physics puzzle no.2
- Thread starter noseall
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I can't believe there's ANOTHER thread about this, I've just posted on the last one ... Has everyone gone totally mad 
I think Doitall must be going for the wind up trophy fellas as he's posting total nonsense and you are all falling for it as far as I can see.
I'm not going to reply any more to this one as it's pointless so I'll just add my post from the last and leave you all to it ...
An aircraft needs airspeed to take off not groundspeed and there can be anything from a 0:1 - 1:1 - 1:0 relationship between them. If you assume an aircraft's T/O speed is 30 knots ... with no head or tail winds airspeed = groundspeed and T/O will occur at 30 knots groundspeed, 30 knots tailwind and T/O will occur at 60 knots groundspeed and ... Wait for it ... 30 knots headwind T/O will occur at zero groundspeed ... Irrespective of what the runway or wheels are doing.
The only purpose wheels serve to an aircraft is supporting it whilst it is on the ground and they play no part whatsoever in it getting airborne ... Someone has already pointed out both on this thread (I think) and certainly the previous that the aircraft will take off normally but the wheels will be spun to infinity based on the OP's question ... The wheels may not survive but the aircraft will take off quite normally.
You need to understand that the thrust of the engines moves the airframe relative to the airflow around it NOT with respect to the ground.
This is a classic connundrum which has been used to provide amusement to both trainee engineers and pilots ever since I learnt to fly in 1983.
The aircraft will takeoff and the pilots won't see any difference to a normal runway ... Other than losing their wheels of course, but that wasn't the OP's question
MW
I think Doitall must be going for the wind up trophy fellas as he's posting total nonsense and you are all falling for it as far as I can see.
I'm not going to reply any more to this one as it's pointless so I'll just add my post from the last and leave you all to it ...
Nope, quite wrong.
An aircraft needs airspeed to take off not groundspeed and there can be anything from a 0:1 - 1:1 - 1:0 relationship between them. If you assume an aircraft's T/O speed is 30 knots ... with no head or tail winds airspeed = groundspeed and T/O will occur at 30 knots groundspeed, 30 knots tailwind and T/O will occur at 60 knots groundspeed and ... Wait for it ... 30 knots headwind T/O will occur at zero groundspeed ... Irrespective of what the runway or wheels are doing.
The only purpose wheels serve to an aircraft is supporting it whilst it is on the ground and they play no part whatsoever in it getting airborne ... Someone has already pointed out both on this thread (I think) and certainly the previous that the aircraft will take off normally but the wheels will be spun to infinity based on the OP's question ... The wheels may not survive but the aircraft will take off quite normally.
You need to understand that the thrust of the engines moves the airframe relative to the airflow around it NOT with respect to the ground.
This is a classic connundrum which has been used to provide amusement to both trainee engineers and pilots ever since I learnt to fly in 1983.
The aircraft will takeoff and the pilots won't see any difference to a normal runway ... Other than losing their wheels of course, but that wasn't the OP's question
MW
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Was this when you went short-sighted?
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noseall, yes your object will move forwards, quite easily.
As regards the aircraft, please consider the following...
We have a plane on the conveyor, the plane is not moving, the wheels are not moving, the conveyor is not moving, bear with me.
Now those people who believe the plane can not take off, tell us that the plane can be doing 100mph, whilst the conveyor below travels in the opposite direction at 100 mph, so the plane is not moving.
If the plane is not moving, the wheels will not turn, therefore the conveyor can not move.
Remember the conveyor REACTS to wheel MOVEMENT not vice verca.
For the conveyor to react to wheel movement, the plane must be moving FORWARDS.
The conveyor just speeds up to match the wheel speed as the plane speeds up, and then takes off.
Remember this is a theoretical question, and I have ignored the impossibility of constructing such a device, and making wheels which could stand the strain.
As regards the aircraft, please consider the following...
We have a plane on the conveyor, the plane is not moving, the wheels are not moving, the conveyor is not moving, bear with me.
Now those people who believe the plane can not take off, tell us that the plane can be doing 100mph, whilst the conveyor below travels in the opposite direction at 100 mph, so the plane is not moving.
If the plane is not moving, the wheels will not turn, therefore the conveyor can not move.
Remember the conveyor REACTS to wheel MOVEMENT not vice verca.
For the conveyor to react to wheel movement, the plane must be moving FORWARDS.
The conveyor just speeds up to match the wheel speed as the plane speeds up, and then takes off.
Remember this is a theoretical question, and I have ignored the impossibility of constructing such a device, and making wheels which could stand the strain.
as far as force goes, whats the difference between a winch and a jet engine, only that the jet engine is more powerful?
Their is no difference, if you read my post, I am firmly in the camp of, It will take off
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So the conveyor speed must lag behind the wheel speed as the plane moves forward.
If the plane continues to move forward, the wheel speed is then going to be massively accelerated by the conveyor.
It's a theoretical question, but the plane still has to be constrained by the laws of physics. If you overspeed the wheels by a significant margin the tyres will be destroyed, then the wheels. The conveyor could be engineered to exceed this speed.
With regards to the OP - the plane takes off.
As numerous people have pointed out the engines work with the air around the plane, not the ground. If they worked with the ground we wouldn't be going on holiday in jet aircraft as they would start falling the minute they left the ground
Now vis a vis the hypothetical conveyor belt that exactly matches the rotation of the wheels - the plane still takes off, the conveyor doesn't move...nobody specified a particular plane so I choose a Harrier - goes straight up with no forward movement required
As numerous people have pointed out the engines work with the air around the plane, not the ground. If they worked with the ground we wouldn't be going on holiday in jet aircraft as they would start falling the minute they left the ground
Now vis a vis the hypothetical conveyor belt that exactly matches the rotation of the wheels - the plane still takes off, the conveyor doesn't move...nobody specified a particular plane so I choose a Harrier - goes straight up with no forward movement required
You can't because this isn't your thread
we have a mystery object on the belt being winched along
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