Airplane on a Conveyor conundrum

[Chillitt]

Db look at the question again...
The conveyor moves in the opposite direction to the plane, but at the same speed. If, as you say, the plane isn't moving, then nor is the conveyor belt...

[Slugsie]

ive explained it :/

completely wrong. i say your wrong, because you state that the plane speed is measured by its ground speed. this is the speed its moving relative to the ground. if the conveyor is going the same speed as the plane but reverse or to put it another way -10mph, it will be going the same speed as the ground.

10mph + -10mph = 0mph,

No, if the airplane is moving forwards at 10mph relative to the ground, then the conveyor is moving backwards at 10mph - relative to the ground. That is the whole point. You can't measure one thing (the aircraft) relative to the ground, and the other thing (the conveyor) relative to something else (presumably the plane in this case).

Also, the 10mph + -10mph = 0mph is the wrong maths. What that is showing is that their average speed of the system (the plane and the conveyor) is zero. You measure their relative speed by looking at the number of 1mph steps there are between +10mph and -10mph, and there are 20 of those, so their relative speed is 20mph.

If you and I stand back to back, one facing north, and one facing south, then we both walk forward at 5mph, then we have a relative speed to each other of 10mph.

[dieselboy]

eh?

thats what happens... i can try and explain it again..

[dieselboy]

Db look at the question again...
The conveyor moves in the opposite direction to the plane, but at the same speed. If, as you say, the plane isn't moving, then nor is the conveyor belt...

well, at the same speed but in the opposite direction.
this would mean the same speed, but a negative
eg. -10mph (minus ten miles per hour)

so yes, if the plane is stopped then so has the conveyor. but this dont help lol

[Slugsie]

yes but the forced produced is only enough to keep the plane at 200mph, or else it would accellerate

Yes, your point being?

but this doesnt help you understand that this is a trick question, and that the ground and the conveyor belt both move away from the plane at the same speed the plane is moving away from them, except only the opposite direction.

No, it is not a trick question. The conveyor is moving, it states so right there in the question. It has a speed relative to the ground that is the same as the aircraft.

If the conveyor doesn't move, then it has no effect on the system that a normal runway already doesn't already have. Therefore by your own argument you agree that the aircraft flies.

[nero279]

thats what happens... i can try and explain it again..

not in my world it don't,

that would mean my 2.4 does 45mpg but i just don't know it because as i drive away from home, home drives away fom me so we end up twice as far apart as what i've driven.

So i drive the 70 miles up the A20 into london, but when i get there i'm actually 140 miles from home is what you're saying?

[dieselboy]

No, if the airplane is moving forwards at 10mph relative to the ground, then the conveyor is moving backwards at 10mph - relative to the ground. That is the whole point. You can't measure one thing (the aircraft) relative to the ground, and the other thing (the conveyor) relative to something else (presumably the plane in this case).

Also, the 10mph + -10mph = 0mph is the wrong maths. What that is showing is that their average speed of the system (the plane and the conveyor) is zero. You measure their relative speed by looking at the number of 1mph steps there are between +10mph and -10mph, and there are 20 of those, so their relative speed is 20mph.

If you and I stand back to back, one facing north, and one facing south, then we both walk forward at 5mph, then we have a relative speed to each other of 10mph.

yes but now your are changing the whole thing.
i think you are confused.
if above is now the situation, then the plane wouldnt take off at all.
but above isnt the situation. and the plane will take off, but the conveyor wont move.

and as you say, you cant measure speed of one thing and then the speed of another against something esle.. well why does your first post say this.

your first post says that the plane moves forward relative to the ground.
the conveyor moves relative to the plane but the opposite...

here we have two measurements of two things of two points.

so plane moves 10mph measured by the ground.
this means that the ground underneath it is going the other way -10mph relative to the plane.
if you were looking out the bottom of the plane, and didnt know you were moving, you would say that the ground is moving at 10mph. not 20.

so because the conveyor is also moving the same speed as the plane but the opposite way, then the conveyor and the ground are going the same speed. which means they are both going 0mph (zero, zilch, nowhere)

this is because the ground does not move like this.

