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Started By
Message
re: Can this 747 take off?
Posted on 4/11/24 at 1:03 pm to tigerfoot
Posted on 4/11/24 at 1:03 pm to tigerfoot
quote:
Again, irrelevant, this scenario has wheels and tires that are exactly matched to the treadmill or belt.
You are starting to learn why the question is broken.
1) the airplane will always thrust forward on a treadmill. The airplane thrust is against the atmosphere. That is why the wheels are free moving. They are not needed for torque or power or anything.
Thus
2) the wheels will always be rotating faster than the treadmill.
Thus
3) the question is broken for a plane and treadmill.
If you want to adhere to the rules of the question... lock the brakes on the wheels (so they are no longer free. But the wheels cannot move at all either).
In this scenario...
1) the wheels will not move. Thus the treadmill does not move.
2) 240,000 pounds of thrust wins and despite the wheels being locked up on the ground, the plane moves forward and takes off.
Under both scenarios (the broken one where the wheels move faster than the treadmill because of physics and the scenario where the wheels and treadmill do not move at all), the plane takes off.
1
Posted on 4/11/24 at 1:03 pm to LNCHBOX
At this point I’m convinced a sizable number of people think when planes land, the engines are used to generate power to drive the wheels.
Posted on 4/11/24 at 1:05 pm to Volvagia
quote:Of course. But in this scenario, that was not mentioned.
If there is a wind that matches take off velocity, a plane can take off with zero ground velocity, because it’s built to run with respect to air.
quote:Are you sure this says what you think it says
For the Belt-ivan logic to hold, and have speeds have equal relevance between frames of reference, it would mean a person couldn’t walk into a 20+mph wind ever. That is past athlete sprinting speed. According to yall, it doesn’t matter that you walk by pressing against the ground, the wind should counter it!
Posted on 4/11/24 at 1:07 pm to meansonny
quote:All great, and alot of words. But not part of how the question is posed.
In this scenario...
1) the wheels will not move. Thus the treadmill does not move.
2) 240,000 pounds of thrust wins and despite the wheels being locked up on the ground, the plane moves forward and takes off.
Under both scenarios (the broken one where the wheels move faster than the treadmill because of physics and the scenario where the wheels and treadmill do not move at all), the plane takes off.
BETA Page
Posted on 4/11/24 at 1:08 pm to tigerfoot
quote:
Of course. But in this scenario, that was not mentioned.
Did you need them to explicitly tell you that the engines will be used to attempt to take off? Again, where can I send your dunce cap?
Posted on 4/11/24 at 1:08 pm to Volvagia
quote:
At this point I’m convinced a sizable number of people think when planes land, the engines are used to generate power to drive the wheels.
Ironically an electric system was tried with ETGS for taxiing.
This post was edited on 4/11/24 at 1:10 pm
Posted on 4/11/24 at 1:10 pm to LNCHBOX
quote:
Another poster deflecting when they can't argue the logic
Interesting. I notice you haven't answered how the plane can take off with no air moving across the wings, or no lift.
Posted on 4/11/24 at 1:11 pm to TD422
quote:
Interesting. I notice you haven't answered how the plane can take off with no air moving across the wings, or no lift.
I answered it by telling you why the plane would be moving
Posted on 4/11/24 at 1:14 pm to TD422
quote:
I notice you haven't answered how the plane can take off with no air moving across the wings, or no lift.
Absolutely no one claimed they did.
Again, this was physically tried!
The conveyor was set to take off air speed.
There was no wind.
The plane took off with no additional throttle, and no additional runway.
If it had an effect, there should have at least been a significant delay in take off time.
And at NO point did the plane go backwards when the belt backward exceeded the current plane’s forward ground velocity
Posted on 4/11/24 at 1:17 pm to LNCHBOX
How is the plane moving FORWARD if the belt speed matches the wheel speed?
Posted on 4/11/24 at 1:18 pm to TD422
quote:
How is the plane moving FORWARD if the belt speed matches the wheel speed?
Already answered.
