Airplane on a Conveyor Belt...

[eskimo2]

Originally posted by john9001
eskimo2, i think you are putting too much emphasis on the amount of energy required to spin a wheel, but to answer your question, bob's plane will take off in 99 feet and 11 inches and chucks plane will take off in 99 feet and 10.5 inches.

As it applies to the question where the conveyor exactly matches the plane’s speed; the difference is so slight that it wouldn’t hardly matter.  The plane will take off almost exactly within the same distance.

The original AH BBS thread question said: “the conveyor exactly matches the plane’s wheel’s speed”.  This changes everything.  In this instance, the conveyor must assume an accelerate rate that loads as much rotational energy into the ever increasing wheel speed to match the thrust of the engine/prop.

[eskimo2]

Originally posted by rabbidrabbit
Me.

I'm just that fricken evil.

OMG!  Did you make the change with the twist to the solution in mind?  Or was it accidental?

[BlkKnit]

the conveyor exactly matches the plane’s wheel’s speed”. This changes everything. In this instance, the conveyor must assume an accelerate rate that loads as much rotational energy into the ever increasing wheel speed to match the thrust of the engine/prop.

This is not possible.  The wheels only rotate upon movement of the aircraft.  If the aircraft can move, it can develop lift.  If the belt matches the speed of the wheels EXACTLY then the wheels can never spin to start with because the aircraft has not moved.

Hey!  this is fun?

[2bighorn]

Originally posted by eskimo2
How did the rotational inertia and energy now stored in Bob’s and Al’s wheels affect the take off distance of their planes?
We know that Al’s plane will still take off in exactly 100 feet; where will Bob’s and Chuck’s planes take off?

Please, tell the answers and explain in such manner, that dumb people like me, will understand. Pretty please....

[AKIron]

Originally posted by BlkKnit
This is not possible.  The wheels only rotate upon movement of the aircraft.  If the aircraft can move, it can develop lift.  If the belt matches the speed of the wheels EXACTLY then the wheels can never spin to start with because the aircraft has not moved.

Hey!  this is fun?

I think it is assumed that the belt must only try to match the wheels speed and be successful to within say a few nanometers per second. For the umpteenth time (not directed at anyone in particular), which speed? The forward speed of the wheel as measured at the center point of the axle or the speed of the wheel as measured at the surface of the tire? These two will yield dramatically different results.

[Yknurd]

My brain hurts.

[BlkKnit]

Just my opinion here, but it seems that many of the "restrictions" placed on this myth (yes, myth) are physically impossible.

Belt matches plane speed, then so what, wheels turn twice as fast and the plane takes off.

Belt matching wheel speed (outside of the tire circumference) is impossible.  Something will be different (unless there is no movement at all). The only thing that will make the tire spin (and thus the belt) is if the plane is moving.

IF there is just a plane, sitting on a free wheeling conveyor belt with no outside forces applied to the belt or the tires, the tires will not necessarily turn at all!  However, the plane will still take off because the belt will move WITH the aircraft.

[eskimo2]

Originally posted by 2bighorn
Please, tell the answers and explain in such manner, that dumb people like me, will understand. Pretty please....

Chuck’s wheels have no mass, and no rotational energy.  Bob’s wheels have half the mass of Al’s wheels.  Therefore, at 50 mph Chuck’s wheels are storing 0 energy, Bob’s wheels are storing ½ X energy and Al’s wheels are storing X energy.  Chuck’s plane must take off first, then Bob’s, then Al’s.  It doesn’t matter if Chuck’s plane takes off 4 feet before Al’s or 4 mm; the concept shows that getting the wheels up to speed consumes energy.  A conveyor belt of unlimited speed and power can constantly load enough energy into the wheels to counter-act the plane’s thrust.  

Note: this ONLY applies to the question where “the conveyor exactly matches the plane’s wheel’s speed”.

Also note: After the plane runs out of gas, the energy stored in the wheels would be equal to the energy consumed by the full tank of gas (minus the inefficiency of the engine and prop, etc.).

[eskimo2]

Originally posted by BlkKnit
Just my opinion here, but it seems that many of the "restrictions" placed on this myth (yes, myth) are physically impossible.

Belt matches plane speed, then so what, wheels turn twice as fast and the plane takes off.

