A plane on a treadmill - physics question

[GB2]

It's not a hovercraft, it's a wheel, with its own laws of physics... forget the plane and everything else, just tell
me one thing: how a wheel can move forward if it's turning at the same speed as the treadmill?

If you forget the plane and everything else and just consider the spinning wheel and the treadmill relationship then no, it would not move if it were spinning at the same rate as the treadmill.

However, the wheel in this airplane/treadmill scenario is attached to the axle of the plane which is pushing it forward, the wheel is not providing it's own forward momentum. The relationship of the wheel to the treadmill is irrelevant and has nothing to do with it's movement. It will be the same case when the plane finally takes off, the wheel will stop spinning but it will still be moving forward.

 

[Andy D]

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View attachment 145981

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This is a post I wrote yesterday & I believe it's irrefutable, just read below and tell me how I'm wrong:

Nothing reacts instantly, but let's assume
the treadmill matches speed almost instantly, like in a millisecond (1/1000 of a second) and the plane moved forward at 5mph:
1st millisecond plane 5mph -treadmill matches.

2nd millisecond plane's tire is forced to 10mph to maintain 5mph -treadmill matches.

3rd millisecond plane's tire is forced to 15mph to maintain 5mph -treadmill matches.

4th millisecond plane's tire is forced to 20mph to maintain 5mph -treadmill matches.

After a full second the wheels are spinning at 5,000mph.

Again, that's 5mph for one second.

After 45 seconds of accelerating to 180 mph, the wheels would spinning faster than the speed of light.

Two forces that are plied against each other, unconstrained, compounding each other instantly, would become incredibly volatile within seconds.

 

[Notarealsignguy]

Wouldnt the balloon float to the ceiling and friction hold it there during acceleration? It wont just float in mid air.

This is a post I wrote yesterday & I believe it's irrefutable, just read below and tell me how I'm wrong:

Nothing reacts instantly, but let's assume
the treadmill matches speed almost instantly, like in a millisecond (1/1000 of a second) and the plane moved forward at 5mph:
1st millisecond plane 5mph -treadmill matches.

2nd millisecond plane's tire is forced to 10mph to maintain 5mph -treadmill matches.

3rd millisecond plane's tire is forced to 15mph to maintain 5mph -treadmill matches.

4th millisecond plane's tire is forced to 20mph to maintain 5mph -treadmill matches.

After a full second the wheels are spinning at 5,000mph.

Again, that's 5mph for one second.

After 45 seconds of accelerating to 180 mph, the wheels would spinning faster than the speed of light.

Two forces that are plied against each other, unconstrained, compounding each other instantly, would become incredibly volatile within seconds.

First, its hypothetical so if it turns into picking apart the mechanics of it, youd need to question where in the F youd find a giant treadmill that a jet could fit on well before addressing the other questions you posed.
Im not sure why you dont get that these are not 2 forces acting against each other. The spinning of the wheels is not relevant.

 

[Notarealsignguy]

Best video:

 

[Andy D]

First, its hypothetical so if it turns into picking apart the mechanics of it,

I'm not sure how to respond to that.....
After all, it is hypathical "what if" question about physics & mechanics, so I think "picking" apart the mechanics is what it's about..

 

[Andy D]

If the tires could spin faster than the treadmill was running at:
50mph - yes, the plane would take off
100mph - yes, the plane would take off
250mph - yes, the plane would take off
500mph - 10,000 mph, unless the tire exploded, the plane would take off..
But if the wheels speed isn't allow to exceed the speed of the treadmill, the engine's force would cause the nose of the plane to dip, hit the treadmill and flip over.

 

[Notarealsignguy]

If the treadmill was running at:
50mph - yes, the plane would take off
100mph - yes, the plane would take off
250mph - yes, the plane would take off
500mph - 10,000 mph, unless the tire exploded, the plane would take off..
But if the wheels speed isn't allow to exceed the speed of the treadmill, the engine's force would cause the nose of the plane to dip, hit the treadmill and flip over.

I think i see what youre saying. This seems more of a math riddle than physics.
In order for the wheel to move forward, it has to spin at a rate faster than the treadmill. So the speed would exponentially increase to infinity.
Isnt the question flawed then? On paper it would not work because you cant move forward, not because of a physical constraint but by flaw in design of the parameters.

 

[Andy D]

For a plane to be traveling at 200mph on
a treadmill moving at 400mph, the tires would need to be traveling at 600mph.

The only way the ground can go by faster than the speed of the spin of a tire, is when the tire is in a skid... Unless it's on ice or grease, the tire won't allow the plane to move forward.

 

[Notarealsignguy]

For a plane to be traveling at 200mph on
a treadmill moving at 400mph, the tires would need to be traveling at 600mph.

