Mar 21, 2006
How can you be sure it won't take off? Have you tried it??
Hey just had an idea - Brainiac on sky one!
The "I can do science me" bit.
I think someone should type up a letter and have everyone digitally sign it from all the forums that this post has went on. Then see if we can try it out for real.
I would have suggested MythBusters of the Discovery Channel but that guys tash is wrong and they are far to camp for me. Science'y things should be manly and braw!
I don' have to, I know it wouldn't take off.
You state in your previous post that thrust has no relevance, but in the original question, it suggests that when the plan fires up it's engines, the plane moves forwards, which I would presume is some sort of thrust - correct?
Now if the plane is moving, there's obviously some sort of airflow going over the wings, how fast will it be moving is another question of course... the confusing bit is the conveyor belt applying opposite force to prevent the plane from moving, so friction is the only force stoping movement, but we all know most planes free wheel, so whats stopping the plane from taking off??
Just my theory of course
The aircrafts wings are no moving through air so no air is flowing over them.
The fact that the plane's wheels are moving due to forward thrust is irrelevant. Wheels on a plane are simply there to reduce the amount of friction an aircraft must overcome to gain forward motion. The forward motion is required to get air passing over the aerofoils (wings).
Newton's First Law of Motion applies. The thrust in this case is negated by the treadmill effect of the runway. Equilibrium is reached and there is no forward motion over all.
The fact remains no air is passing over the wings means there is no change in air density or pressure and therefore no lift is created.
Andy, you're getting all confused mate. As I've said earlier, the answer is that a converor belt runway is not 'capable' of preventing the thrust of the engines moving the plane moving forward and thus producing the required lift!
Engines do not provide lift unless they have a combined thrust to weight ratio of greater than 1:1. So that's enough lift to move the combined weight of the engine/s and aircraft as a whole. Even then it would have to be stood on its arse and point nose to the sky; vertical.
In the horizontal engines, no matter how powerfull, do not create lift. No lift, no flight.
Don't make me start quoting Relativity.
errrrr........ it's a trick question, but a more detailed explanation is among these pages. The plane would take off!!
I don't know where the smilies are, otherwise I'd do a big grin.
Ok, you're sstanding at the side of the runway watching this, i.e. you're not part of the conveyer belt system. Is the aircraft moving relative to you?
I'm with JPO on this one, re-read the question Andy, it is suggested that the plane is in motion when the engine fires up! so yes, the aircraft will be moving if we were to be standing on the side of the runway watching it.
What's the point in the treadmill/conveyor then?
Thats the trick bit, it's not actually a trick question as such, more of a 'it wouldn't actually work in the real world' type question.
Some have said the wheels and conveyor belt would go straight to infinity if the plane was to move an inch, but I'm no expert in that field, I'm just stating facts.
Im really not bothered Einstein, as all i know is that if i had been sat on this plane for months now waiting for it to take off i would have caused a riot trying to get off of it by now and asked for a refund
The 'trick' I guess is that the question infers that the converor belt would be capable of preventing the forward motion of the plane, when in reality it couldn't. But if it could then yes, the plane would not move forward and thus no lift, no take off!
OK I think I have solved it once and for all.
What would happen if the plane were to land on the belt?
Would it just stop dead and the wheels spin? HELL NO!
In reality the belt does counter the forward movement of the plane, it moves nowhere. I promise to post the video of this experiment next week.
therefore the plan is phsyically static with only wheels moving and therfore no wind mass movment over and around wings for lift. as i said b4, ha!
I think I'm going to commit mass murder...............
good god is this still going!!
The aircraft would inch forward, however if the conveyor moves to compensate any forward motion of the aircraft then equilibrium is reached; a rolling road situation (without the tethers).
As previously stated wheels on an aircraft are only there to minimise the amount of friction the craft must over come to gain forward motion and start air passing over the wing.
Netwon: An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
If the forward motion of the wheels is negated by the action of the conveyer belt moving in the other direction at an equivalent rate, the net result is that the body of the craft remains stationary to an observer standing at the side of the runway/conveyor.
Since the aircaft has no velocity in relation to it's surroudings, excluding the runway/conveyor, then the net velocity is zero.
If the value of zero is entered into to lift equation then L = 0, regardless of anyother values.
LOL at all the technical stuff, the aircraft I would have presume would have had jet engines to provide the thrust to move it forwards, so apply full thrust and afterburners or whatever... we should now have a moving plane right? Unless the tyres are stuck to the conveyor belt with superglue4, the conveyor belt is as stiff as solid concrete and all the wheel bearings on the jet are seized, my thoughts is that the aircraft will move and take off!
Unless you are saying that a conveyor belt has the ability to negate any thrust created by the jet engines?!
