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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by destinationnovascotia
(Post 5564796)
Now thats more like it. I can relate to this conversation:thumbsup:
Fancy a vodka then - coz then you can really see the fairies - honest. I have lived in Cottingley 20 years, even saw Mel Gibson in the pub once when they filming - REALLY |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by manghams
(Post 5564809)
Fancy a vodka then - coz then you can really see the fairies - honest.
I have lived in Cottingley 20 years, even saw Mel Gibson in the pub once when they filming - REALLY Unfortunately I am at work on the night shift and the patients would probably complain....although maybe if I share... |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by destinationnovascotia
(Post 5564824)
Do you know how much I could go for a vodka.
Unfortunately I am at work on the night shift and the patients would probably complain....although maybe if I share... Might help them sleep - thats what I'm hoping for. :zzz: I think now maybe I should be sharing .... to much of a good thing. :lol: |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by manghams
(Post 5564838)
Might help them sleep - thats what I'm hoping for. :zzz:
I think now maybe I should be sharing .... to much of a good thing. :lol: |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by destinationnovascotia
(Post 5564864)
Sharing is good...that way everyone falls asleep and no one is likely to wake you up early
Except my kids who will be up before 7.30am - maybe I should just do a through; anyway this tread mill thing is frying my brain cells - those that the vodka has left anyway. :beer: Going back to the bar now........ |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by macmike41
(Post 5564548)
If the treadmill is at zero and the plane is at zero then their speed is matched .... no no forget I said that I'm not here I'm going going gone.......
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by destinationnovascotia
(Post 5564446)
I can't believe that this has gone on for so long.
The treadmill matches the speed of the plane, so the plane is moving forward......hear that.........moving forward. Just because the treadmill is moving in the oppposite direction does not change the fact that the plane is moving forward. You will get wing lift as the plane moves forward.....just the wheels will spin really fast as the treadmill moves backwards whilst the plane moves forward. If the plane wasn't moving forward, there would be no speed and the question clearly states that the treadmill goes at the same speed as the plane. 2) I've just spoken to my son in Glasgow Uni ,he is a 3rd year Aerospace engineer. The (theoretical) treadmill is moving backwards at the same speed as the aircraft wheels are moving forward,Obviously the engines are driving the airframe and maintaining it's velocity in relation to the treadmill ,it is however merely "station keeping" the aircraft has no forward ground speed ,and no airflow over the wings.so would not leave the ground. airflow is everything,I have seen a ww2 german spotter plane (storch) fly at zero groundspeed in a 30 mph headwind,it's still doing 30mph airspeed. 3)what was the original question in this thread? |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by tom17
(Post 5554071)
Imagine a plane is sitting on a massive hypothetical conveyor belt, as wide and as long as a runway. The conveyor belt is designed to match the speed of the plane exactly but moves in the opposite direction. The engines are running at take-off thrust, the brakes are off, etc. Everything is normal save for the fact the plane is on a treadmill.
Can the plane take off? Discuss :) Tom... |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by johnnyc
(Post 5566184)
1) I can't believe tthis thread has gone on so long either.!!!!!!!!
2) I've just spoken to my son in Glasgow Uni ,he is a 3rd year Aerospace engineer. The (theoretical) treadmill is moving backwards at the same speed as the aircraft wheels are moving forward,Obviously the engines are driving the airframe and maintaining it's velocity in relation to the treadmill ,it is however merely "station keeping" the aircraft has no forward ground speed ,and no airflow over the wings.so would not leave the ground. airflow is everything,I have seen a ww2 german spotter plane (storch) fly at zero groundspeed in a 30 mph headwind,it's still doing 30mph airspeed. 3)what was the original question in this thread? |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by johnnyc
(Post 5566184)
1) I can't believe tthis thread has gone on so long either.!!!!!!!!
2) I've just spoken to my son in Glasgow Uni ,he is a 3rd year Aerospace engineer. The (theoretical) treadmill is moving backwards at the same speed as the aircraft wheels are moving forward,Obviously the engines are driving the airframe and maintaining it's velocity in relation to the treadmill ,it is however merely "station keeping" the aircraft has no forward ground speed ,and no airflow over the wings.so would not leave the ground. airflow is everything,I have seen a ww2 german spotter plane (storch) fly at zero groundspeed in a 30 mph headwind,it's still doing 30mph airspeed. 3)what was the original question in this thread? . Newtons laws of motion. 3rd law "For every action, there is an equal and opposite reaction." Product of compression and combustion against surrounding air. It would only be stationary if the driving force were the wheels as with a car. Aircraft wheels have no driving mechanism, they rotate freely around the axle, affected only by friction. In this case there are 4 gas turbines producing 57000lbs odd of thrust each under the wings, opposing the air mass behind. This creates movement relative to the airmass. The belt is irrelevant once inertia is overcome and the thrust matches any friction movement of the aircraft by the belt. As thrust increases, the mass (aircraft) will move forward, gathering speed relative to the air mass, once the critical speed is achieved (rotate) the aircraft leaves terrafirma and this confounded belt, never to return to this airfield again. At least the runways I used stood still, well most of them anyway! |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by johnnyc
(Post 5566184)
1) I can't believe tthis thread has gone on so long either.!!!!!!!!
2) I've just spoken to my son in Glasgow Uni ,he is a 3rd year Aerospace engineer. The (theoretical) treadmill is moving backwards at the same speed as the aircraft wheels are moving forward,Obviously the engines are driving the airframe and maintaining it's velocity in relation to the treadmill ,it is however merely "station keeping" the aircraft has no forward ground speed ,and no airflow over the wings.so would not leave the ground. There are versions of this thread in the US forums and Australian forums as well. Please read all of the posts. There are several examples and thought experiments that will demonstrate that the treadmill cannot stop the plane from moving relative to the air around it. You'll see that several people, including at least one physicist, who thought the plane could not take off eventually realized that they were wrong. |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Bill_S
(Post 5567095)
Surrey Expat is correct, and you are wrong. I think I see the error you are making. You are focused on the wheels. The wheels are irrelevant to the drive train of an aircraft. The treadmill cannot cause the plane to "keep station" if the engines are thrusting. If you were trying to drive a car on the treadmill, the movement of the belt could match the speed of the car's wheels and cause the car to "keep station" with the air around it. If the car had wings, the wings would never generate lift because the car would have zero airspeed. The aircraft's engines are not driving the wheels, they are providing thrust. That thrust vector must move the airframe with respect to the air around it, unless the airframe is being retarded by an opposing force vector. Newton's Third Law is the key. The treadmill cannot apply a force vector to the airframe; it can only spin the wheels.
There are versions of this thread in the US forums and Australian forums as well. Please read all of the posts. There are several examples and thought experiments that will demonstrate that the treadmill cannot stop the plane from moving relative to the air around it. You'll see that several people, including at least one physicist, who thought the plane could not take off eventually realized that they were wrong. perhaps this is a job for the mythbusters :) |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by johnnyc
(Post 5568085)
.
perhaps this is a job for the mythbusters :) |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Surrey Expat
(Post 5568227)
There's no myth about it, its pure physics.
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Bill_S
(Post 5568274)
Agreed. No myth, just a free-body problem. In any case, the mythbusters would first do a small-scale test with a toy plane and a fitness club treadmill. That would answer the question immediately.
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