[dieselboy]

not in my world it don't,

that would mean my 2.4 does 45mpg but i just don't know it because as i drive away from home, home drives away fom me so we end up twice as far apart as what i've driven.

So i drive the 70 miles up the A20 into london, but when i get there i'm actually 140 miles from home is what you're saying?

no not at all. i can see your confusion.

if you drive 70 miles up the a20, you are 70 miles from home.
or, your home is 70 miles from you.

you dont add the two together.

[Sancho]

not in my world it don't,

that would mean my 2.4 does 45mpg but i just don't know it because as i drive away from home, home drives away fom me so we end up twice as far apart as what i've driven.

So i drive the 70 miles up the A20 into london, but when i get there i'm actually 140 miles from home is what you're saying?

What you should do is just get in and wait for your house to move away and London to approach. It'll save you a fortune.

[dieselboy]

Yes, your point being?



No, it is not a trick question. The conveyor is moving, it states so right there in the question. It has a speed relative to the ground that is the same as the aircraft.

i think youve almost got it!

If the conveyor doesn't move, then it has no effect on the system that a normal runway already doesn't already have. Therefore by your own argument you agree that the aircraft flies.
well yes, for about the 20th time, the plane will take off

the plane will take off, but not because it overpowers the conveyor, its because with those conditions, and how the conveyor moves exactly the same speed of the plane but negative therefore the conveyor is actually stationary

[dieselboy]

What you should do is just get in and wait for your house to move away and London to approach. It'll save you a fortune.

no sancho

[Sancho]

This is tickling me. I'm supposed to be working.

[Slugsie]

yes but now your are changing the whole thing.
i think you are confused.
if above is now the situation, then the plane wouldnt take off at all.
but above isnt the situation. and the plane will take off, but the conveyor wont move.

Nope, not confused at all. I think that you are mis-reading the question.

and as you say, you cant measure speed of one thing and then the speed of another against something esle.. well why does your first post say this.

It doesn't. Read the question again.

your first post says that the plane moves forward relative to the ground.
the conveyor moves relative to the plane but the opposite...

Nope, doesn't say that at all. It says that it matches the speed, but goes backwards. That is not the same as 'moves relative to'.

here we have two measurements of two things of two points.

so plane moves 10mph measured by the ground.
this means that the ground underneath it is going the other way -10mph relative to the plane.
if you were looking out the bottom of the plane, and didnt know you were moving, you would say that the ground is moving at 10mph. not 20.

so because the conveyor is also moving the same speed as the plane but the opposite way, then the conveyor and the ground are going the same speed. which means they are both going 0mph (zero, zilch, nowhere)

this is because the ground does not move like this.

But the conveyor is also moving relative to the ground. As you say, you can't measure their speeds relative to different things.

However, I also contend that it doesn't matter what you measure the conveyors speed relative to, the conveyor will have zero affect on the airplanes ability to move forward, achieve airspeed, and fly.

[dieselboy]

This is tickling me. I'm supposed to be working.

sorry, i will put the feather away.


did you like it by any chance?

[Chillitt]

so because the conveyor is also moving the same speed as the plane but the opposite way, then the conveyor and the ground are going the same speed. which means they are both going 0mph (zero, zilch, nowhere)

this is because the ground does not move like this.

If the conveyor is moving, it cannot be be going at the same speed as the ground!!

Lets, just for the moment, measure the speed of everything, relative to the ground.
to start, the plane is not moving, the belt isn't moving, the engines are not even running.
The engines start, the plane moves, lets say North.
the belt moves south.
the plane is now doing 10mph north. the belt is going 10mph south. so the wheels are doing 20mph.
The plane accelerates, to say 200mph - it's take off speed. the belt is now going 200mph the other way. the wheels are doing 400mph.
the plane takes off because the plane is moving relative to the ground and, as according to the original question, the is no wind, it is moving through the air at 200mph so it will take off.
there is absolutely nothing about the wheels doing 400 mph or the belts movements that can prevent the plane flying