The only way the ground can go by faster than the speed of the spin of a tire, is when the tire is in a skid... Unless it's on ice or grease, the tire won't allow the plane to move forward.

Yeah i realized that was flawed. You cant make assumptions, like ice, or the question isnt the same. The problem on paper wont pencil out. It is saying that A=wheel speed, B=treadmill spead and A=B. In order for the plane to make any forward progress A can not equal B. So its really over right there with no physics involved.
In real life, a>b and the plane would go forward but that more proves that the treadmill wont maintain the same speed as the wheels due to other real world factors.

 

[Andy D]

I think the important distinction people are missing is; the treadmill instantly matches the speed that the wheels are turning, not the speed of the plane.

If the treadmill matched the speed of the plane, the plane would have no problem taking off, assuming the wheels are capable of spinning twice the speed necessary for lift, I read 180mph, so a wheel speed of 360.

 

[Notarealsignguy]

I think the important distinction people are missing is; the treadmill instantly matches the speed that the wheels are turning, not the speed of the plane.

If the treadmill matched the speed of the plane, the plane would have no problem taking off, assuming the wheels are capable of spinning twice the speed necessary for lift, I read 180mph, so a wheel speed of 360.

But if you define speed differently, this all changes. You could argue that the speed of the tire is not the same as rpm. RPM is how fast its spinning, speed is how fast it is moving. In that case a=b until the plane takes off and b=airspeed of the plane throughout the equation.

 

[Andy D]

I think i see what youre saying. This seems more of a math riddle than physics.
In order for the wheel to move forward, it has to spin at a rate faster than the treadmill. So the speed would exponentially increase to infinity.
Isnt the question flawed then? On paper it would not work because you cant move forward, not because of a physical constraint but by flaw in design of the parameters.

I don't think it's a flawed question, either;
A. the wheels would quickly fail
Or, I think more likely
B. The plane would somersault.

 

[Notarealsignguy]

I don't think it's a flawed question, either;
A. the wheels would quickly fail
Or, I think more likely
B. The plane would somersault.

Maybe not flawed but its an impossibility. It defines a=b, its absolute. Then asks can a>b. The answer is no, it cant be equal and greater.
Using actual objects and trying to figure how they would act in the real world is what throws everyone off.
I didnt read the original question well enough, and just saw it as can a plane take off on a treadmill.

 

[GB2]

Once again, the wheels aren't moving forward based on their relationship to the treadmill, be it friction, resistance, wheel speed or whatever....the wheels will move forward because the plane axle is pushing them irregardless of how fast they are spinning or if they are not spinning at all.

 

[Gino]

Wow-wee !!! Seriously, some of you are in the wrong business......... entirely !!! Sounds like some of ya, should be into rocket science. You guys are amazing. What a waste 'y'all are making signs.

 

[Notarealsignguy]

Once again, the wheels aren't moving forward based on their relationship to the treadmill, be it friction, resistance, wheel speed or whatever....the wheels will move forward because the plane axle is pushing them irregardless of how fast they are spinning or if they are not spinning at all.

Yes but the question says the wheels spin the same speed as the treadmill. Re-read it. For forward progress to occur, the wheels have to spin faster than the treadmill, no matter how it is propelled. The question establishes that they cant, therefore the wheels can not move forward. This is assuming that spinning is considered speed.

 

[Andy D]

I think i see what youre saying. This seems more of a math riddle than physics.
In order for the wheel to move forward, it has to spin at a rate faster than the treadmill. So the speed would exponentially increase to infinity.
Isnt the question flawed then? On paper it would not work because you cant move forward, not because of a physical constraint but by flaw in design of the parameters.

I don't think it's a flawed question, either;
A. the wheels would quickly fail
Or, I think more likely
B. The plane would summersalt

 

[Andy D]

Wow-wee !!! Seriously, some of you are in the wrong business......... entirely !!! Sounds like some of ya, should be into rocket science. You guys are amazing. What a waste 'y'all are making signs.

Gino, because I don't recognize sarcasm on Sundays; Thank you...
BTW you're not getting any younger, if you don't want to get arrested in Wal-Mart in about 20 years, because you forgot to put your pants on... These brain teasers might help prevent that.

 

[Notarealsignguy]

Wow-wee !!! Seriously, some of you are in the wrong business......... entirely !!! Sounds like some of ya, should be into rocket science. You guys are amazing. What a waste 'y'all are making signs.

Yeah but look how much more money you can make with signs.

 

[Texas_Signmaker]

Wow-wee !!! Seriously, some of you are in the wrong business......... entirely !!! Sounds like some of ya, should be into rocket science. You guys are amazing. What a waste 'y'all are making signs.

I lost track of this thread after the second post... Only thing I could contribute was an elementary school level drawing of Bernie Sanders.... I hear he is doing well in the polls in Pennsylvania...you must the rallying the troops pretty well up there.