Plane

[Whereditgo]

I’ve quite enjoyed reading the discussions.

One thing I’m now not sure about though is which direction people are imagining the conveyor to be travelling in.

My take on it:

If the part of the conveyor in contact with the aircrafts wheels is travelling in the same direction that the aircraft would move to gain flight, then as the thrust increases and the aircraft is pushed forwards, the wheels would attempt to rotate but the conveyor would instantaneously (not really practicable) start to move thus “perfectly counteracting their rotation”. The wheel would not rotate even as the aircraft continued to accelerate until the take-off speed was achieved.

If the part of the conveyor in contact with the aircrafts wheels is travelling in the opposite direction to the aircrafts thrust, then both the wheels and the conveyor would continue to accelerate until such time as the wheels lose contact with the conveyor. The wheels are not driven by anything other than the contact with the conveyor, they are freewheeling, whereas the aircraft has a force acting against it and no equal and opposite force to prevent it moving relative to the ground. Imagine standing on a treadmill wearing roller skates, hold onto the hand rails for balance and have someone accelerate the treadmill, at the same time pull backwards with your arms. You would move forwards relative to the ground.

 

[Deleted member 36735]

Imagine standing on a treadmill wearing roller skates, hold onto the hand rails for balance and have someone accelerate the treadmill, at the same time pull backwards with your arms. You would move forwards relative to the ground.

I agree with most of what you wrote, but this is a very small but vital piece of the puzzle which isn't as you've written.

The puzzle doesn't say that the conveyor starts first and something is already stopping the person on roller skates (or the plane) moving backwards (in this case holding onto the handrails).

In the case of roller skates, if someone was standing on a treadmill on roller skates and the treadmill started slowly moving backwards, there might be a small amount of free-wheeling but there would be plenty enough friction for the person to move backwards with the movement of the treadmill, they can't just stay in a fixed position without some force propelling them forwards.

The puzzle states that the treadmill always equals and counteracts the speed of the wheels. So once the person is stationary (although the wheels are rolling forward in relation to the treadmill) if the person grabbed the handrails and pulled themselves forward, the rule states that the treadmill accelerates to counter the faster rolling of the wheels, hence they can't move forward.

 

[Voyager EMH]

The puzzle states that the treadmill always equals and counteracts the speed of the wheels. So once the person is stationary (although the wheels are rolling forward in relation to the treadmill) if the person grabbed the handrails and pulled themselves forward, the rule states that the treadmill accelerates to counter the faster rolling of the wheels, hence they can't move forward.

Can't happen that way.
The thread is all about why that can't happen that way.

Wheels of plane turning in an equal and opposite way to the conveyor - the plane takes of as normal.

 

[Deleted member 35927]

I agree with most of what you wrote, but this is a very small but vital piece of the puzzle which isn't as you've written.

The puzzle doesn't say that the conveyor starts first and something is already stopping the person on roller skates (or the plane) moving backwards (in this case holding onto the handrails).

In the case of roller skates, if someone was standing on a treadmill on roller skates and the treadmill started slowly moving backwards, there might be a small amount of free-wheeling but there would be plenty enough friction for the person to move backwards with the movement of the treadmill, they can't just stay in a fixed position without some force propelling them forwards.

The puzzle states that the treadmill always equals and counteracts the speed of the wheels. So once the person is stationary (although the wheels are rolling forward in relation to the treadmill) if the person grabbed the handrails and pulled themselves forward, the rule states that the treadmill accelerates to counter the faster rolling of the wheels, hence they can't move forward.

I can't believe you're still sticking to this.
What is countering the massive force of the jets ?
The conveyor and wheels can't, which leaves only magic ....
And as much as I like the Witcher , that's just make believe.

 

[Swango1980]

I agree with most of what you wrote, but this is a very small but vital piece of the puzzle which isn't as you've written.

The puzzle doesn't say that the conveyor starts first and something is already stopping the person on roller skates (or the plane) moving backwards (in this case holding onto the handrails).

In the case of roller skates, if someone was standing on a treadmill on roller skates and the treadmill started slowly moving backwards, there might be a small amount of free-wheeling but there would be plenty enough friction for the person to move backwards with the movement of the treadmill, they can't just stay in a fixed position without some force propelling them forwards.

