Pot Posted October 11, 2008 Share Posted October 11, 2008 Snakes on a treadmill... Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 11, 2008 Share Posted October 11, 2008 With the greatest respect to your dad Pot, who made some (mostly) fine electrical components and iffy hydraulics, no plane uses motorised wheels to get it moving on a takeoff run, the weight penalty would be massive. Also the argument is based on the fact that the treadmillis moving under the planes wheels towards the rear, no-one is debating that if the plane was on the treadmill and it was moving the plane forward that it would eventually take off given time and distance On the takeoff run assistance front I stand ready to be corrected Quote Link to comment Share on other sites More sharing options...
Homer Posted October 11, 2008 Share Posted October 11, 2008 You just had to bring this one back Michael It's a superb example of incorrect theories applied to an ill-stated situation. We all know the plane would take off provided the tread mill is long enough and that it's moving without friction factors applied to the contact area between the tyre, treadmill and wheel bearings. What I would really like to see is someone try to explain the two envelopes probability pradox Quote Link to comment Share on other sites More sharing options...
Branners Posted October 11, 2008 Share Posted October 11, 2008 What I would really like to see is someone try to explain the two envelopes probability pradox is that the one where the chance of finding 2 envelopes in the stationery cupboard are almost none, even though the company orders 1000 a month? Quote Link to comment Share on other sites More sharing options...
OhGod Posted October 11, 2008 Share Posted October 11, 2008 two envelopes probability pradox See, now that one's easy. You just need to round up a bunch of really clever people, and put them together in a room, and then once they're all arguing over it, you can nick both envelopes of cash and leg it while no one is looking. Quote Link to comment Share on other sites More sharing options...
Dave17 Posted October 11, 2008 Share Posted October 11, 2008 Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 11, 2008 Share Posted October 11, 2008 is that the one where the chance of finding 2 envelopes in the stationery cupboard are almost none, even though the company orders 1000 a month? I find it's more Pencil sharpeners, the cupboard says that they should be there, but I've never seen one. Quote Link to comment Share on other sites More sharing options...
Homer Posted October 11, 2008 Share Posted October 11, 2008 is that the one where the chance of finding 2 envelopes in the stationery cupboard are almost none, even though the company orders 1000 a month? Nope, it's a different one. It's where probability predicts that if you are given a choice of two envelopes (one with X amount of £, the 2nd with twice the amount of money), then presented with the opportunity to swap the envelopes, you stand a higher chance of getting a larger amount. Logic says it's 50/50, mathematics says different There is a logical answer, but most don't get it. Same as the plane/treadmill thing. Both of these circumstances were presented in one of my 2nd year mathematics modules at uni, plus many more less "popular" ones. Anyone else want to hear those? I suspect not Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 11, 2008 Share Posted October 11, 2008 Now that must be worth it's own thread. Quote Link to comment Share on other sites More sharing options...
extendor Posted October 11, 2008 Share Posted October 11, 2008 Films = The Running Man, Treadmill (there really is!), Reach for the Sky and no doubt a few more on google if I could be bothered. Quote Link to comment Share on other sites More sharing options...
Gazboy Posted October 11, 2008 Share Posted October 11, 2008 Logic says it's 50/50, mathematics says different It's saturday nght, we are all in, talking to people on the net... ...go on then Homer, explain this one further please. Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 11, 2008 Share Posted October 11, 2008 I'm not in, I'm at work.. The guy I'm working with is boring and I think a closet gay... You lot are the closest to friends I have at the moment. Quote Link to comment Share on other sites More sharing options...
Homer Posted October 11, 2008 Share Posted October 11, 2008 It's saturday nght, we are all in, talking to people on the net... ...go on then Homer, explain this one further please. It's Saturday night, I can't be bothered so would rather see anyone that can be bothered discuss it. It wouldn't welcome an intelligent discussion if the question and supposed answer were provided within a few minutes of each other Maybe it's a bit too far for this forum, but the question is this: You have a choice of two envelopes, one has X amount of pounds, the 2nd has twice the amount of money. You chose one envelope, but the using probability you have a greater chance of getting a larger sum of money by swapping the envelope for the one you didn't choose. That’s the paradox. Edit - In hindsight, you'll need a basic understanding of mathematics to figure out why it's a paradox.. sorry, possibly the wrong audience, but it's the same thing as the plane on a treadmill Quote Link to comment Share on other sites More sharing options...
extendor Posted October 11, 2008 Share Posted October 11, 2008 Ref the envelopes - With my luck I can guarantee I always get the one with the least amount in. Is luck a factor. Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 12, 2008 Share Posted October 12, 2008 Schrodingers cat, now thats a fooked up theory! Quote Link to comment Share on other sites More sharing options...
chilli Posted October 12, 2008 Share Posted October 12, 2008 I may have missed something in this thread, but whats the talk about infinite treadmills. Aren't all treadmills "infinite" by the simple fact that it's a loop going round and round forever Edit - In hindsight, you'll need a basic understanding of mathematics to figure out why it's a paradox.. sorry, possibly the wrong audience, but it's the same thing as the plane on a treadmill I vaguely remember understanding this paradox before, whilst I'm too tired to recall the detail - I'm not sure how it's even slightly similar to the plane on a treadmill (which is actually really straightforward but with a misleading "red-herring" for the easily distracted!). Edit: reminding myself what that paradox is http://en.wikipedia.org/wiki/Two_envelopes_problem and that it's not a real paradox as such in the sense of a fundamental contradiction but rather a paradox caused by the misleading result obtained by analysing the problem in a certain way - I think I see what you mean in that it's somewhat analogous to the plane on a treadmill problem. Both appear paradoxical but in fact with correct analysis, neither are at all right, that's enough of paradoxes for one night, I'm too tired to muster any effort required to think. Quote Link to comment Share on other sites More sharing options...
