Can Plane Take Off

Hooby said:

That arguement would be valid if you were talking about speed and not velocity. You can go around the world in 80 days but if you end up at the exact same spot your velocity will be 0. Velocity is speed over a distance, IE: If you are going at a constant speed of 100mph, head directly north for 30 minutes; then turn directly east for 30 minutes, your average velocity will be 71 mph NE not 100mph. (50^2 + 50^2 = c^2).

If you head out to pick up dinner and drive back to where you came from no matter how far you went your average velocity for the entire trip is 0, which should explain the 0m/s thing.

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You seriously think I don"t fucking know that? Go back and re-read my post and when you come to the word "velocity" insert "speed". Happy now? What you just said has no bearing my the idea. It does not "explain the 0m/s thing".

And for the record, velocity is not "speed over a distance", velocity is speed with direction. I know what you meant, but velocity over a distance would be more like, I don"t know, inverse time or some shit.

The belt would just make the wheels spin faster, it wouldn"t actually slow down the plane, and it would still move forward. Thus, lift is generated and it takes off. If we were talking about a car with wings where the forward force was generated at the wheels, then no it would not take off. However, a jet will. If you think otherwise, you"re wrong.

Someone should make a "is .999 repeating = 1" thread, just to continue the clusterfuck.

I"ll try again.

The plane pulls itself through the air and space, it does not push against the ground. Therefore, without moving forward through space, it cannot move at all. Therefore, since the conveyor is set to the speed of the plane, and the plane must be moving through space to be moving at all, according to its nature, if the plane does not move through space the conveyor does not move at all. So then, if you understand that concept you know that the wheels are merely holding it off the ground while the plane moves forward, and the conveyor"s speed is fairly irrelelvant unless your plane is not capable of generating enough thrust to overcome the friction being caused by the conveyor. I don"t know if such a plane could get airborne under any circumstances.

Exactly.

Frawdo said:

You seriously think I don"t fucking know that? Go back and re-read my post and when you come to the word "velocity" insert "speed". Happy now? What you just said has no bearing my the idea. It does not "explain the 0m/s thing".

And for the record, velocity is not "speed over a distance", velocity is speed with direction. I know what you meant, but velocity over a distance would be more like, I don"t know, inverse time or some shit.

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What I said did have a bearing if you said the correct word. I even stated that if you replaced it with speed it would be correct, but stated as velocity it didn"t. I see people who don"t know the differences between speed and velocity all the time so I just assumed you chose the correct word but applied the wrong meaning, rather than the other way around. Was a 50/50 guess .

And that"s my bad with the distance thing, not used to having to explain it in a way that would make sense to anyone who doesn"t share my eccentric pun-obsessed physics teacher.

Edit: Foghorn --> W

Hooby said:

What I said did have a bearing if you said the correct word. I even stated that if you replaced it with speed it would be correct, but stated as velocity it didn"t. I see people who don"t know the differences between speed and velocity all the time so I just assumed you chose the correct word but applied the wrong meaning, rather than the other way around. Was a 50/50 guess .

And that"s my bad with the distance thing, not used to having to explain it in a way that would make sense to anyone who doesn"t share my eccentric pun-obsessed physics teacher.

Edit: Foghorn --> W

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so when do you turn 15 and realize that because you took a highschool class about physics give you no right to critiscize people on the internet? it only gives me the right

And you just pulled your winky out of your best friend"s ass...

That arguement would be valid if you were talking about speed and not velocity. You can go around the world in 80 days but if you end up at the exact same spot your velocity will be 0. Velocity is speed over a distance, IE: If you are going at a constant speed of 100mph, head directly north for 30 minutes; then turn directly east for 30 minutes, your average velocity will be 71 mph NE not 100mph. (50^2 + 50^2 = c^2).

If you head out to pick up dinner and drive back to where you came from no matter how far you went your average velocity for the entire trip is 0, which should explain the 0m/s thing.

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Velocity is completely dependent on your point of reference though. If your point of reference is a spot on the earth, then yeah fine in your above examples you"d have a zero velocity. However if it"s based on a fixed point in space, like say the sun (which itself isn"t actually fixed either), then you"d have a pretty ridiculously high velocity the entire time, unless you"ve got one awesome car than can travel back to the point in earth"s orbit you were at when you left for dinner.

Just wanted to clarify that.

Did he say anywhere that the plane was in an atmosphere? If it"s in a vacuum, you"d get no lift except possibly from the equal/opposite force from any exhaust gases from the engine if they pointed down at all. Use an electrical engine (or a rubber band if it"s a really tiny plane!) = no exhaust = move the conveyor at any speed and the plane isn"t going up at all...

