Plane

[Swango1980]

Well this is new and contradicts "The conveyor belt is programmed to match the speed of the plane's wheels in the opposite direction, perfectly counteracting their rotation."

I don't get why you keep banging on about drive.
If I'm driving my car in 5th gear at 70mph, my speed is 70mph.
If my car is in neutral going down a hill at 70mph, my speed is 70mph.
If I'm on roller skates with a jet pack on my back doing 70mph, my speed is 70mph.
If I'm in a jumbo jet on a conveyor belt that perfectly opposes the speed of my wheels, which are rotating at 70mph, I'm stationary. If my jumbo jet starts moving down the conveyor belt at 70mph then it's wheels are rotating 70mph faster than the conveyor belt is moving and I'm not complying with the fundamental rule of the puzzle.

The paradox exists if one thinks the treadmill is working backwards, and you are thinking of the current speed of wheels and belt match. That is perfectly fine if it is a car. But not a plane that generates thrust, a force not exerted through the ground but through the air. This is how I was initially picturing it, as most others were, and it is impossible. A pilot tries to take off, they will take off. The wheels will always be faster than belt. Because plane speeds them up as it moves forward, belt reacts my matching their speed backwards. But that speeds wheels up even more, coupled with the increased speed of plane. So, belt can never catch up. A programmer could create the program, but treadmill would just continually speed up exponentially.

But, if the programmer designed it to go forwards, the OP works. The plane starts to move forwards to give the wheels speed. Where the wheels contact belt, the movement is backwards. Treadmill reacts my going the same speed as wheels but forwards. This counters their rotation, meaning they no longer rotate. Plane will keep accelerating and adding speed to wheels. But belt continually reacts by matching the increased speed fro wheels in opposite direction. So, the belt effectively is designed to match the speed the wheels want to go at, but in opposite direction. Their rotation is countered and just as plane takes off at 180mph the belt will be going 180mph in same direction as plane.

 

[Deleted member 35927]

Well this is new and contradicts "The conveyor belt is programmed to match the speed of the plane's wheels in the opposite direction, perfectly counteracting their rotation."

I don't get why you keep banging on about drive.
If I'm driving my car in 5th gear at 70mph, my speed is 70mph.
If my car is in neutral going down a hill at 70mph, my speed is 70mph.
If I'm on roller skates with a jet pack on my back doing 70mph, my speed is 70mph.
If I'm in a jumbo jet on a conveyor belt that perfectly opposes the speed of my wheels, which are rotating at 70mph, I'm stationary. If my jumbo jet starts moving down the conveyor belt at 70mph then it's wheels are rotating 70mph faster than the conveyor belt is moving and I'm not complying with the fundamental rule of the puzzle.

Because time and time again you make the error of assuming the plane and car behave in a similar fashion.
You understood how it worked once, nothing has changed.

You cannot ignore the lews of motion , where is the force required to slow the planes acceleration coming from?

It's not the belt, thats just acting against the wheels and they are just free spinning so can't act against the thrust .
So where is that thrust going?

 

[Deleted member 35927]

Paradox may, or may not, be the correct word.

Yes the plane will take off. The thrust generated means that will happen. But in doing so, the wheels cannot be in perfect sync with the conveyor. But if the wheels are in perfect sync with the conveyor, it cant move forward. So the conditions of the problem can't be met.

Perfect synch with the runway, this is new.

 

[Voyager EMH]

If the conveyor moves forward.
First of all it is not moving at all because the plane's wheels are not moving - the conveyor is matching the zero speed.
The plane's engines engage to overcome friction and the plane starts to move forwards.
The plane fails to move forwards, because the conveyor instantaneously moves to counteract the plane's movement.
The plane's engines increase power, but again the conveyor increases its speed.
The plane maintains its position ON THE CONVEYOR, but it is being carried forwards on the conveyor.
Once the conveyor reaches 185mph the plane takes off.
The plane has used, just about, the same amount of fuel as in a normal takeoff on a normal runway and to observer the plane has had a normal takeoff unaffected by the conveyor.
The conveyor obeyed its programming.

