Can Plane Take Off

Twobit_sl

shitlord
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You think the air a propellor pushes is what generates the lift that allows a plane to take off?

A prop plane.. with vertical launch capability?

Wow...
 

TOOL_foh

shitlord
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Torrid said:
Although this brings up a point I neglected to mention in my post, which was that the prop plane was a V-22 Osprey pointed at an upward angle. I"m just saying that I don"t think that alone is the reason why it took off, and that many aircraft (especially the space shuttle) would be unable to take off that way.
Dude, what?
 

Aulirophile_foh

shitlord
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Torrid said:
Well, if the rocket thrust was aimed exactly parallel to the conveyor belt, yes.

Keeping in mind that this is a hypothetical scenario, and not considering things like the amount of friction holding down the plane on the conveyor.

Although this brings up a point I neglected to mention in my post, which was that the prop plane was pointed at an upward angle. I"m just saying that I don"t think that alone is the reason why it took off, and that many aircraft (especially jets) would be unable to take off that way.



The conveyor doesn"t do nothing. It decreases the speed of the air relative to the plane.



No, I said the opposite. I said that IF conveyors always worked, then they would be used on aircraft carriers. If they worked, they would essentially give every plane vertical take off capability.

I"m just tossing ideas out here is all. I suppose I should have known better to reply to a 3 year old thread though.
I"m going to repeat this one more time, slowly, because I honestly know exactly where you"re being an idiot.

The plane is on a conveyer belt. The belt speeds up when the plane does, in the opposite direction. The question never insists that the converyer keeps the plane stationary. That is the "trick" to the question. Since a planes forward momentum is generated by a prop/rocket/jet and NOT at the wheels, the conveyer CANNOT prevent the plane from moving forward. Plane moves forward, generates lift. The downside is the runway needs to be twice as long to generate air speed (notice how all speeds in a plane are called "air speed", even when on the ground) and the wheels needs to spin twice as fast. It doesn"t magically cause them to VTOL.

I doubt you"ll get it, since you think the conveyer can magically change the speed of air in it"s general vicinity, but hey, I tried.
 

Twobit_sl

shitlord
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Let me chime in with my crappy example, a variation of the test they did in the Mythbusters episode.

Kids, try this at home. Take a Hot Wheels or Matchbox (if you are poor) car and hold it by the sides in one hand. Now run your other hand across the wheels. The wheels spin but the car doesn"t move does it? Now run your hand across it faster. Still doesn"t move does it? Now move the hand holding the car forward while running your hand across the wheels... then do it faster. The car will move forward regardless of how fast you move your hand across the wheels.

Replace your hand holding the car with the plane"s propeller or engine and replace your other hand with the conveyor belt and there you go. The wheels on the plane will always be spinning at the speed of the conveyor belt + the thrust generated by the plane"s engine. This continues until there is a mechanical failure, the plane takes off or you reach infinity and beyond.
 

Torrid_foh

shitlord
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Okay, first of all I"ll admit I"m a fucking retard. I had a bad feeling when I hit post the first time. (hence the unsuredness tone of my posts) I was pondering the question some more and I figured out my error. Serves me right for putting 5 minutes of thought to such a hotly debated issue. Cut me some slack though, even some pilots don"t get it Faded memories of the show I half paid attention to didn"t help either.

I do want to clarify some things to slightly mitigate the humiliation though.

Aulirophile said:
I"m going to repeat this one more time, slowly, because I honestly know exactly where you"re being an idiot.

The plane is on a conveyer belt. The belt speeds up when the plane does, in the opposite direction. The question never insists that the converyer keeps the plane stationary. That is the "trick" to the question.
Yeah, I was just thinking that the conveyor was intended to represent a force pushing back on the plane to nullify forward momentum, so I didn"t put any thought into friction considerations at all. Of course that is no excuse for letting that train of thought continue into real life scenarios. Boy is that no excuse. I hate myself.

Aulirophile said:
I doubt you"ll get it, since you think the conveyer can magically change the speed of air in it"s general vicinity, but hey, I tried.
I said speed of the air RELATIVE to the plane. Relative being the keyword in that sentence.

Twobit Whore said:
You think the air a propellor pushes is what generates the lift that allows a plane to take off?
I said (more of a guess really) that the prop pushing air over the wings creating lift was A (as in, one of several) reasons why the plane lifted off, albeit the most significant. I don"t think that reasoning is too nutty (even if incorrect) considering the amount of air speed needed to take off in the plane used on the show was unusually low (25 mph), because it was an ultralight. Although now that I think about it more, I don"t think that air speed/propwash/whatever would really cover the entire wing surface area that well. So yeah, I"m retarded.

Anyway, I apologize for wasting everybody"s time, and hope you got some amusement from my humiliation.
 

Camerous

Bronze Knight of the Realm
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Torrid said:
I said (more of a guess really) that the prop pushing air over the wings creating lift was A (as in, one of several) reasons why the plane lifted off, albeit the most significant.
The prop has zero to do with the air going over the wings... ALL the prop does is pull the plane forward, almost the same as a jet engine but the jet engine PUSHES the plane forward. This forward movement is what creates the air over the wings or the lift needed to take off. Since the wheels on a plane are free moving, which means they are not attached to any mechanical means of moving them they just spin, the conveyor doesn"t do anything but force the plane to increase it"s acceleration to compensate for the conveyor belt. That"s the whole answer. Done. Written so you can read it in easy to understand terms.
 