RdT.

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Except that you know, plane engines don"t work in a vacuum, cause they need "oxygen." I know, wild eh?

As far as an electric engine, what the fuck are you even talking about? An electric engine to spin the wheels of a plane until it took off, and uh, then what?

<3 Eomer

This thread has caused me to respect many of y"all on new level.

how is this tricky at all? it"s exactly the same as a car on a dyno. the plane won"t do shit; no fancy physics needed. air isn"t moving over the wings so there is no lift. the wheels will spin and that"s it. this would not be a fun environment to hang around in as the gusts generated by the plane might get pretty powerful...

bcware said:

how is this tricky at all? it"s exactly the same as a car on a dyno. the plane won"t do shit; no fancy physics needed. air isn"t moving over the wings so there is no lift. the wheels will spin and that"s it. this would not be a fun environment to hang around in as the gusts generated by the plane might get pretty powerful...

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And yet the plane takes off.....

Zuuljin said:

And yet the plane takes off.....

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you win

a car on a dyno doesnt move because a car is propelled forward by the friction created through the wheels.

an airplane is propelled forward by the propeller acting as a wind screw. so unless the treadmill is pushing air at the airplane it wont affect its velocity.

been rehashed a million times

findar said:

a car on a dyno doesnt move because a car is propelled forward by the friction created through the wheels.

an airplane is propelled forward by the propeller acting as a wind screw. so unless the treadmill is pushing air at the airplane it wont affect its velocity.

been rehashed a million times

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is there a difference between "pulling" air and "pushing" via jet propulsion? i would imagine at low speeds propeller powered planes, which tend to sit on a tripod set of wheels with the nose pointed upward, would do nothing but spin the wheels. As the plane picks up speed and just before it takes off, the plane straightens out and the 3rd wheel in the rear comes off the ground. I would think that a propeller based plane with this tilted tripod setup would do nothing more but lift it?s 3rd wheel in the rear off the ground once the propeller spins fast enough to level the plane. A jet, however, ?pushes? and doesn?t pull, they also sit relatively flat don?t they? Do the physics change completely? The wheels on the plane don?t generate any force; they just provide a means to transfer the power to the ground until speed is sufficient to generate lift. I just feel like the wheels must ?push? off something to get the plane going. Intuitively the physics of a plane and car don?t seem all that different until the plane actually leaves the ground.

I wanna see the physics guys? I haven?t taken enough physics to say anything useful here.

edit:

a plane uses the same friction to move until it reaches sufficient speed to generate lift. Exactly the same way a car does, it just generates it?s power to move via a different source. There is no drive train connected to a plane?s wheels because it isn?t necessary, we can ?drive? forward by pulling air instead of pavement, but the same driving force is transferred to the wheels which push off the ground and move the plane forward. The fundamentally seems exactly the same as a car to me. the only difference is that when the plane moves fast enough a second set of physics kicks in and lift is generated. i think the dyno-plane thing is possible and wouldnt fly, but obviously it"d be an extremely dangerous equilibrium to maintain. pull the wings off a plane and what does it do? it"s a propellar powered car isn"t it? i think the key to fully understanding this problem is breaking this problem into different distinct pieces.

There is no drive train connected to a plane?s wheels because it isn?t necessary, we can ?drive? forward by pulling air instead of pavement, but the same driving force is transferred to the wheels which push off the ground and move the plane forward. The fundamentally seems exactly the same as a car to me. the only difference is that when the plane moves fast enough a second set of physics kicks in and lift is generated.

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You know, normally I try not to flame people unless they really deserve it. But holy shit man, this really demonstrates a fundamental deficiency in cognitive ability on your part.

An airplanes wheels are not pushing on anything. Again, think of a single roller blade, or a toy car, or a tricycle, or whatever. Give it a push, and it moves. What is causing it to move? Your push? Or your push somehow magically transferring to the wheel axels causing them to move through some unseen force, rotating the wheels, and the ground giving an equal and opposite push back on the wheels? Think about it. Christ.

The answer is no.

Done.

To all you "physicists" (yes, they"re sneer quotes...), I have a few questions:

1) What makes a plane fly? (My answer is that it has something to do the way AIR moves across the wings, but I could be wrong)

2) Is air flowing across the wings of the plane? (If yes, explain how)

As I see it there is no air moving across the wings, so there is no lift. My conclusion is that the plane doesn"t fly. If I"m wrong, show me how by answering my two questions.

how is air not moving across the wings?

if the jet engines are firing, the plane is moving forward unless the brakes are applied. period.