sundevil777 94 #76 January 3, 2006 Please understand that the original problem statement in this thread is misleading. I'm making this conclusion from the link PilotDave provided (see post 37): http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=2006441#2006441 It is the speed of the plane (body of the plane) that will be matched by the conveyor. The speed of the plane and speed of the conveyor should be considered to be the speed relative to the ground. This means that when the plane is going 10mph forward, the conveyor will be going 10mph backward, so the wheels will be spinning at 20mph. This will have the effect of some extra friction from the wheels, and that is all. It does NOT meant that the conveyor is defined so that it moves in a way to keep the plane still relative to the ground. We all know that air moving over the wings is what makes lift. Please realize this fundamental difference. The plane will take off with a little extra conveyor/runway length required.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
Broke 0 #77 January 3, 2006 You know what upon furhter consideration I would ahve to change my anwer. Yes it will take off. For one of the reasions I stated previously, and from that message board. However the conveyor belt wouldn't change the runway lenght. Because it would still need to generate the airspeed necessary to lift off.Divot your source for all things Hillbilly. Anvil Brother 84 SCR 14192 Quote Share this post Link to post Share on other sites
champu 1 #78 January 4, 2006 I'm sorry, I answered the question as it was asked in this thread as opposed to changing the question to what I thought the person was trying to ask, and then answering it. How silly of me. QuoteThe conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. This is not a stable control system, it doesn't matter WHAT you put on this conveyor, I don't care if it's a skateboard with a desk fan on it, an airplane driven by the thrust of it's engines, or a fat guy on roller skates that the almighty himself fucking miracles forward, as soon as whatever it is tries to move, the conveyor will accelerate out of control. /edited to add: QuoteIt is the speed of the plane (body of the plane) that will be matched by the conveyor. This is, indeed, a COMPLETELY different question, and not even really an interesting one as far as I'm concerned. Quote Share this post Link to post Share on other sites
Steeler 0 #79 January 4, 2006 The plane will not take off. That is my final answer. Quote Share this post Link to post Share on other sites
godfrog 2 #80 January 4, 2006 the plane would roll right off the conveyor because the power is not supplied to the wheels, if the conveyor moved it would be in the same direction of the plane because of the friction of the wheels dragging on the surface. I.E. if all of the cars in the world pointed the same way and all accelerated at the same time could they change the earths rotation?Experience is a difficult teacher, she gives you the test first and the lesson afterward Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #81 January 4, 2006 QuoteImagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. There is no wind. Can the plane take off? Joe If I understand the problem, the plane is going to be accelerating via its engines, but the wheels won't spin on their axles because the conveyer is going to move in the direction of takeoff as fast as the wheels would want to roll? Sure, the plane would get airborne. What the wheels are doing doesn't enter into it. Now, to read the rest of the thread that followed the first three posts, to see how much this has been hashed out... -Jeffrey-Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #82 January 4, 2006 Quote A few WWII rocket and jet powered aircraft used this, including some kamikaze aircraft. (No need for landing gear!) Must have been really creepy/weird/sick to design and/or build such an airplane. I know that their culture is utterly different from ours, but imagine an American worker in a factory working on a plane that he and everyone else knew was intended to be a death machine piloted by a living human who was intentionally going to crash and die. People say you can't judge a culture from within your own, and outside of theirs. I say HELL YES you can, and that's one friggin' sick culture. I guess they're "different" nowadays, though. -Jeffrey-Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
godfrog 2 #83 January 4, 2006 what the ground does is totally irrelevant to an airplane, takeoff or otherwise. this is why a float plane can take off of a river, upstream or down stream. all it takes to fly is air speed.Experience is a difficult teacher, she gives you the test first and the lesson afterward Quote Share this post Link to post Share on other sites
wildblue 4 #84 January 4, 2006 QuoteThis is, indeed, a COMPLETELY different question, and not even really an interesting one as far as I'm concerned. What he said. it's like incest - you're substituting convenience for quality Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #85 January 4, 2006 Believe me, as a private pilot, I understand that. I just read one of the more recent posts (top of this page) and as I understand it, we're now supposed to think of the conveyor belt as rolling in the same direction as the wheels, so as to nullify the forward travel of the plane relative to the rest of the surroundings. This is tricky, but won't happen. The thrust is coming from the prop/jet. The plane will start to roll forward relative to the environment. The conveyor belt will start to roll with the wheels, but cannot stop the plane from pushing itself forward. This is because the forward travel of the plane is NOT dependent on [I]drive from the wheels. This is not the same as a car that has all four wheels on a conveyor belt or dynamometer. All the conveyor belt will do is slow the plane's acceleration by the same figure as the friction of the wheel assembly is responsible for producing. -Jeffrey-Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
gmittar 0 #86 January 4, 2006 Wow, so simple a question, wtf is there 4 pages of posts for? Lift off is determined by airflow over wings, and angle of attack of wings, kk? Conveyer belt = no airflow = no liftoff unless the conveyer suddenlty shoots the plane off the end or some such shit. Opposite, put a plane on the ground in a wind tunnel, and crank up the wind, it'll take off. (no, not a skydiving wind tunnel, silly) |>.<| Seriously, W.T.F. mate? Quote Share this post Link to post Share on other sites
popsjumper 2 #87 January 4, 2006 No. The plane is not moving. No wind speed, no lift.My reality and yours are quite different. I think we're all Bozos on this bus. Falcon5232, SCS8170, SCSA353, POPS9398, DS239 Quote Share this post Link to post Share on other sites