Unless I'm wrong.

 

[Deleted member 35927]

If the conveyor moves forward.
First of all it is not moving at all because the plane's wheels are not moving - the conveyor is matching the zero speed.
The plane's engines engage to overcome friction and the plane starts to move forwards.
The plane fails to move forwards, because the conveyor instantaneously moves to counteract the plane's movement.
The plane's engines increase power, but again the conveyor increases its speed.
The plane maintains its position ON THE CONVEYOR, but it is being carried forwards on the conveyor.
Once the conveyor reaches 185mph the plane takes off.
The plane has used, just about, the same amount of fuel as in a normal takeoff on a normal runway and to observer the plane has had a normal takeoff unaffected by the conveyor.
The conveyor obeyed its programming.

Unless I'm wrong.

I think that's a very fair assessment.

 

[backwoodsman]

I use '... in perfect sync ...' as shorthand for '... programmed to match the speed of the plane's wheels in the opposite direction, perfectly countacting their rotation...' Which is what the OP said.

If the conveyor belt is '... programmed to match the speed of the plane's wheels in the opposite direction, perfectly counteracting their rotation...' then the wheels (ergo the plane) must stay at a fixed point on the conveyor. They/it cannot be moving forward, or backward, in relation to the conveyor. To move forward, or backward, the wheels must be moving at a different speed to the conveyor. But the considerable thrust of the engine means frictional/gravitational/inertial forces are overcome - so the plane must move forward. But if is moving forward, then the wheels cannot be '... programmed to match the speed of the plane's wheels in the opposite direction, perfectly countacting their rotation...'.

But they are matched, but they can't be, but they are, but they can't be - ad infinitum.

Dichotomy is probably a better word than paradox

I knew I shouldnt have got involved, so that's me out ...

 

[Voyager EMH]

Any forward motion would require the roller skate wheels to be faster than the conveyor, which is verboten.
Stationary wheels become the pivot, force of the jet pack becomes torque around the pivot. Face plant.

You have to go right back to post#408 to see that we were discussing the difference between a sprinter at 10 metres per second striding onto a conveyor at a constant speed and the difference this would be to a person on rollerskates powered by a jet pack mounting the same conveyor.
We were not discussing the scenario of the increasing speed conveyor.

 

[Swango1980]

If the conveyor moves forward.
First of all it is not moving at all because the plane's wheels are not moving - the conveyor is matching the zero speed.
The plane's engines engage to overcome friction and the plane starts to move forwards.
The plane fails to move forwards, because the conveyor instantaneously moves to counteract the plane's movement.
The plane's engines increase power, but again the conveyor increases its speed.
The plane maintains its position ON THE CONVEYOR, but it is being carried forwards on the conveyor.
Once the conveyor reaches 185mph the plane takes off.
The plane has used, just about, the same amount of fuel as in a normal takeoff on a normal runway and to observer the plane has had a normal takeoff unaffected by the conveyor.
The conveyor obeyed its programming.

Unless I'm wrong.

That is fair. But just a minor point. The plane isn't actually being carried forwards BY the belt, but it would appear that way to the observer. The engines are causing it to move as normal, and the belt is responding to this by matching its speed, due to the inputs it gets to counteract the wheels rotation

 

[Voyager EMH]

That is fair. But just a minor point. The plane isn't actually being carried forwards BY the belt, but it would appear that way to the observer. The engines are causing it to move as normal, and the belt is responding to this by matching its speed, due to the inputs it gets to counteract the wheels rotation

Ah, my mistake.

Should I go back and edit BY to ON ?