The puzzle states that the treadmill always equals and counteracts the speed of the wheels. So once the person is stationary (although the wheels are rolling forward in relation to the treadmill) if the person grabbed the handrails and pulled themselves forward, the rule states that the treadmill accelerates to counter the faster rolling of the wheels, hence they can't move forward.

So, if you were that person on roller skates on a treadmill, and it was designed to speed up backwards as the wheels sped up forwards, then you would find it impossible to ever drag yourself forwards? You pull forwards with all your strength on the treadmill, and you just can't so it?

 

[RichA]

The giant fan would have to maintain its position in front of the plane.
If it and the plane are both stationary, no conveyor, lift is created, but where does the plane go?
Does the fan have to takeoff as well to keep level with the plane and keep the plane in the air?

A plane with a fan in fixed in front of it. There's an idea. I've made some preliminary sketches and think it's worth applying for a patent...

 

[Deleted member 36735]

So, if you were that person on roller skates on a treadmill, and it was designed to speed up backwards as the wheels sped up forwards, then you would find it impossible to ever drag yourself forwards? You pull forwards with all your strength on the treadmill, and you just can't so it?

It's all about the rule of the puzzle.

The treadmill is designed to counteract the movement of the wheels, so they would have to skid or slide or the person would have to lift them off the treadmill and run or do that fast skating action in order to move forwards in relation to a fixed point.
I'm illustrating no movement of the legs in line with what you guys have said all along, ie nothing is driving the wheels, they are just passive.
So the example I'm using is someone just standing on the treadmill, we have to follow the main rule so if the arms exert a force and pull the body and legs forward, the treadmill is programmed to counteract that acceleration.

I'm deliberately not mentioning a plane with engines, lift etc, merely a simple example of a pair of skates on a treadmill.

 

[Whereditgo]

It's all about the rule of the puzzle.

The treadmill is designed to counteract the movement of the wheels, so they would have to skid or slide or the person would have to lift them off the treadmill and run or do that fast skating action in order to move forwards in relation to a fixed point.
I'm illustrating no movement of the legs in line with what you guys have said all along, ie nothing is driving the wheels, they are just passive.
So the example I'm using is someone just standing on the treadmill, we have to follow the main rule so if the arms exert a force and pull the body and legs forward, the treadmill is programmed to counteract that acceleration.

I'm deliberately not mentioning a plane with engines, lift etc, merely a simple example of a pair of skates on a treadmill.

And the treadmill (conveyor) and wheels would both continue to accelerate (probably/possibly? at the same rate of acceleration as the force imparted on the skater (aircraft)), the conveyor in response to the control strategy and the wheels in reaction to the treadmill (conveyor), however both in response to the force that was moving the skater (aircraft) forwards.

 

[RichA]

It's all about the rule of the puzzle.

The treadmill is designed to counteract the movement of the wheels, so they would have to skid or slide or the person would have to lift them off the treadmill and run or do that fast skating action in order to move forwards in relation to a fixed point.
I'm illustrating no movement of the legs in line with what you guys have said all along, ie nothing is driving the wheels, they are just passive.
So the example I'm using is someone just standing on the treadmill, we have to follow the main rule so if the arms exert a force and pull the body and legs forward, the treadmill is programmed to counteract that acceleration.

I'm deliberately not mentioning a plane with engines, lift etc, merely a simple example of a pair of skates on a treadmill.

The problem is that whichever side of the argment we are on, we are forced to make up our own rules because the puzzle only provides 1 - speed matching of tyres and conveyor.
Due to the overall unfeasibility of the scenario, I saw it as a pure mechanical puzzle where there was always perfect traction between wheels and conveyor belt, hence my explanation that the plane tips forward.

The other side of the argument is that there can't be perfect traction between reinforced rubber tyres and the conveyor belt when the wheels have 250,000 bhp pushing the vehicle they're attached to. It makes sense, but I saw this as cheating the puzzle.

Then even if the conveyor is built and a spare 747 is acquired, you still need to find a pilot that trusts that the tyres won't explode while the 300 ton plane is basically wheelspinning its way to takeoff speed. This is where somebody adds a new rule that the contact between wheels and conveyor belt is frictionless.

 

[Deleted member 36735]

And the treadmill (conveyor) and wheels would both continue to accelerate in response to the force that was moving the skater (aircraft) forwards.

Yes exactly, that is the specific part of the puzzle. So if the treadmill always matches the speed of a wheel on it, the wheel can't move in relation to fixed points.

