will it take off?

[daTeacha]

Just a couple of points here, gentlemen.

The problem states the conveyor matches the speed of the plane but in the opposite direction. If the plane does not move, neither does the conveyor. The tree sitter cannot simultaneously watch a stationary plane and a moving conveyor. I know this is the basis for most of the fun you are having lately with this thing, but the problem clearly states the plane moves. Not just the wheels, the plane.

I was intrigued by the "time quark" stuff. I enjoy messing with my students minds a bit by telling them that first people thought matter was continuous or analog, then it was eventually shown (to the best of our knowledge) to be made up of small pieces (atoms) which were then shown to be made of even smaller pieces, etc. as we continue to search for the ultimate particle.

Similarly, energy was once considered to be continuous or analog -- consisting of a smooth flow -- then around the turn of the 19th to 20th century was shown to also be made up of pieces (in effect digital), which of course those of you still in this thing will recognize as quanta, whether they be visible (photons) or not.

Then I tell them that sometime before they die someone will find that time is also not the analog thing they perceive it as, but is in fact made up of tiny little pieces. Following that discovery will come efforts to manipulate those little time pieces, which will eventually lead to the ability to travel through time as easily as they now cross the room. Then, just to tighten the screws a little bit, I suggest that the best way to assure that all this happens is for someone from the future to come back here and make suggestions about time being digital, perhaps to aspiring scientists during their formative years.

It takes about 2 or 3 minutes before someone asks me if I'm from the future, to which query I respond with a smile and a non-commital answer.

As a visitor from the future, I can tell you this discussion will continue until the post count exceeds 750. Check back here at that time and remember you saw it here first.

 

[Egon]

This topic is clearly in need of a convention to properly define the problem before setting up another convention to determine who should attend the n ext convention and so on!

Who's got oomph to get funding?

Now I have a faint idea of the planes ability to fly if I am in it. On a bright sunny day with a good weather forecast it will definitely soar into the heavens above. But on a cold windy day with 100 % relative humidity and temperatures at the dew point or slightly below and visibility at about 10 feet I think it will stay on the ground.

 

[MossRoad]

I'm still resisting .....

RESISTANCE IS FUTILE!!! You will run some numbers...

 

[patrick_g]

Nortwest et al, I have and continue to, for the most part, enjoy this thread tremendously. It is my great priviledge to enjoy the company of those posting here. One of the things I have sorely missed after retiring from a DoD (Navy operated) laboratory in civilization (San Diego) and moving to a quite rural area of south central Oklahoma has been just this sort of mental antics and stimulation from and at the hands of my peers and betters.

I was never into pedagogy but was an adjunct prof in evening classes. I taught some classes at the third largest private university in California. My students were university seniors in the computer science curriculum. I taught software engineering and a year long senior projects class. Evening classes were also atttended by a number of adults returning to school with a few more miles on their odometers and were a pretty serious and motivated bunch.

The MCB vs airplane problem was a fanciful one from the start but casting it in real world values is not unwelcome if however limiting.

Theoretically a near constant acceleration of the MCB would generate a force on the plane through the rotational inertial momemt of the rotating landing gear components that could equal and cancell the thrust of the plane, rendering it stationery. That this contradicts or exceeds one of the possible interpretatons of the problem statement is not cause for internecine feuding and warfare.

For this to work we have to assume (along with many other assumptions) that the contact patch of the tires does not have its traction limits exceeded. This is one of the completely valid branches for the discussion to follow but if "real world" concerns like the tires flying apart or the wheel bearings melting is allowed to interfere then the fun is abruptly halted.

I'm not totally convinced that at high speeds (even below hypersonic) that the MCB doesn't pump a lot more air than anyone admitted to, especially if its surface is textured to resemble an actual runway which is hardly trowled to a mirror glaze finish and more so if it resembles black top or gravel.

And now for something completely different (sort of...)