DamanC Posted October 12, 2008 Share Posted October 12, 2008 It's Saturday night, I can't be bothered so would rather see anyone that can be bothered discuss it. It wouldn't welcome an intelligent discussion if the question and supposed answer were provided within a few minutes of each other Maybe it's a bit too far for this forum, but the question is this: You have a choice of two envelopes, one has X amount of pounds, the 2nd has twice the amount of money. You chose one envelope, but the using probability you have a greater chance of getting a larger sum of money by swapping the envelope for the one you didn't choose. That’s the paradox. Edit - In hindsight, you'll need a basic understanding of mathematics to figure out why it's a paradox.. sorry, possibly the wrong audience, but it's the same thing as the plane on a treadmill The Monty hall problem This may help cXqDIFUB7YU& Quote Link to comment Share on other sites More sharing options...
Pot Posted October 12, 2008 Share Posted October 12, 2008 With the greatest respect to your dad Pot No worries... who made some (mostly) fine electrical components and iffy hydraulics Designed please, the factory staff made the parts you're (mostly) referring to, and can you clarify your 'iffy' comment? no plane uses motorised wheels to get it moving on a takeoff run, the weight penalty would be massive. I've e-mailed him for clarification on this point Also the argument is based on the fact that the treadmillis moving under the planes wheels towards the rear, no-one is debating that if the plane was on the treadmill and it was moving the plane forward that it would eventually take off given time and distance I can see what you said there, but then that would be a treadmill not acting as a treadmill usually would... lol - I believe it's a generic treadmill of infinite length, no friction... On the takeoff run assistance front I stand ready to be corrected I'll see what he says... Quote Link to comment Share on other sites More sharing options...
Scott Posted October 12, 2008 Share Posted October 12, 2008 The paradox question is in the movie "21", although it uses a gameshow as the explanation. I'm pretty inquisitive with things like that so i read up on it a bit after watching the movie. Its a cracking maths problem and even though it makes no sense when you say it, when you go through the problem it all becomes clear. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 12, 2008 Share Posted October 12, 2008 I can see what you said there, but then that would be a treadmill not acting as a treadmill usually would... lol - I believe it's a generic treadmill of infinite length, no friction... I think in the original problem the treadmill was motorised/powered, meant to be to counteract the forward momentum of the engine. A lot of people assume that if the plane was moving forward at 30mph and you turned on the treadmill to move backwards at 30mph the plane would remain stationary. Its not a case of a frictionless treadmill where, with a car, it would counteract the wheels turning keeping it in the one place. Although, the same answer would be given to this problem as even when frictionless, as you said, the wheels wouldn't move the plane would just continue forward moving the treadmill with it. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 12, 2008 Share Posted October 12, 2008 But what if the treadmill was designed to equal the force of the 747's engines? The plane would still take off if the treadmill had the same force... but... if it could create the same amount of force in friction to the wheels as the engines then it could stop the plane from taking off. All theoretical though as the stresses and strains would be impossible. Quote Link to comment Share on other sites More sharing options...
tbourner Posted October 12, 2008 Share Posted October 12, 2008 Oh, and he also commented, it'd fall of the end of the treadmill, so his answer's after I told him it's a treadmill of infinite length... Why would it fall off the end? I'd always assumed the treadmill was the length of the runway, rather than being infinite. What about the problems with the wheel bearings on your average plane only being tested up to 1.5 times the planes take off speed? They might fall apart, then the plane wouldn't take off!! Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 12, 2008 Share Posted October 12, 2008 Is it possible to drive onto the back of a lorry, as in knightrider, without shooting through the back of it? And as if by magic thats on Mythbusters this morning! Quote Link to comment Share on other sites More sharing options...
tbourner Posted October 12, 2008 Share Posted October 12, 2008 Edit: reminding myself what that paradox is http://en.wikipedia.org/wiki/Two_envelopes_problem and that it's not a real paradox as such in the sense of a fundamental contradiction but rather a paradox caused by the misleading result obtained by analysing the problem in a certain way - I think I see what you mean in that it's somewhat analogous to the plane on a treadmill problem. Both appear paradoxical but in fact with correct analysis, neither are at all It's just a case of bad maths though surely? They're simplifying the equation too much. The Monty hall problem cXqDIFUB7YU& Same thing isn't it? Switching the maths to make it sound like a better choice. Surely after effectively removing one of the choices, sticking with door one or switching to door two both offer a 50% chance of getting the car, it's not 33.3% to stick with door one and 66.7% to switch - it's a new question with new factors, you can't just keep the original question's statistics!! Quote Link to comment Share on other sites More sharing options...
tbourner Posted October 12, 2008 Share Posted October 12, 2008 Is it possible to drive onto the back of a lorry, as in knightrider, without shooting through the back of it? If you are travelling at 40mph and the lorry is doing 30, when you get into the lorry what speed will you be doing? Velocity is a function including force and mass though, the force available driving the car isn't enough to propell the mass of the car (with respect to the Earth, not the lorry) from 40 to 70 mph in the space of a few centimetres. All that would happen is a bit of squealing from the wheels, you'd be doing somewhere between 30 and 40mph (with respect to the Earth), and you'd drive up onto the lorry and be fine. The real issue is getting the gear change right, or deciding when your autobox will give up! Quote Link to comment Share on other sites More sharing options...
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