Earlier in the thread I used an example of a pushbike.

Imagine if I placed a free-wheeling pushbike on a treadmill. If the treadmill is moving backwards at 10mph, I need to hold the saddle and exert a force on the bike equivalent to pushing it forward at 10mph in relation to the treadmill for it to be stationary. Outside of the treadmill, that force has zero forward speed because I'm just holding it steady.

If I then exerted a force to send it forward at 20mph in relation to the treadmill, it would then move at 10mph forward in relation to normal fixed points if the treadmill stayed moving backwards at 10mph.

BUT the rule of the puzzle is that whatever the speed of the wheels, the treadmill will always match and counteract, this is the bit keeps being overlooked. So whatever extra force I apply to the bike, however fast I try and push it forward, the main rule of this silly puzzle says that the treadmill always counteracts that, so I can't push the bike forward in relation to fixed points if the wheels are rolling over the treadmill.

 

[Voyager EMH]

The plane is stationary on a stationary conveyor.

Plane engages power.
Plane is at the point of overcoming friction - at the point where the wheels should start to move in the next moment.
They conveyor can not yet act.
Planes wheels start to move.
Conveyor engages.
But the planes wheels started first. The conveyor is programmed to "counteract". It can't counteract until something has happened for it to counteract to.
Plane's wheels have already moved and the conveyor can not stop them from moving no matter how much it speeds up.
Plane takes off as normal, because friction was overcome just like on a normal takeoff on a normal runway.

 

[Deleted member 35927]

Yes exactly, that is the specific part of the puzzle. So if the treadmill always matches the speed of a wheel on it, the wheel can't move in relation to fixed points.

Earlier in the thread I used an example of a pushbike.

Imagine if I placed a free-wheeling pushbike on a treadmill. If the treadmill is moving backwards at 10mph, I need to hold the saddle and exert a force on the bike equivalent to pushing it forward at 10mph in relation to the treadmill for it to be stationary. Outside of the treadmill, that force has zero forward speed because I'm just holding it steady.

If I then exerted a force to send it forward at 20mph in relation to the treadmill, it would then move at 10mph forward in relation to normal fixed points if the treadmill stayed moving backwards at 10mph.

BUT the rule of the puzzle is that whatever the speed of the wheels, the treadmill will always match and counteract, this is the bit keeps being overlooked. So whatever extra force I apply to the bike, however fast I try and push it forward, the main rule of this silly puzzle says that the treadmill always counteracts that, so I can't push the bike forward in relation to fixed points if the wheels are rolling over the treadmill.

I'm staggered how you keep making the same mistake over and over.
The plane wheels cannot move unless the plane is moving they have no drive.
It's not a car or a jogger or bike
The only rules you need are the laws of motion.
Explain to me how the freewheeling wheels and belt are offering an opposing force against the 2400000 lbs of thrust.
Not some mumbo jumbo that needs magic , actual detail, numbers.

 

[Swango1980]

Yes exactly, that is the specific part of the puzzle. So if the treadmill always matches the speed of a wheel on it, the wheel can't move in relation to fixed points.

Earlier in the thread I used an example of a pushbike.

Imagine if I placed a free-wheeling pushbike on a treadmill. If the treadmill is moving backwards at 10mph, I need to hold the saddle and exert a force on the bike equivalent to pushing it forward at 10mph in relation to the treadmill for it to be stationary. Outside of the treadmill, that force has zero forward speed because I'm just holding it steady.

If I then exerted a force to send it forward at 20mph in relation to the treadmill, it would then move at 10mph forward in relation to normal fixed points if the treadmill stayed moving backwards at 10mph.

BUT the rule of the puzzle is that whatever the speed of the wheels, the treadmill will always match and counteract, this is the bit keeps being overlooked. So whatever extra force I apply to the bike, however fast I try and push it forward, the main rule of this silly puzzle says that the treadmill always counteracts that, so I can't push the bike forward in relation to fixed points if the wheels are rolling over the treadmill.

This makes no sense at all

If a pushbike was on a treadmill, and the treadmill was moving backwards at 50mph, I can guarantee you that I would be able to hold the bike in position. If that treadmill was switched off, there is absolutely no way that the force I was applying to the bike would be capable of pushing it 50mph down the road.

 

[Deleted member 36735]

The plane is stationary on a stationary conveyor.

