YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 it doesnt MATTER what kind of plane no airflow = no lift no lift = no fly the prop pulls the plane causing momentom not airflow momentom creates the air flow causing the lift. it will fly if the engine is pushing/pulling it. The speed of the aircraft is measured thru the pitot tube which is airspeed not ground speed. If the plane is going 300 knots, it does not matter what the wheels are doing (they could be spnning 1000mph). If the wheels were driving the plane like a car then it would sit still and not move forward but the jet or prop is moving the plane to speed thus creating lift. an example on the opposite side would be if the wheels don't turn can the plane take off..of course.you could be on ice and the wheels locked but the plane still moves forward creating lift. also, look at a harrier(sp) its wheels could be spinning on a convayor and it would still take off. Quote Link to comment Share on other sites More sharing options...
powerhouse Posted November 8, 2007 Share Posted November 8, 2007 it will fly if the engine is pushing/pulling it. The speed of the aircraft is measured thru the pitot tube which is airspeed not ground speed. If the plane is going 300 knots, it does not matter what the wheels are doing (they could be spnning 1000mph). If the wheels were driving the plane like a car then it would sit still and not move forward but the jet or prop is moving the plane to speed thus creating lift. an example on the opposite side would be if the wheels don't turn can the plane take off..of course.you could be on ice and the wheels locked but the plane still moves forward creating lift. also, look at a harrier(sp) its wheels could be spinning on a convayor and it would still take off. absolutly not Quote Link to comment Share on other sites More sharing options...
dunefreak Posted November 8, 2007 Share Posted November 8, 2007 I think Yamakiller thinks that this imaginary "conveyor belt" is going forward, not backwards. I can't beleive we are talking about some stupid chit like this. Quote Link to comment Share on other sites More sharing options...
YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 absolutly not ex aircraft engineer...absolutly.. get to work anyway...you need to be builing something to beat me Quote Link to comment Share on other sites More sharing options...
SandBox_Kid Posted November 8, 2007 Share Posted November 8, 2007 ex aircraft engineer...absolutly.. get to work anyway...you need to be builing something to beat me According to the description I could stand off to the side of the runway and the plane isn't moving. How do you get lift when the plane is actually sitting still? Quote Link to comment Share on other sites More sharing options...
powerhouse Posted November 8, 2007 Share Posted November 8, 2007 ex aircraft engineer...absolutly.. get to work anyway...you need to be builing something to beat me ok ! god [ and it won't fly, I don't care who you talked to .] Quote Link to comment Share on other sites More sharing options...
YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 I think Yamakiller thinks that this imaginary "conveyor belt" is going forward, not backwards. I can't beleive we are talking about some stupid chit like this. forward or backwards don't matter. if the speed of the aircraft is 300mph that is measured by the aircraft moving thru the air at 300 mph not measured by wheel speed even if the wheels are touching the ground(conveyor belt). If the aircraft is moving thru the air at 300 mph = LIFT like we have anything better to do while waiting to get back out there Quote Link to comment Share on other sites More sharing options...
desertskyz Posted November 8, 2007 Share Posted November 8, 2007 (edited) According to the description I could stand off to the side of the runway and the plane isn't moving. How do you get lift when the plane is actually sitting still? Downward thrust. Like a Herrier Jet. Edited November 8, 2007 by desertskyz Quote Link to comment Share on other sites More sharing options...
YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 According to the description I could stand off to the side of the runway and the plane isn't moving. How do you get lift when the plane is actually sitting still? that is the one point I am trying to make. If the conveyor belt is measuring aircraft speed and it sees the plane is going 300 mph and it spins backwards 300 mph, the aircraft must be moving forward to get that measuement. It must be moving thru the air at 300 mph to have it measured thru the pitot tube. It does not measure wheel speed so it must be flying Quote Link to comment Share on other sites More sharing options...
sandstarved Posted November 8, 2007 Share Posted November 8, 2007 I like burritos! Quote Link to comment Share on other sites More sharing options...
powerhouse Posted November 8, 2007 Share Posted November 8, 2007 forward or backwards don't matter. if the speed of the aircraft is 300mph that is measured by the aircraft moving thru the air at 300 mph not measured by wheel speed even if the wheels are touching the ground(conveyor belt). If the aircraft is moving thru the air at 300 mph = LIFT like we have anything better to do while waiting to get back out there IF THE PLANE IS NOT MOVING, TO GET THE AIR FLOWING UNDER THE WINGS ,IT WILL NOT FLY !! PERIOD if you put you bike on a treadmill at the bottom of the hill would you beat anything up the hill ? NO !! why? because the turd is not moving !!!!!!!! Quote Link to comment Share on other sites More sharing options...
SandBox_Kid Posted November 8, 2007 Share Posted November 8, 2007 No wonder we have to fight for our dunes......we can't even agree on a stupid riddle. It's also amazing to see how deeply everyone is reading into this. Jets.....harriers......air speed and how it's measured. KISS Quote Link to comment Share on other sites More sharing options...
desertskyz Posted November 8, 2007 Share Posted November 8, 2007 I like burritos! You spelt alcohol wrong in your signature. Quote Link to comment Share on other sites More sharing options...
wingnut Posted November 8, 2007 Share Posted November 8, 2007 I like turtles.......... A helicopter could take off Quote Link to comment Share on other sites More sharing options...
YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 IF THE PLANE IS NOT MOVING, TO GET THE AIR FLOWING UNDER THE WINGS ,IT WILL NOT FLY !! PERIOD if you put you bike on a treadmill at the bottom of the hill would you beat anything up the hill ? NO !! why? because the turd is not moving !!!!!!!! if my bike was on a treadmill at the bottom of the hill and you strapped a J.A.T.O. (jet engine)bottle on me would I move then...Yes...does not matter what my wheels are doing the turd would fly Quote Link to comment Share on other sites More sharing options...
EY3BA11 Posted November 8, 2007 Share Posted November 8, 2007 so if you strapped wings on a hampster and hung a piece of cheese above the wheel and he ran really really really really fast inside the wheel... would he take off... ummm NO!!! Quote Link to comment Share on other sites More sharing options...
powerhouse Posted November 8, 2007 Share Posted November 8, 2007 (edited) wow , I missed the whole thing !!! sorry ! I'm working , stop hassling me !! and it still won't fly ... Edited November 8, 2007 by powerhouse Quote Link to comment Share on other sites More sharing options...
EY3BA11 Posted November 8, 2007 Share Posted November 8, 2007 im not a engineer just a dumb pilot Quote Link to comment Share on other sites More sharing options...
ltr450rider Posted November 8, 2007 Share Posted November 8, 2007 Yamakiller: The plane WILL NOT take off. The only way it would take off is if there was a huge fan in front of the plane pushing air beneath the wings to give it lift. If your on a treadmill at the gym, Do you actually go anywhere. No. Your running in the same spot all the time. This is the same idea. The plane is not actually moving through air, It's staying in the same exact position on the earth. You can't fight it, it's a law of physics. Harrier jets take off because they have downward thrust like a helicopter. Not because there is airflow under the wings. And if you are fighting this to , damn good job. You have succeeded. Quote Link to comment Share on other sites More sharing options...
dunefreak Posted November 8, 2007 Share Posted November 8, 2007 I already tried it. It doesn't work. Quote Link to comment Share on other sites More sharing options...
ltr450rider Posted November 8, 2007 Share Posted November 8, 2007 Damn that was a quick cut and paste. Quote Link to comment Share on other sites More sharing options...
Vegas FX400 Posted November 8, 2007 Share Posted November 8, 2007 Quote Link to comment Share on other sites More sharing options...
sanddunesaddict Posted November 8, 2007 Share Posted November 8, 2007 Ok peeps here it is... IF the planes engines are off it will only go backwards, roll the tires and not take off. IF the engines are on the tires will turn and the plane will stay in place untill the engines propel it to take off AIR speed. It doesnt say whether they are on or off!!! Quote Link to comment Share on other sites More sharing options...
YamaKiller Posted November 8, 2007 Share Posted November 8, 2007 On first encounter this question, which has been showing up all over the Net, seems inane because the answer seems so obvious. However, as with the infamous Monty-Hall-three-doors-and-one-prize-problem (see The Straight Dope: "On Let's Make a Deal" you pick Door #1, 02-Nov-1990), the obvious answer is wrong, and you, Berj, are right--the plane takes off normally, with no need to specify frictionless wheels or any other such foolishness. You're also right that the question is often worded badly, leading to confusion, arguments, etc. In short, we've got a topic screaming for the Straight Dope. First the obvious-but-wrong answer. The unwary tend to reason by analogy to a car on a conveyor belt--if the conveyor moves backward at the same rate that the car's wheels rotate forward, the net result is that the car remains stationary. An aircraft in the same situation, they figure, would stay planted on the ground, since there'd be no air rushing over the wings to give it lift. But of course cars and planes don't work the same way. A car's wheels are its means of propulsion--they push the road backwards (relatively speaking), and the car moves forward. In contrast, a plane's wheels aren't motorized; their purpose is to reduce friction during takeoff (and add it, by braking, when landing). What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly. A thought experiment commonly cited in discussions of this question is to imagine you're standing on a health-club treadmill in rollerblades while holding a rope attached to the wall in front of you. The treadmill starts; simultaneously you begin to haul in the rope. Although you'll have to overcome some initial friction tugging you backward, in short order you'll be able to pull yourself forward easily. As you point out, one problem here is the wording of the question. Your version straightforwardly states that the conveyor moves backward at the same rate that the plane moves forward. If the plane's forward speed is 100 miles per hour, the conveyor rolls 100 MPH backward, and the wheels rotate at 200 MPH. Assuming you've got Indy-car-quality tires and wheel bearings, no problem. However, some versions put matters this way: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." This language leads to a paradox: If the plane moves forward at 5 MPH, then its wheels will do likewise, and the treadmill will go 5 MPH backward. But if the treadmill is going 5 MPH backward, then the wheels are really turning 10 MPH forward. But if the wheels are going 10 MPH forward . . . Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed. Nonsense. The question thus stated asks the impossible -- simply put, that A = A + 5 -- and so cannot be framed in this way. Everything clear now? Maybe not. But believe this: The plane takes off. airplane airplane 2 Quote Link to comment Share on other sites More sharing options...
ltr450rider Posted November 8, 2007 Share Posted November 8, 2007 Ok peeps here it is... IF the planes engines are off it will only go backwards, roll the tires and not take off. IF the engines are on the tires will turn and the plane will stay in place untill the engines propel it to take off AIR speed. It doesnt say whether they are on or off!!! It doesnt matter weather the engines are on or off. Take off speed,.......is the speed of the air,.......the plane is traveling through. Quote Link to comment Share on other sites More sharing options...
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