Gaz6002 Posted February 6, 2008 Share Posted February 6, 2008 Only if you were pushing from the treadmill... But you will be as the force is transferred through the wheels via gravity. ^^^^Newtons law again. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 6, 2008 Share Posted February 6, 2008 nope thats no it http://en.wikipedia.org/wiki/Newton's_laws_of_motion Quote Link to comment Share on other sites More sharing options...
Matt H Posted February 6, 2008 Share Posted February 6, 2008 Its the laws of relativity that i was refering too Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 6, 2008 Author Share Posted February 6, 2008 So if your mate was running on a treadmill and you stood on the ground behind.. If he was on rollerskates and you held his back, he would stay in place? If you then pushed forwards, he would move forwards regardless of the speed of the treadmill. Quote Link to comment Share on other sites More sharing options...
Matt H Posted February 6, 2008 Share Posted February 6, 2008 http://en.wikipedia.org/wiki/Newton's_laws_of_motion whats that got to do with what happens when matter gets up towards the speed of light?! Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 6, 2008 Share Posted February 6, 2008 So if your mate was running on a treadmill and you stood on the ground behind.. If he was on rollerskates and you held his back, he would stay in place? If you then pushed forwards, he would move forwards regardless of the speed of the treadmill. Yes but the treadmill in this instance compensates for the push... hence no, you wouldn't move. Quote Link to comment Share on other sites More sharing options...
Thorin Posted February 6, 2008 Share Posted February 6, 2008 Yes. Because every time you push the car the treadmill speeds up. Never-ending battle until the wheels fall off. Alright then think of it this way... Place car on treadmill holding your finger at the back of it. Start the treadmill moving. Your finger is at the back of the car stopping it from rolling backwards off the treadmill, so it stays still. Accelerate the treadmill to whatever speed you like, the wheels are free moving and will just go round faster, the car will remain stationary as your finger is in place to stop it. Will the treadmill stop you from pushing the car forward instead of just holding it still? Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 6, 2008 Author Share Posted February 6, 2008 Yes but the treadmill in this instance compensates for the push... hence no, you wouldn't move. You'd still move him even if the treadmill sped up. Quote Link to comment Share on other sites More sharing options...
Rob Posted February 6, 2008 Share Posted February 6, 2008 ITS NOT A CAR THE ENGINES/PROPELLER ACT ON THE AIR How does a plane normally accelerate down a runway for crying out loud, a moped engine on each wheel? I despair. You despair??? I'm genuinely disappointed in the level of intelligence from members, shown in this thread, and on top of that it's been around the internet for years. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 6, 2008 Share Posted February 6, 2008 Thorin is spot on. If you were running at 7mph on a treadmill in a gym and had a jetpack on your back with a forward thrust capability of 100mph, bit like a plane, and whacked it up to the full 100mph suddenly, do you a) rocket off messily through the wall at 100mph, or b) note the treadmill now reads 107mph Right, while despairing, I thought up a great analogy. Don't bring into this friction or tyres exploding or minimum air speeds or anything as that's just silly side issues, it's a hypothetical thought experiment. Now, one of the best ways to think about if something behaves a certain way or not is to try the theory in different scenarios, so we'll have the plane land on a treadmill instead... Most of you state this is true: "A plane can't take off if the runway underneath acts like a treadmill, i.e. you push against it and it moves backwards. The plane will remain stationary no matter what thrust the pilot asks of the engines." I think that's a fair summing up. So the important thing here is - if the runway goes in the opposite direction at the same speed the plane will be stationary. That means if a plane flys at zero feet altitude at 300mph and touches down on a normal runway, the plane continues at 300mph and the wheels turn at 300mph. If the plane flys at zero feet altitude at 300mph and touches down on a runway going 300mph in the opposite direction, your statement about the plane's behaviour on a treadmill is that it will immediately stop dead because the treadmill cancels out the plane's forward speed Or, my theory says, the wheels just chirp almightily as spin at 600mph as the plane carries on it's merry way unaffected. If it then accelerates up to 400mph, the wheels go at 800mph as the treadmill goes 400mph backwards but the plane STILL ACCELERATES MERRILY ON ITS WAY. Other than that, I give up Watch mythbusters if you need the all-knowing telly to hammer it home. I'm frankly shocked at how this thread is panning out. -Ian PS I haven't seen the mythbusters episode, I'm that confident I'm right. I just tried to get a £1000 bet out of someone who was adamant it'd sit still, alas, they didn't have the conviction of their own argument Quote Link to comment Share on other sites More sharing options...
Thorin Posted February 6, 2008 Share Posted February 6, 2008 Thorin is spot on. I should have been a mod you know Quote Link to comment Share on other sites More sharing options...
heckler Posted February 6, 2008 Share Posted February 6, 2008 ok I grabbed this off another forum, but it invoked several different ideas.. Lets try it with you guys... A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off and why? Don't run off and Google, but I'll let you know that Mythbusters tried this.. But lets see what you think first... Its a harrier, takes off verticly Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 6, 2008 Share Posted February 6, 2008 Its a harrier, takes off verticly Ah but what if you have a small treadmill set vertically against one of it's wheels, set to go down as fast as you try to go up? Quote Link to comment Share on other sites More sharing options...
redtwinturbo Posted February 6, 2008 Share Posted February 6, 2008 ^ yeah that, (Ian C's long post about landing) I typed a long reply out but this was far better than mine anyway Quote Link to comment Share on other sites More sharing options...