Plane engages power.
Plane is at the point of overcoming friction - at the point where the wheels should start to move in the next moment.
They conveyor can not yet act.
Planes wheels start to move.
Conveyor engages.
But the planes wheels started first. The conveyor is programmed to "counteract". It can't counteract until something has happened for it to counteract to.
Plane's wheels have already moved and the conveyor can not stop them from moving no matter how much it speeds up.
Plane takes off as normal, because friction was overcome just like on a normal takeoff on a normal runway.

No you're cheating. You're allowing the wheels to move which against the rule.

Whether you think the conveyor travels against the direction of the plane or with the direction of the plane (which I agree is open to interpretation), the conveyor does not allow the wheels to roll.

It's not about a normal plane's movement, it's about the exact wording of the puzzle.

 

[Swango1980]

It's all about the rule of the puzzle.

The treadmill is designed to counteract the movement of the wheels, so they would have to skid or slide or the person would have to lift them off the treadmill and run or do that fast skating action in order to move forwards in relation to a fixed point.
I'm illustrating no movement of the legs in line with what you guys have said all along, ie nothing is driving the wheels, they are just passive.
So the example I'm using is someone just standing on the treadmill, we have to follow the main rule so if the arms exert a force and pull the body and legs forward, the treadmill is programmed to counteract that acceleration.

I'm deliberately not mentioning a plane with engines, lift etc, merely a simple example of a pair of skates on a treadmill.

The counteracting the rotation of the wheels has been explained. To counteract the speed of the wheels, the conveyor belt actually moved in the direction of the plane at the same speed as the plane.

And if the conveyor belt moved backwards like a treadmill, it does the opposite of counteracting the rotation of the wheels, because that would actually speed up their rotation

 

[Deleted member 36735]

This makes no sense at all

If a pushbike was on a treadmill, and the treadmill was moving backwards at 50mph, I can guarantee you that I would be able to hold the bike in position. If that treadmill was switched off, there is absolutely no way that the force I was applying to the bike would be capable of pushing it 50mph down the road.

OK let me have another beer and think about it

 

[Deleted member 35927]

No you're cheating. You're allowing the wheels to move which against the rule.

Whether you think the conveyor travels against the direction of the plane or with the direction of the plane (which I agree is open to interpretation), the conveyor does not allow the wheels to roll.

It's not about a normal plane's movement, it's about the exact wording of the puzzle.

And as worded it takes off you really are clutching at straws.

 

[Deleted member 36735]

The counteracting the rotation of the wheels has been explained. To counteract the speed of the wheels, the conveyor belt actually moved in the direction of the plane at the same speed as the plane.

And if the conveyor belt moved backwards like a treadmill, it does the opposite of counteracting the rotation of the wheels, because that would actually speed up their rotation

You should stop saying "been explained" because there is more than one interpretation.

It is also clear that the word "counteract" is being understood differently, not necessarily incorrectly by either side. I agree that the treadmill moving forwards "counteracts" according to synonyms, but the treadmill moving backwards most certainly also "counteracts", eg negates/equalises.

 

[Voyager EMH]

No you're cheating. You're allowing the wheels to move which against the rule.

Whether you think the conveyor travels against the direction of the plane or with the direction of the plane (which I agree is open to interpretation), the conveyor does not allow the wheels to roll.

It's not about a normal plane's movement, it's about the exact wording of the puzzle.

The conveyor and the plane start stationary.

There is no event to analyse unless the plane starts its engines in order for the plane to move or attempt to move.

"The conveyor is programmed to" does not include wizardry or time travel.

 

[Swango1980]

You should stop saying "been explained" because there is more than one interpretation.

It is also clear that the word "counteract" is being understood differently, not necessarily incorrectly by either side. I agree that the treadmill moving forwards "counteracts" according to synonyms, but the treadmill moving backwards most certainly also "counteracts", eg negates/equalises.

Moving backwards, I'm not sure what it counteracts. The treadmill could be programmed to go backwards at the same speed as the plane goes forwards. Plane takes off, wheels are moving double fast.

But the OP said counteracting the rotation of the wheels, so I doubt that meant speeding them up. This is the bit I initially paid no real attention to. I jumped to the conclusion the belt would be moving backwards, and regardless of its programming the plane would always take off. But, for everything in the OP to match up, the belt should move forwards with plane. Plane still takes off, but wheels don't rotate.