(EDIT: I went back to check and I could not find where I had typed "carried forward by the conveyor")

 

[RichA]

If the conveyor moves forward.
First of all it is not moving at all because the plane's wheels are not moving - the conveyor is matching the zero speed.
The plane's engines engage to overcome friction and the plane starts to move forwards.
The plane fails to move forwards, because the conveyor instantaneously moves to counteract the plane's movement.
The plane's engines increase power, but again the conveyor increases its speed.
The plane maintains its position ON THE CONVEYOR, but it is being carried forwards on the conveyor.
Once the conveyor reaches 185mph the plane takes off.
The plane has used, just about, the same amount of fuel as in a normal takeoff on a normal runway and to observer the plane has had a normal takeoff unaffected by the conveyor.
The conveyor obeyed its programming.

Unless I'm wrong.

If the plane's position on the conveyor is static then the wheels aren't rotating and the conveyor should be motionless.

 

[Voyager EMH]

If the plane's position on the conveyor is static then the wheels aren't rotating and the conveyor should be motionless.

No.

The power of the engines is attempting to move the plane, but this is instantaneously negated by an increase in speed of the conveyor. The conveyor obeying its programming.

If the conveyor failed its programming then the wheels would move, then plane would move forwards and take off as normal.

 

[Voyager EMH]

Going back to post#408 again, this is one of the finest statements on this thread,

"That is exactly the same as a plane travelling at 180mph landing on a conveyor travelling at 180mph in the opposite direction, the plane will travel at 180mph in relation to the conveyor but will not be moving in relation to the fixed tarmac."

Trump has just read this and is getting Musk to build aircraft carriers with conveyor belts to land jumbo jets on.

 

[GreiginFife]

Going back to post#408 again, this is one of the finest statements on this thread,

"That is exactly the same as a plane travelling at 180mph landing on a conveyor travelling at 180mph in the opposite direction, the plane will travel at 180mph in relation to the conveyor but will not be moving in relation to the fixed tarmac."

Trump has just read this and is getting Musk to build aircraft carriers with conveyor belts to land jumbo jets on.

Bit like a rolling road. When power testing my car it was "travelling" at 155mph on the rolling road without actually moving anywhere. But the power to move it at 155mph was still being generated.

Was cacking my pants that the rollers didn't fail!

 

[Voyager EMH]

Bit like a rolling road. When power testing my car it was "travelling" at 155mph on the rolling road without actually moving anywhere. But the power to move it at 155mph was still being generated.

Was cacking my pants that the rollers didn't fail!

What was powering the rolling road to go at 155mph in the opposite direction to your car?

 

[Swango1980]

Ah, my mistake.

Should I go back and edit BY to ON ?



(EDIT: I went back to check and I could not find where I had typed "carried forward by the conveyor")

Apologies, was on my phone so I couldn't highlight (easily) the bit I was responding to by bolding it. It was the line: "but it is being carried forwards on the conveyor" as that read to me like the belt was carrying the plane. Whereas in reality the engine is propelling the plane as normal, and the belt is reacting. In effect, it is really the plane that is carrying / driving the belt forwards

 

[GreiginFife]

What was powering the rolling road to go at 155mph in the opposite direction to your car?

The engine.

 

[Voyager EMH]

The engine.

Do you mean that your car's engine was powering the rolling road, or did the rolling road have an engine of its own?

 

[GreiginFife]

Do you mean that your car's engine was powering the rolling road, or did the rolling road have an engine of its own?

Car. Rolling road only had an emergency brake.

 

[Deleted member 35927]

Bit like a rolling road. When power testing my car it was "travelling" at 155mph on the rolling road without actually moving anywhere. But the power to move it at 155mph was still being generated.

Was cacking my pants that the rollers didn't fail!

This is where people (not you personally I'm sure ) get confused , as you say strapping your car to a Dyno and driving will cause the wheels to turn and the Dyno rollers to spin . Strap a plane to the Dyno and hit the throttle and you'd get a lot of noise and little else.

 

[GreiginFife]

This is where people (not you personally I'm sure ) get confused , as you say strapping your car to a Dyno and driving will cause the wheels to turn and the Dyno rollers to spin . Strap a plane to the Dyno and hit the throttle and you'd get a lot of noise and little else.

No, I know as the plane wheels are not driven. Was merely trying to give an example of moving without moving.

Obviously badly.

I’ll leave the experts to it.