Twobit_sl

shitlord
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Camerous said:
Since the wheels on a plane are free moving, which means they are not attached to any mechanical means of moving them they just spin, the conveyor doesn"t do anything but force the plane to increase it"s acceleration to compensate for the conveyor belt. That"s the whole answer. Done. Written so you can read it in easy to understand terms.
That"s not entirely correct. In a hypothetical frictionless world it would take very minimal force to keep the plane moving forward no matter how fast the conveyor belt was spinning. The wheels would just spin faster. The only reason why it could possibly increase the force required is by the friction in the bearings being transmitted from the axle to the plane.
 

Cad

scientia potentia est
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Torrid said:
I said (more of a guess really) that the prop pushing air over the wings creating lift was A (as in, one of several) reasons why the plane lifted off, albeit the most significant. I don"t think that reasoning is too nutty (even if incorrect) considering the amount of air speed needed to take off in the plane used on the show was unusually low (25 mph), because it was an ultralight. Although now that I think about it more, I don"t think that air speed/propwash/whatever would really cover the entire wing surface area that well. So yeah, I"m retarded.
While I agree you are retarded, even if the prop were 20 feet wide and covered the entire plane it wouldn"t take off by air pushed from it over the wings. I can"t even categorize all the reasons why it wouldn"t work, from laminar flow to the ridiculous amount of air you"d have to move to make it work. What you"re describing is a helicopter, and those don"t work by a prop blowing air over a wing.
 

Sylas

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Plane moves forward, generates lift. The downside is the runway needs to be twice as long to generate air speed (notice how all speeds in a plane are called "air speed", even when on the ground) and the wheels needs to spin twice as fast. It doesn"t magically cause them to VTOL.
How the hell does the runway need to be twice as fucking long? The moment the plane (via propeller or jet engine) generates enough thrust to overcome the friction from the wheels/bearings, the plane begins to move forward. Until that point the plane is moving backwards (assuming the conveyor belt speed is matching the forward thrust) or otherwise is not moving at all (waiting on the plane to generate some forward ground movement to kick on and start moving in the opposite direction).

Once the plane generates enough thrust to move forward, it continues to move forward as if it was on a regular runway, the conveyor does ABSOLUTELY FUCK ALL except make the wheels spin faster.
 

Zuuljin_foh

shitlord
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Kazgrim said:
How the hell does the runway need to be twice as fucking long?
Haha not quite sure where he was going with that, but he"s kind of correct. If it takes a plane say 200ft to take off on a stationary runway, then it will require 400ft of runway if the runway is now moving toward the plane as the plane speeds up.

Completely pointless yes, but not entirely wrong.
 

Sylas

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No, the conveyor belt has to be 400+ feet long. The runway still only needs to be 200.
 

Frawdo_foh

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Regarding the ice cube in the glass question, I"ve done some thinking and have just completed some preliminary analysis and liquid solid phase diagrams, and I"ve concluded that the water level both remains unchanged and changes.

A few folks imply that density differentials relative to the ice and water are the the reason for water level changing. As per the universal laws of chemistryandphysics, this is not the case.

Folks who know a bit about water phase changes here say that there is no change in water level because a floating object displaces an amount of water equal to its own weight. Since water expands when it freezes, one ounce of frozen water has a larger volume than one ounce of liquid water.

Nonetheless, the ice cube melts in real discrete time, and by the universal laws of gravitationandNewton"s First Law, the freshly melted water moves downwards and briefly occupies more volume than the ice previously did. Since the water level takes time to react, and the freshly melted water is ever present and increasing, then the water level is lurching back and forth at small increments, while the water level adjusts (decreases) to meet the increase from the melted water.

Thus, the water level both changes and does not change, going by the consensus of those who know more about water phase changes, the laws of physics, and those who have had more time with the problem, but ignoring peoples" specific answers as to whether the water level changes.

Therefore, we have a paradox that can only be resolved through math or experimentation, even if all components are ideal with the exception that the ice and liquid water both have different densities (they would have to for this to make any sense).

Could it be that something in the original question was misquoted?
 

squong_foh

shitlord
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Frawdo said:
Regarding the ice cube in the glass question, I"ve done some thinking and have just completed some preliminary analysis and liquid solid phase diagrams, and I"ve concluded that the water level both remains unchanged and changes.

A few folks imply that density differentials relative to the ice and water are the the reason for water level changing. As per the universal laws of chemistryandphysics, this is not the case.

Folks who know a bit about water phase changes here say that there is no change in water level because a floating object displaces an amount of water equal to its own weight. Since water expands when it freezes, one ounce of frozen water has a larger volume than one ounce of liquid water.

Nonetheless, the ice cube melts in real discrete time, and by the universal laws of gravitationandNewton"s First Law, the freshly melted water moves downwards and briefly occupies more volume than the ice previously did. Since the water level takes time to react, and the freshly melted water is ever present and increasing, then the water level is lurching back and forth at small increments, while the water level adjusts (decreases) to meet the increase from the melted water.

Thus, the water level both changes and does not change, going by the consensus of those who know more about water phase changes, the laws of physics, and those who have had more time with the problem, but ignoring peoples" specific answers as to whether the water level changes.

Therefore, we have a paradox that can only be resolved through math or experimentation, even if all components are ideal with the exception that the ice and liquid water both have different densities (they would have to for this to make any sense).

Could it be that something in the original question was misquoted?
gg, and made sense, props for that