If you are equipped with a desk top decorative but functional style aneroid barrometer, describe,"in theory", how you could use it to measure the height of a tall building without involving the differences in the air pressure at different elevations. I can think of 4 different ways right off the top of my head. Oops, make that 5. There may be more but nothing else seems to be leaping to mind just now.

And, oh by the way I could, "in theory" do the same with a tractor!

As for the coefficient of friction of the Sony HDV 1080i Handycam, it depends! Especially it depends on whether I figure out how to make Windows XP Pro SP-II autoload the input drivers needed (and should have been done automatically) or if I throw the camera off the back porch (12 ft above ground) and see how many times I can hit it with a pump shotgun (Wingmaster 12 ga 3 inch magnum) before it hits the ground. Oh... by the way...l could also measure the height of the tall building with the Handycam (before using it for a clay pigeon.)

One other thing... Did anyone appreciate (I'm not really fishing for a complement) the tow rope and pulley arrangement where the plane's forward motion causes the rearward motiion of the conveyor? I thought it put the setup in a concrete real world framework that anyone could understand wth no further analogies. No magic involved and it fits one of the interpretations (will fly) just fine.

Pat

 

[daTeacha]

At this point, Patrick, based on your admitted proclivity to tug on the occasional posterior appendage of those who are sharing space in this thread with you, I find myself wondering if you have intentionally or accidentally changed the description of the aircraft in question to one made of highly processed wood pulp and miscellaneous fibers. One has to wonder just how high the bovine fecal matter can be piled before it tends to succumb to the incessant tug of gravity and bury its originator.

You said "... rendering it stationery". Shall we now consider the various possible configurations of paper airplanes?

Before we venture further into the potential morass of useless verbosity, let us consider the old adage "Exclusive dedication to necessitous chores without interludes of hedonsitic diversion renders John a hebetudinous fellow."

BTW, most of the ways I immediately think of to measure the building involve the use of geometry and proportions and necessitate that the building be other than the one in which your barometer is located when you use it. Do yours?

I'm more of a Model 12 guy myself -- 16" barrel, Polychoke, 7 rounds of slamfire fun per loading.

 

[patrick_g]

Da Teacha, I guess I am more familiar wilth the guy and call him Jack instead of John. WOOD PULP? I don't feed my stock wood and none have ever stayed in one place long enough to bury themselves in the manner you mention.

I am supremely confident that if nothing self destructed and there were suficient traction at the tires that the MCB could accelerate as required to hold the plane stationery +/- a fraction of a mm. I am as sure of this as I am that the wheels in the (will fly) scenario will be rotating at twice the lift off speed when the gear leave the ground.

Yes ratio and proportion would be one way. If you knew the height of the barometer you could go out in the sunlight and set the barometer on the ground and measure the length of the shadow. Then measure the length of the shadow of the building in question and by similar triangles know the height of the building.

You could also work your way up the stairs counting the number of barometers high the building was and multiply times the barometer's height.

You could also take one of your shoelaces and make the barometer into a pendulum and (in theory) measure the difference in its period at ground level and again at the top and calculate the height.

You could walk to the edge of the roof on top of the building holding the barometer in outstretched hands and release it just as it passed the edge. Then note the distance sideways it went by noting the point of impact. You could use this distance and the known lateral velocity to compute the time of fall and then use the equation
S = 1/gt^2 where g is gravitational acceleration and S is distance to get the building height.

If you had a watch you could have just dropped the barometer and timed its fall.

Here is one that gets into the social sciences instead of physics. You go into the basement and knock on the building super's door. When he answers you say something like, "My good sir, do you see this fine presentation model aneroid baromenter, if you but tell me the height of this building it is yours to keep."

There must be lots of other ways but no good ones leap to miind just now.

Differential UV degradation of the plastic or paint of the barometer is different at different altitudes.

You use the standard lapse rate for temp and altitude and measure the dimensions of the barometer to determind delta Temp and compute delta altitude.