Posted on 4/11/24 at 1:19 pm to Volvagia
Are you talking about the Mythbusters video?
Posted on 4/11/24 at 1:20 pm to TD422
quote:
How is the plane moving FORWARD if the belt speed matches the wheel speed?
Because the wheels aren’t what pushes the plane forward.
Do you think a rocket on sleds would stay put on a conveyor belt as well?
Posted on 4/11/24 at 1:21 pm to Volvagia
The problem here is nobody is on the same page if the conveyor belt is moving the plane forward or is the conveyor belt keeping the plane in a fixed relative location. If that is answered properly the answers are yes and no respectively.
Posted on 4/11/24 at 1:24 pm to Volvagia
See, this goes back to my earlier post about 12 different discussions.
The question I believe you're answering is: "If appropriate thrust is applied, can this plane take off?
OF COURSE! But that variable wasn't included in the OP / original question. Furthermore, if the wheel speed of the plane matches the belt, it would have to be presumed no thrust is being applied. Therefore, the plane is stationary relative to the ground, and no air is flowing over the wings....
The question I believe you're answering is: "If appropriate thrust is applied, can this plane take off?
OF COURSE! But that variable wasn't included in the OP / original question. Furthermore, if the wheel speed of the plane matches the belt, it would have to be presumed no thrust is being applied. Therefore, the plane is stationary relative to the ground, and no air is flowing over the wings....
Posted on 4/11/24 at 1:25 pm to TD422
quote:
But that variable wasn't included in the OP / original question.
How was thrust not part of the question? How the frick else is the plane taking off?
Posted on 4/11/24 at 1:28 pm to sidewalkside
quote:
The problem here is nobody is on the same page if the conveyor belt is moving the plane forward or is the conveyor belt keeping the plane in a fixed relative location. If that is answered properly the answers are yes and no respectively.
No it isn’t.
Literally the only ways a conveyor belt can stop the plane from taking off are:
(1) by forcing the wheels to spin so fast that they fail entirely
(2)assuming magical indestructible bearings in the wheels allowing the conveyor belt to move at an absolutely absurd speed (like multiples of speed of sound) such that the friction within the wheels cancels engine thrust.
Assuming frictionless wheels, there are no speeds the belt can move at that will impede, much less stop, the plane from taking off.
Posted on 4/11/24 at 1:29 pm to TD422
quote:
OF COURSE! But that variable wasn't included in the OP / original question. Furthermore, if the wheel speed of the plane matches the belt, it would have to be presumed no thrust is being applied. Therefore, the plane is stationary relative to the ground, and no air is flowing over the wings....
You do realize the only time this is true is when both the belt and the wheel are stationary
Right?
Because if there is no thrust being applied the wheel isn’t moving.
This post was edited on 4/11/24 at 1:32 pm
Posted on 4/11/24 at 1:31 pm to LNCHBOX
What do you do for a living, Chief?
In my world, details matter. If I read something that isn't there, I'd be out of business by losing job after job. And by not reading something that IS there...well, that'll cost me as well.
You made an assumption that was not introduced into the parameters of the question.
In my world, details matter. If I read something that isn't there, I'd be out of business by losing job after job. And by not reading something that IS there...well, that'll cost me as well.
You made an assumption that was not introduced into the parameters of the question.
Posted on 4/11/24 at 1:31 pm to tigerfoot
quote:
All great, and alot of words. But not part of how the question is posed.
The question is broken.
The only way to design a treadmill where the wheels and treadmill go the same speed is to lock the wheels which locks the treadmill.
And I addressed that the 240,000 pounds of thrust from a 747 would achieve flight.
It is impossible to design a treadmill that goes faster than a freewheel.
Why? Because a free wheel is designed to move forward or backwards with external forces (forces which have no relevance to the treadmill).
The only way to guarantee the same speed of the wheels and treadmill is to keep the speed of the wheels and treadmill at 0.
Outside of 0, any force applied to the freewheel object will create faster wheel rotation (rolling it forward on the treadmill) or slower wheel rotation (rolling it backwards on the treadmill).
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