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Message
1
Posted on 4/10/24 at 5:26 pm to cubsfan5150
It's been explained in numerous posts from me and others. Go back and read.
Posted on 4/10/24 at 5:32 pm to LNCHBOX
quote:Your thought process exists within the confines of reality and actual physics.
It's been explained in numerous posts from me and others. Go back and read.
The OP situation implies that the treadmill is moving in the opposite direction fast enough to prevent the forward momentum if the aircraft engines.
At least that is how people are reading it.
If the treadmill moves fast enough to prevent forward momentum of the plane, thus preventing air currents above and below the wings, it will not take off.
Is that actually possible in reality? No.
But the assumption is that the OP does not exist in reality.
Otherwise, it is poorly written.
Posted on 4/10/24 at 5:33 pm to LNCHBOX
quote:
Stick a pencil through a washer. Put the washer on a moving treadmill. Can you move the pencil forward?
Yeah, but at that point the washer is spinning faster than the treadmill.
Let's say I put a jet engine one a car. I'm only applying forward force via the jet engine, not through a drive shaft. I then place that car on a treadmill. I set the treadmill at 30 mph, and then I power up the jet engine to push the car. If the treadmill is 30 mph, and I'm applying enough power to stay in one spot, then my speedometer will read 30 mph. I then power up the jet to push me forward a little. My speedometer now says 35 mph and I'm making forward progress. If the treadmill then speeds up to match that, my forward progress is stopped and I stay in place again.
Posted on 4/10/24 at 5:34 pm to BottomlandBrew
The two groups in this thread involve one that cannot separate the question from actual physics and reality and the other that is looking at it only through the confines of the questions factors.
Posted on 4/10/24 at 5:35 pm to Scruffy
quote:
The OP situation implies that the treadmill is moving in the opposite direction fast enough to prevent the forward momentum if the aircraft engines.
Impossible as the force of teh treadmill is not transmitted to the actual plane.
quote:
At least that is how people are reading it.
People are stupid
quote:
But the assumption is that the OP does not exist in reality.
Even strictly within the confines of what is described, teh plane will move.
quote:
Otherwise, it is poorly written.
It would not takeoff because the runway is too short if we take teh image literally, but it will move without question.
Posted on 4/10/24 at 5:35 pm to BottomlandBrew
If the wheels are moving at the same speed as the treadmill, the only way that plane is getting off the ground is if you put a big enough fan in front of the treadmill to create enough airflow such that the wings get lift. Correct?
Posted on 4/10/24 at 5:36 pm to BottomlandBrew
quote:
Yeah, but at that point the washer is spinning faster than the treadmill.
Let's say I put a jet engine one a car. I'm only applying forward force via the jet engine, not through a drive shaft. I then place that car on a treadmill. I set the treadmill at 30 mph, and then I power up the jet engine to push the car. If the treadmill is 30 mph, and I'm applying enough power to stay in one spot, then my speedometer will read 30 mph. I then power up the jet to push me forward a little. My speedometer now says 35 mph and I'm making forward progress. If the treadmill then speeds up to match that, my forward progress is stopped and I stay in place again.
All you're showing is why the plane will move
Posted on 4/10/24 at 5:45 pm to Hateradedrink
Still waiting on the “it won’t move” crowd to address this
This post was edited on 4/10/24 at 5:47 pm
Posted on 4/10/24 at 5:48 pm to LNCHBOX
quote:I am aware, but the wheels are there to reduce friction and allow for the plane to move forward.
Impossible as the force of teh treadmill is not transmitted to the actual plane.
The wheels still have a relationship with the treadmill and will react to its actions.
quote:
Even strictly within the confines of what is described, teh plane will move.
If you put a jet engine with wheels on a treadmill, and the engine has a max speed of, say, 800 mph, and the treadmill is moving at the exact same speed in the opposite direction, 800 mph, your stance is that the jet engine would move forward?
I’m assuming that the implication here is that thrust is strictly linear without any lift being applied by the engines.
Maybe I’m just stupid.
Is the argument that the contact point between the tires and ground essentially become as close to frictionless and possible at increasing speeds?
This post was edited on 4/10/24 at 5:53 pm
Posted on 4/10/24 at 5:54 pm to Street Hawk
Anyone saying yes needs to meet a man named Bernoulli
And we all know y’all didn’t spend anytime in CEBA.
And we all know y’all didn’t spend anytime in CEBA.
This post was edited on 4/10/24 at 5:55 pm
Posted on 4/10/24 at 6:13 pm to Scruffy
quote:
Is the argument that the contact point between the tires and ground essentially become as close to frictionless and possible at increasing speeds
Doesn't really matter if the contact point is frictionless thereby negating forward movement. A conveyor that wide and long, moving at speed, would pull in enough air moving across the upper and lower surfaces of the wings to create lift. This would then cause the plane to take off.
Posted on 4/10/24 at 6:15 pm to Street Hawk
No, the plane would not be able to take off. Air speed is what causes lift, not wheel speed. Or at least thats what my brain is telling me despite not being an engineer
Posted on 4/10/24 at 6:15 pm to Volvagia
quote:
As written, the plane will actually not take off.
That was my point in the OG thread 15 years ago about this. The way it’s written, if the conveyor truly does “match the speed of the wheels” then it can’t take off. In reality, that isn’t possible and a plane can very easily take off on a conveyor. My issue was always with how it was written.
The Mythbusters episode on this was pretty cool the way they did it.
This post was edited on 4/10/24 at 6:42 pm
Posted on 4/10/24 at 6:32 pm to Street Hawk
It's Boeing. We don't know.
Posted on 4/10/24 at 6:41 pm to Scruffy
No. The argument is the friction between the tires and the ground is not enough to stop the thrust from the engines from pulling the plane forward.
Imagine a plane going down a runway with rubber sleds instead of tires. There would be a lot of burning smoke, but the plane would move forward and take off.
Imagine a plane going down a runway with rubber sleds instead of tires. There would be a lot of burning smoke, but the plane would move forward and take off.
Posted on 4/10/24 at 6:44 pm to Scruffy
quote:
If you put a jet engine with wheels on a treadmill, and the engine has a max speed of, say, 800 mph, and the treadmill is moving at the exact same speed in the opposite direction, 800 mph, your stance is that the jet engine would move forward?
The engine would move forward even if the treadmill was spinning 800, 801, or 8100mph.
Posted on 4/10/24 at 7:06 pm to LNCHBOX
quote:
the actual plane. quote:
At least that is how people are reading it.
People are stupid
Ah, the classic “I’m an engineer and that could never happen in real life so I’m not going to actually answer the hypothetical question ill answer what would happen in real life”
But let’s ignore the fact there’s a picture of a 747 and there’s a conveyer belt the size and length of a runway.
Posted on 4/10/24 at 7:18 pm to baldona
Somehow I knew something dumb was coming when I saw you were the most recent reply.
Posted on 4/10/24 at 7:22 pm to baldona
quote:
But let’s ignore the fact there’s a picture of a 747 and there’s a conveyer belt the size and length of a runway.
Yeah, the point of this hypothetical is to demonstrate that engines don't cause a plane to fly up into the air, but rather the aerodynamical properties and shape of the wings themselves do that when they are pushed (by an engine) or pulled (by a propeller) through distances of airspace.
The treadmill plane doesn't work because the wings remain in the same place rather than cutting through air thus you get no lift.
The reason they de-ice a plane's wings in wintery weather is because the air molecules will "slide" or "shimmer" off an icy surface rather than form a natural lift pocket and in that moment you are riding in a missile, not a plane. See - several famous plane crashes.
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