These last two are not favored and any number of other "junkie" ones could be formulated but I would love to get some more really good methods.

Having perfect pitch I can thump the barometer and note the resonant freq at ground level and at the top of the building. The frequency will be changed by the difference in gravitational attraction (relativity) . not a really good one either.

Give it a whorl, maybe someone will come up with some novel and nice alternatives.

Pat

 

[daTeacha]

Well, Patrick, you missed the point of the reference to "stationery", I guess. Here I thought you were trying to refer to a plane made of writing paper (stationery) while talking about one that wasn't moving (stationary). Sigh, another missed opportunity for humor.

I was trying to restrict my uses of the barometer to those not involving precision instrumentation. A watch relying on human reflexes, for example, will not give you a sufficiently accurate means to time the fall of the barometer.

Climbing the stairs and laboriously measuring the height of the building in barometers would work up to a point, but it wouldn't get you to the top of the exterior of the building and is rife with opportunities for accumulating small errors every step of the way, so to speak.

Seeing how far from the building it landed would ignore the slight but present gravitational attraction between the barometer and the mass of the building as it fell, plus it ignores the possibility of Coriolis effect, depending on the orientation of the building. Further, it presumes the building is falt sided from top to bottom, which is rather rare these days.

The tonal variations in the barometer might take something more than even an ear with perfect pitch, but being essentially tone deaf and suffering from partial hearing loss resulting from too much shooting and tractoring without sufficient ear protection makes that whole line pointless for me.

I have students about to come in, so will leave this short.

 

[HTWT]

S = 1/2 gt^2
S = 0.5(32) t^2 or
S = 16 t^2
In Patrick thread missed the 2 when typing

 

[patrick_g]

Da Teacha, Sorry but I am an aural speller (awful speller??) at best. I appreciate the chuckle now that you have explained it to me. I know the diff between paper and being still but didn't note whch word meant which. Thanks.

I noted a sign above the door between the pilot house and the radio room on a Portuguese tuna clipper. It said, "No one aloud in the radio room." I figured it was library rules so my bud and I whispered while there checking out the radio and sat nav.

My wife still kids me about a note I sent her over 40 years ago with rabbit spelled rabit.

My claim to fame is not in being a good speller. I think that the writers of the best spell checkers deserve the Nobel prize.

I am a graduate of the Christopher Columbus school of touch typing where I look for, discover, and land on the keys one at a time. Frequently they are the key I want but are the wrong key. Other times my larger than standard fingers hit multiple (or wrong) keys even when I know the right key.

I took a typing class in the USAF and the final "graduation" exercise was a speed test where I scored 15 WPM before correcting for errors. I can copy morse code faster with fewer errors in all caps long hand with a pencil!

About your objections regarding error and precision of my suggested measuring techniques... what part of "IN THEORY" do you need explained in detail?

One other thing... I tend to forget to

Pat

 

[daTeacha]

You need some guidelines regarding accuracy and precision else you could just look at the barometer, then at the building, and guess its height based on your visual estimate of how many barometers tall it appears to be. -- sort of like a forester using his Biltmore stick but with a lot less accuracy. For that matter, you could use your thumbnail like a Biltmore and get some vague idea, too.

Which in a roundabout way brings us back to the original problem, I think.

We really need to define what is meant by motion of the plane. I maintain that motion OF the plane is not the same as motion within the plane. I.E. the whole thing has to move to be counted as motion. Therefore, if it can move at all, it can move enough to lift off, unless one insists on claiming the wheels are being rotated by the engine as in a tractor rather than by friction with the ground.

Both of my analogies (the rubber band and the dyno) were attempts to emphasize the point that the motion of the plane as a whole is caused by something other than the motion of the wheels. Rather, the wheels turn as a result of the motion of the plane. The wheels could turn (on a dyno for example) without causing the plane to move enough to fly. Conversely, the plane can fly without regard to the motion of the wheels on the dyno, which is nothing more than our MCB wrapped around a cylinder.