sundevil777 94 #88 January 5, 2006 QuoteNo. The plane is not moving. No wind speed, no lift. Yes, the plane can move. The conveyor belt is not intended to keep the plane stationary relative the the ground. Only to move the opposite direction of the plane, at the same speed as the plane, both speeds measured relative to the ground. The wheels of the plane will go twice the speed of the plane (speed of plane plus speed of conveyor), so there will be a little bit of extra friction for the plane to overcome. Maybe the only thing this 'riddle' shows is that people naturally want to come to the conclusion that the plane can't move forward. The speed of the conveyor and speed of the plane can be identical and in opposite directions, and still have the plane moving relative to the ground because the wheels roll.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
sundevil777 94 #89 January 5, 2006 QuoteI just read one of the more recent posts (top of this page) and as I understand it, we're now supposed to think of the conveyor belt as rolling in the same direction as the wheels, so as to nullify the forward travel of the plane relative to the rest of the surroundings. No, that is not the problem statement. Pilotdave posted the link to the physics forum. The problem statement there is much clearer than how it was mis-described at the beginning of this thread by BoostedXT. http://forum.physorg.com/index.php?showtopic=2417&st=0 It is the speed of the 'plane', not the wheels/rotating point on the wheels or anything that might be confusing about using some point on the wheels. Also, there is nothing to keep us from defining the speed of the conveyor and plane as relative to the ground. It would have been nice for this to be stipulated in the problem statement, but maybe it would be less fun for those that design such mind teasers, because people would get it quicker, and not be tempted to think the plane can't move, can't get airspeed.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #90 January 5, 2006 It's maddening how some of you people just won't get this. The plane's jets are pushing against the AIR. The wheels don't matter unless something locks them. Once the jets start moving the plane forward, the wheels will roll forward. If the conveyor belt were to run toward the tail of the plane, the wheels would speed up their revolutions but the plane would move freely forward (impeded only by the friction of the wheels on their axles and other wheel-related friction). If the belt ran toward the nose of the plane, it would keep the wheels from moving at all if it matched the jet-powered accelleration of the plane; slower, the wheels would appear to roll forward at some speed slower than the plane's jet-powered progress; faster, and the wheels would appear to roll backward. Is there some definitive, "this-is-what-the-book-in-which-this-question-appeared" answer to this thing forthcoming? -Jeffrey-Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
sundevil777 94 #91 January 5, 2006 QuoteIt's maddening how some of you people just won't get this. Maybe you didn't intend to reply to my post. I agree, it would be able to take off.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
champu 1 #92 January 5, 2006 QuoteIs there some definitive, "this-is-what-the-book-in-which-this-question-appeared" answer to this thing forthcoming? The way this thread is going, I'd just like to have a definitive QUESTION. It's as if someone walked into the thread and asked what time it was. And I answer "it's 6pm" and then someone else jumps in and says, "no it's not, it's Wednesday." and I ask the second person what they're talking about, and they say, "well the original poster didn't really phase the question right, they should have asked what day of the week it is, and it's Wednesday." Meanwhile five other people are going on about, "leap years happen every four years, but that it's all a trick question because 2000 wasn't a leap year. I can't believe how many idiots don't know that." Quote Share this post Link to post Share on other sites
Lindercles 0 #93 January 5, 2006 actually, what's really important here is that there was a leap second at the end of 2005. Apparently the earths conveyor belt experiences a bit of friction and can't keep up with our clocks. See, the earth's rotation speed is not necessarily equal to the ground speed through space. And I'm sure all of our planes taking off doesn't help. Quote Share this post Link to post Share on other sites
champu 1 #94 January 5, 2006 Nah, the earth doesn't get its rotation from its conveyor belt, the friction there is negligible. This is obviously a tidal problem. /edit: agh! it's vs. its Quote Share this post Link to post Share on other sites
sundevil777 94 #95 January 5, 2006 Maybe the earth's rotation slowing is the real cause of global warming, and there isn't anything we can do about it, Kyoto treaty and all. People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
Steeler 0 #96 January 5, 2006 Ok, the way I understood the original question was that since the conveyor is MATCHING wheel speed, that means the wheels CANNOT turn faster than the conveyor. Which means the plane will not be able to move forward relative to its environment, which means no airflow over wings. Quote Share this post Link to post Share on other sites
godfrog 2 #97 January 5, 2006 maybe the earth is rotating faster and pretty soon we will all flt off the ground and we will have to get a chute out to slow down so that damn plane can come get use if someone can get it off the ground:Experience is a difficult teacher, she gives you the test first and the lesson afterward Quote Share this post Link to post Share on other sites
sundevil777 94 #98 January 5, 2006 No no no! The earth is slowing. Damn, that means our weight is increasing! People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
Lindercles 0 #99 January 5, 2006 QuoteDamn, that means our weight is increasing! I'm seeing the next McDonald's ad campaign here. Quote Share this post Link to post Share on other sites
ematteo 0 #100 January 5, 2006 I agree. The original question states that the conveyor moves at the same speed as the *wheels*. Another way of looking at this is: if you lock a plane's wheels and stop them from rotatingat all, then run up the engines to full thrust, will the plane take off? Only if the tires slide reallly fast... My answer to the question, as written, is no. No takeoff (so the MIT vote is split). If the question was changed to match the plane's groundspeed (measured by GPS, perhaps) to the conveyor, then yes, it could take off. Just like having a tailwind, the wheels turn twice as fast but you still move. This is the difference between the question posted at the beginning of this thread and the one referenced in a link above. Quote Share this post Link to post Share on other sites