spidermonkey Posted February 6, 2008 Share Posted February 6, 2008 Thorin is spot on. If you were running at 7mph on a treadmill in a gym and had a jetpack on your back with a forward thrust capability of 100mph, bit like a plane, and whacked it up to the full 100mph suddenly, do you a) rocket off messily through the wall at 100mph, or b) note the treadmill now reads 107mph Right, while despairing, I thought up a great analogy. Don't bring into this friction or tyres exploding or minimum air speeds or anything as that's just silly side issues, it's a hypothetical thought experiment. Now, one of the best ways to think about if something behaves a certain way or not is to try the theory in different scenarios, so we'll have the plane land on a treadmill instead... Most of you state this is true: "A plane can't take off if the runway underneath acts like a treadmill, i.e. you push against it and it moves backwards. The plane will remain stationary no matter what thrust the pilot asks of the engines." I think that's a fair summing up. So the important thing here is - if the runway goes in the opposite direction at the same speed the plane will be stationary. That means if a plane flys at zero feet altitude at 300mph and touches down on a normal runway, the plane continues at 300mph and the wheels turn at 300mph. If the plane flys at zero feet altitude at 300mph and touches down on a runway going 300mph in the opposite direction, your statement about the plane's behaviour on a treadmill is that it will immediately stop dead because the treadmill cancels out the plane's forward speed Or, my theory says, the wheels just chirp almightily as spin at 600mph as the plane carries on it's merry way unaffected. If it then accelerates up to 400mph, the wheels go at 800mph as the treadmill goes 400mph backwards but the plane STILL ACCELERATES MERRILY ON ITS WAY. Other than that, I give up Watch mythbusters if you need the all-knowing telly to hammer it home. I'm frankly shocked at how this thread is panning out. -Ian Very well put, i think it is the way the initial question has been asked, ie the treadmill being able to compensate for motion, this would not really be possible in real life terms, i have really enjoyed this thread, and i believe that are some very clever people on here that have stated good arguments without too much google, i will follow this up when i get home Quote Link to comment Share on other sites More sharing options...
Thorin Posted February 6, 2008 Share Posted February 6, 2008 Its a harrier, takes off verticly Ah but what if you have a small treadmill set vertically against one of it's wheels, set to go down as fast as you try to go up? Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 6, 2008 Author Share Posted February 6, 2008 Other than that, I give up Watch mythbusters if you need the all-knowing telly to hammer it home. I'm frankly shocked at how this thread is panning out. I thought it'll all me tied up by now... God I'm enjoying this. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 6, 2008 Share Posted February 6, 2008 I'm honestly stuggling to understand this your reasoning behind this? How can the forces be put together to create lift in this situation? Quote Link to comment Share on other sites More sharing options...
heckler Posted February 6, 2008 Share Posted February 6, 2008 Ah but what if you have a small treadmill set vertically against one of it's wheels, set to go down as fast as you try to go up? assuming the aricraft is on the ground? well if it is it will just sit there with the wheel spining Quote Link to comment Share on other sites More sharing options...
johnnyknox Posted February 6, 2008 Share Posted February 6, 2008 No air is passing over and under the wings to give lift (high/low pressures) etc, plus the engines would overheat too I'd thought. EDIT: So no it won't take off. Just ask supradibbs agreed Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 6, 2008 Author Share Posted February 6, 2008 assuming the aricraft is on the ground? well if it is it will just sit there with the wheel spining What if you turn the treadmill on once it's 20 foot above the ground? Quote Link to comment Share on other sites More sharing options...
Alex Posted February 6, 2008 Share Posted February 6, 2008 I'm honestly stuggling to understand this your reasoning behind this? How can the forces be put together to create lift in this situation? Engine Thrust pushes the plane fwd. The wheels rotate in a reaction to this thrust. The treadmill doubles the speed of the wheels. The mass of the aircraft is still thrusted fwd...upto the AIR speed necessary for the air to be passing over the wing fast enough for liftoff. The wheel speed is still doubled but cannot affect the AIR speed of the plane. The plane is moving through the air relative to the earth, not the tradmill. Quote Link to comment Share on other sites More sharing options...
heckler Posted February 6, 2008 Share Posted February 6, 2008 What if you turn the treadmill on once it's 20 foot above the ground? easy, the harrier can then move away from the treadmill my POV is that the aircraft will take off. as Ian and co have hit the nail on the head, the fact the wheels will effectivly cancel out the movment of the treadmill, and adidtional force i.e. engines will cause the aircraft to start moving forwards eventually taking off. And I am in the RAF Quote Link to comment Share on other sites More sharing options...
supradibbs Posted February 6, 2008 Share Posted February 6, 2008 Thrust pushes the plane fwd. The wheels rotate in a reaction to this thrust. The treadmill doubles the speed of the wheels. The mass of the aircraft is still thrusted fwd...upto the AIR speed necessary for the air to be passing over the wing fast enough for liftoff. The wheel speed is still doubled but cannot affect the AIR speed of the plane. well put the way i understand it is forget the wheels in relation to power the engine creates the power for forward motion (wheels free spin) the movement of the treadmill is doubling the forward speed thus creating enough forward speed to obtain lift Quote Link to comment Share on other sites More sharing options...
Matt H Posted February 6, 2008 Share Posted February 6, 2008 Cant believe people are actually still arguing the toss on this after many great explanations have been provided to give reason as to why the plane does indeed take off. Surely, anyone with have a brain, would so "arrrrr yes" i get it now. Quote Link to comment Share on other sites More sharing options...
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