM
#427
Three Wheelin'
[QUOTE=AQUI NO!]
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh, I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed.
The plane will move forward relative to space.
Originally Posted by cibs
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh,
I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed.
10-22-2007, 02:08 PM
#428
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[QUOTE=AQUI NO!]
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh, I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed.
you can't, because an RC car moves forward using it's wheels. It's wheels push it forward right? If the conveyor belt moves back at the same speed then the car will appear to be stationary.
The RC car uses a different source of propulsion than an airplane.
i.e. you put your car on a dyno, the wheels are spinning like mad, but the car isn't going anywhere.
put a jet's wheels on a dyno and see what happens... i'm sure it'll just sit there and not move
Originally Posted by cibs
a plane doesn't move forward using it's wheels it uses thrust from engines either jet or propeller driven...
*sigh[/QUOTE
Sigh,
I never said the wheels were the source of thrust, i'm simply stating that if the plane is stationary in space(doesn't matter what the source of thrust is), there is no wind moving under or over the wings, therefor there is no lift. To check if air flow is generated, you can try the RC car experiment, the flag should remain fixed. you can't, because an RC car moves forward using it's wheels. It's wheels push it forward right? If the conveyor belt moves back at the same speed then the car will appear to be stationary. The RC car uses a different source of propulsion than an airplane.
i.e. you put your car on a dyno, the wheels are spinning like mad, but the car isn't going anywhere.
put a jet's wheels on a dyno and see what happens... i'm sure it'll just sit there and not move
10-22-2007, 02:09 PM
#429
Go Giants
Originally Posted by cibs
It will have 'wind' hitting the wings because it will move forward...
the skateboard example I posted up a page ago illustrates it perfectly.
Why do you say that the plane won't move forward? All that will happen is the wheels would spin twice as fast as normal...
the skateboard example I posted up a page ago illustrates it perfectly.
Why do you say that the plane won't move forward? All that will happen is the wheels would spin twice as fast as normal...
10-22-2007, 02:11 PM
#431
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Put an RC car on a treadmill and place it in neutral. Hold it down and turn on the treadmill and it just sits there, yes the same as if it's in gear and you are matching the speed with the throttle. Now turn the treadmill up to any speed you like and it still sits there, but the wheels are spinning faster, now push the car forward with your hand= thrust... and the car moves forward and which air now flows over the car in a forward motion= the plane will move forward no matter how fast the wheels are spinning. Tie a rope to the front of the plane while all this is going on and pull it, does it move forward... yes, same as someone pushing the plane from the rear. A prop or jet engine will move a plane no matter what it's sitting on!
Last edited by Bdog; 10-22-2007 at 02:15 PM.
10-22-2007, 02:11 PM
#432
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Originally Posted by Whiskers
If you run on a treadmill, do you feel wind against your face? No...
maybe he does...<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/db1b35UJ_4I"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/db1b35UJ_4I" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>
10-22-2007, 02:12 PM
#433
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Originally Posted by Whiskers
If you run on a treadmill, do you feel wind against your face? No...
Planes however do not put force DOWN through their wheels they push force out through their engines.
A planes wheels are only there so that it minimizes friction between the plane and the ground. Not to make it move forwards.
You cannot compare a plane to a car in a situation like this. You'd have to compare something that has a 'thrust force' found somewhere OTHER than the ground.
i.e. a helicopter on a platform that is falling as fast as it's blades are creating lift
Just like when you exercise on a stepping machine, you are exerting force to step up at the same time as the step is coming down, you go nowhere yet you just climbed 1000 stairs.
Put a jetpack on you back and all of a sudden that's no longer an issue.
Last edited by cibs; 10-22-2007 at 02:15 PM.
10-22-2007, 02:13 PM
#434
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Been reading this for awhile. Have to agree with Levon. It definitely could take flight. Actually, I've been waiting for Stright-(Paint)Balling to chime in to help illustrate the scinerio. 
10-22-2007, 02:14 PM
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Originally Posted by Bdog
Put an RC car on a treadmill and place it in neutral. Hold it down and turn on the treadmill and it just sits there, yes the same as if it's in gear and you are matching the speed with the throttle. Now turn the treadmill up to any speed you like and it still sits there, but the wheels are spinning faster, now push the car forward with your hand= thrust... and the car moves forward and which air now flows over the car in a forward motion= the plane will move forward no matter how fast the wheels are spinning.
10-22-2007, 02:14 PM
#436
Three Wheelin'
Originally Posted by Bdog
Put an RC car on a treadmill and place it in neutral. Hold it down and turn on the treadmill and it just sits there, yes the same as if it's in gear and you are matching the speed with the throttle. Now turn the treadmill up to any speed you like and it still sits there, but the wheels are spinning faster, now push the car forward with your hand= thrust... and the car moves forward and which air now flows over the car in a forward motion= the plane will move forward no matter how fast the wheels are spinning.
10-22-2007, 02:15 PM
#437
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Originally Posted by levon1830
The plane will move forward relative to space.
10-22-2007, 02:18 PM
#438
Go Giants
Originally Posted by levon1830
That's because you're not moving forward relative to space.
10-22-2007, 02:18 PM
#439
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Originally Posted by AQUI NO!
How? isn't the thread mill supposed to match the thrust of the plane so it remains still? If the plane is moving forward relative to space, it will eventually reach fixed ground and shoot off at whatever rate of speed it was moving on the threadmill, only then will it achieve flight
you are assuming that the speed of the wheels turning = the real speed of the plane in space.
that simply isn't true.
does the thrust of the plane have anything to do with the treadmill that's moving underneath it? NO.
The planes engines are pushing huge masses of air behind it to move the airplane forwards relative to the atmosphere on earth.
The conveyor belt is simply making the wheels turn more than they would ordinarily.