Belt matching wheel speed (outside of the tire circumference) is impossible.  Something will be different (unless there is no movement at all). The only thing that will make the tire spin (and thus the belt) is if the plane is moving.

IF there is just a plane, sitting on a free wheeling conveyor belt with no outside forces applied to the belt or the tires, the tires will not necessarily turn at all!  However, the plane will still take off because the belt will move WITH the aircraft.

Imagine that “exactly matches” really means that YOU have a big acceleration control dial for the conveyor and your job is to keep it in place.  The plane fires up and begins to inch forward; you see this and crank the acceleration dial.  You go too far, however, so the plane drifts back behind its starting point.  Seeing this you back off on the acceleration dial and adjust it to keep the plane pretty much where it started.

Look at the concept; don’t get caught up in the semantics of the word “exactly”.

[2bighorn]

Originally posted by eskimo2
Chuck�s wheels have no mass, and no rotational energy.  Bob�s wheels have half the mass of Al�s wheels.  Therefore, at 50 mph Chuck�s wheels are storing 0 energy, Bob�s wheels are storing � X energy and Al�s wheels are storing X energy.  Chuck�s plane must take off first, then Bob�s, then Al�s.  It doesn�t matter if Chuck�s plane takes off 4 feet before Al�s or 4 mm; the concept shows that getting the wheels up to speed consumes energy.  A conveyor belt of unlimited speed and power can constantly load enough energy into the wheels to counter-act the plane�s thrust.

No offence, you just say it happens and I'd like to know how and why.

What I'd like to see is the clear answer on your very specific question:
How did the rotational inertia and energy now stored in Bob�s and Al�s wheels affect the take off distance of their planes?

Originally posted by eskimo2
Note: this ONLY applies to the question where the conveyor exactly matches the plane's wheels speed.

There is no conveyor in your identical triplets story. Got to read it again. Maybe I've missed something.

Originally posted by eskimo2
Also note: After the plane runs out of gas, the energy stored in the wheels would be equal to the energy consumed by the full tank of gas (minus the inefficiency of the engine and prop, etc.).

Interesting, very very interesting. I must admit I didn't know that.

[AKIron]

Originally posted by 2bighorn
No offence, you just say it happens and I'd like to know how and why.

What I'd like to see is the clear answer on your very specific question:
How did the rotational inertia and energy now stored in Bob�s and Al�s wheels affect the take off distance of their planes?

 There is no conveyor in your identical triplets story. Got to read it again. Maybe I've missed something.

 Interesting, very very interesting. I must admit I didn't know that.

uh oh, here comes the belt sander

[eskimo2]

Originally posted by 2bighorn


 There is no conveyor in your identical triplets story. Got to read it again. Maybe I've missed something.
 

The conveyor belt is the confusing part.  This question allows the reader to understand the principle of rotational acceleration consuming power without the conveyor.  Understand this, and you should then be able to transfer the concept to the conveyor question.

[eskimo2]

Originally posted by AKIron
uh oh, here comes the belt sander

LOL, OK



http://hallbuzz.com/movies/wheel_on_sander_250th.AVI


http://hallbuzz.com/movies/paper_treadmill.AVI

[2bighorn]

Originally posted by eskimo2
The conveyor belt is the confusing part.

Indeed, even after third reading, I still don't see conveyor in that story

Originally posted by eskimo2
This question allows the reader to understand the principle of rotational acceleration consuming power without the conveyor.

The principle which you resist to explain.

Originally posted by eskimo2
Understand this, and you should then be able to transfer the concept to the conveyor question.

I'd really like to, but I need your help, and the best way to help me, would be to answer your own question:
How did the rotational inertia and energy now stored in Bob's and Al's wheels affect the take off distance of their planes?
Since you understand the principle (and you're a teacher), it should be easy to explain (I'd really like to know).

[AKIron]

Originally posted by 2bighorn
Indeed, even after third reading, I still don't see conveyor in that story

 The principle which you resist to explain.

I'd really like to, but I need your help, and the best way to help me, would be to answer your own question:
How did the rotational inertia and energy now stored in Bob's and Al's wheels affect the take off distance of their planes?
Since you understand the principle (and you're a teacher), it should be easy to explain (I'd really like to know).

Energy transferred to the wheels is energy not used to move the plane forward.