The aircraft is moving, but only relevant to the runway; not the extended environment around it.
What stops you running off a treadmill and through the wall? Is it the fact that the tread is moving in the opposite direction to your feet which are propelling you forward? You are moving forward, but only relevant to the tread, not to your extended surroundings. You will not feel wind on your face no matter how much you run on a treadmill. The same principle applies to the aircraft.
Another example, you return from the toilets in a train. The bog is at the head of the train which is travelling at 100Mph. You walk at a pace of 3Mph.
Now, the train you’re on is moving in this direction: --->
You are walking in this direction: <---
How fast are you travelling?
To you and your fellow passengers you are only moving at 3Mph in this direction: <---
However, to someone watching from a platform you personally, not the train, would be travelling at 97Mph in this direction: --->
I get what you are saying Andy, with the treadmill example, but the engines on the aircraft are more than likely to be jet engines, which provide thrust to push the aircraft forwards. Surely you can't have an aircraft at maximum thrust sitting still with a conveyor belt going at 500mph+ to counter act the force?
So now you're placing limitation on the conveyor? Isn't that moving the goalposts?
It's like arguing if you put Thrust SSC in a rollingroad could it move forward. Essentially your asking the same thing. The answer is no, it wouldn't.
In pure physics the aircraft will not take off.
Groooooooan........ Andy, unlike a car an aircraft is not driven by its wheels, that is the critical factor! when an aircraft takes off and it's wheels leave the ground it doesn't stop moving forward does it? Hope that helps!
lol i said do the brainiac bit as well
Take some secondary school Physics lessons and come back to me once you have a grip of Newton's Laws of Motion.
I'm done with this thread.
Andy, I find it disappointing that you had to post that pic and be done with the thread, we was just getting started lol.
Anyways, your problem lies with you thinking as a physician(sp?), and applying physics to the question, of course the numbers don't add up? Think outside the box, the engines pushes the aircraft forwards, the wheels just holds it up! The conveyor belt can do what it likes, but it shouldn't(theoretically) effect the aircrafts forward movement.
All in my opinion of course, those who agree with me say aiy.
A4Andy knew he fecked up so did a runner. Shame he didn't read and consider the earlier posts.
I love people who reckon they know it all, insult other people and then go off and sulk. The web wouldn't be the same without them.
Thrust SSC WOULD move forwards on a rolling road because unlike the conveyer belt system the rollers are not powered in the opposite direction, hence do not apply enough negative lateral acceleration to hold it in place. (Just a small amount of drag due to the friction of the tyres driving the rollers round)
IM STILL HERE AND STILL NOT BOTHERED ( smiley face thing but its fo--ing gone )
On a serious note i found A4andys picture highly offensive and rather sick
Agreed. That picture often gets pulled from forums for being offensive. The posters are normally twats.
no a conveybelt used in placeof a runway wouldnt work to launch planes, but that isn't the purpose of the question, if the conveyor belt was 2 miles long the plane would simply take off as normal with the exception of the astronimical extra speed of the wheels......
This is all ignoring that fact thers no way a conveyor belt would keep up with the astronomiacal rate of the the wheel speed increase.....
Think about it
plane speed....0 wheel speed 0
thrust from engine move plane forward regardless of the wheel speed
plane speed 5mph Wheel speed 10
Plane speed still 5mph wheels already doing 10 so trying to compensate for the continued 5pmh forward motion extra 5mph means wheels are doing anther 10 mph increase meaning wheels speed now 20mph and so on and so forth, so even is the plane continues doing any speed at all, the conveyer belt will feedback on itself and explode! Even if the conveyor belt could do that the wheel bearing would go out with their rated speed and cease causing the plane to be force backwards probably ripping the indercarriage off. )
So realistically yes the plane will probably take off because the caonyayer belt coulne keep up anyway..... But hypothetically the wheels would cease and it would all go pete tong.......
Oh no, i've loaded the gun again.
Bang...... This isnt what I planned to do today... lol
yep..... But.... the slower the planes acceleration and the higher the take off speed the higher the wheels rate of accerleration(cos of the belt) and ultimately final wheel speed..... Everyon follow that lol
a plane wheel doing 600 mph will probably be well over the wheel bearing rated working capability.......lol.....
thus seizing and destroying the wheel and sending the plane skidding along the conveyer belt at a relative speed of 600mph until the belt realises there is no wheel speed anymore stops dead and then the planes only skidding along at it s real speed........ probably sideways at that point,... possibly in a roll ripping the wings off and fuselage apart...... very pretty...
must be a hell of a ride....
Cant we lock this thread to stop people bringing it back to life.
Separate names with a comma.