studiot

Do you mean these? (extracted from the Wiki article in davidivad's post) "connected at both ends by shorting rings forming a cage-like shape" These are simply there to electrically connect all the induction bars together in parallel. Do you mean a shaded pole motor? http://en.wikipedia.org/wiki/Shaded_pole_motor Pole shading is one of many starting methods employed, but we haven't got to these yet. The thing to remember with induction motors is that a three (or more) phase motor will start on its own and many textbook explanations only treat 3 phase. Most domestic supplies are single phase and require an auxiliary starting mechanism or the rotor would simply turn to assume the position of minimum energy and stick there. Starting methods include additional windings, additional components (capacitors and/or inductors) to generate a phase shifted alternating signal or phase from the main supply so that there is a 'side push' as well as the main one. Shaded poles are deliberately partially shorted to create an imbalance in the rotor response to the magnetic drive which again starts the motor.

Or we could just admit that we don't know.

I would have thought that the author of this thread was the sort of member we are seeking to attract, as opposed to crackpots. http://www.scienceforums.net/topic/86844-problem-314-turcotte-and-schubert-geodynamics/ So what went wrong? I saw the author listed as viewing the thread when I made the second post the following day so he did not just flit through.

There are two aspects to this. Godel says that within any formal system there is at least one proposition, that can be made with the axioms and definitions of the system, but that cannot be proved within that system, yes. But Did I just mention axioms and definitions? In order to have a formal system you must start with some axioms - no axioms no system! Further again you require definitions to specify your axioms -These again have no 'proof', just plausibility or convenience. Both the axioms and the definitions are separate from and additional to any Godel unproven propositions.

On a more technical note than discussing terminology, Earthquakes in general generate periodic forcing functions to structures. At or near resonance responses by the structure is another cause of failure. Have you investigated the effect of this on your system eg by the Fowkes and Mahony equation (1994)?

Looking in the opus citatus I see you are studying section 3.10, where the necessary theory is developed. Are you attempting all the questions 3.12 through 3.15 or just 3.14? The actual formula you need is not stated in section3.10, although similar situations are discussed, but the formula you need is the subject of question 3.13. Are you bothering to come back to SF? There is a lively Earth Science section, with several knowledgable members.

Yes indeed, which is why I mentioned him and Erlangen (which failed but was not fruitless in the end) as an addition to your post#4. Erlangen was the Hilbert's program to codify mathematics. It is also true that Russell, Whitehead and particularly Hilbert developed much deep logical thought of great subsequent value in the searches for their particular grails. We owe much to each.

This is a prime example of where hand waving explanations break down in the face of hard facts. Actually the entropy at 0oK need not be zero. Atkins give the value of 0.21 JK-1 per gram for solid carbon monoxide, both experimentally measured and theoretically derived. The mechanism is due to random variations of orientation of the molecules.

Time and change are closely associated, but they are not the same. You can have one without the other. But to only be prepared to discuss or condiser time in relation to change is blinkered thinking. We use time (and) for other purposes. Take, fo instance, the Rodistochrone problem. Two hungry mice stand in their cages at 10m and 30m distance from the cheese. At the starter pistol the cages are opened. Which mouse eats the cheese? Time is being used here for comparison, not change. Now let me make a change; I remove a leg from one mouse. Which mouse gets the cheese? Temperature (with a large T) is another quantity we introduce to make comparisons like time (with a small t).

David Hilbert and Erlangen?

Have a care with this argument. Entropy 'extracted' is defined as the heat extracted, (not the energy) divided by the absolute temperature of that extraction so extraction at 0o leads to a division by zero singularity.

Good morning Artorius. I do not know your background so I don't know what you should know about this question. I can confim that if I take the acceleration due to gravity as 10 m/sc2 then I get the figure of 0.405m, using the simplest beam theory. That is dividing the plate into 1mete wide strips and considering each strip as a separate beam. So lets start at the beginning What do you understand freely supported to mean? If you can state in words what you think might be happening, perhaps together we can convert that to math.

Yes Amperes Law.

You can carry my logic all the way in from the outside, as I said before, working B, then D then finally C using the carry conditions each time. I made a start of B for you in post#17

Here is the next stage of my reasoning; I have already indicated that A must be 1 or 2. Now consider multiplying E by 4. E is the only digit that does not entail a potential carry digit, so the result of the multiplication of the whole number by 4 has the same last digit as 4E. The result of the multiplication must end in either 1 or 2, since the last digit of 4E = A But there is no number such that the last digit of 4E can be 1 so A must = 2. So 4E ends in 2. There (4x3=12) and (4x8=32) both end in 2 so E is either 3 or 8 Since A = 2; (4A + carry from 4B) can only be 8 or 9, But we are told the leading digit is E so E = 8. Since E = 8 there is no carry on multiplying B by 4, so B must be either 0, 1 or 2

Sorry it's so scruffy, but assuming your stator field is rotating anticlockwise and the instantaneous mag field is as shown; The induced current in the cage wires (shown in section as small circles around the rotor periphery) are given by the right hand rule, crosses into the paper and dots coming out of the paper. The current in a rotor conductor generates a circular field round it, like any current carrying conductor, which reinforces the statorfield on the right and weakens it on the left of the conductor. This is equivalent to a force turning the rotor in the same direction as the stator field rotates. This jiggle in the field is shown in diagram 2.

I'm sorry but you cannot legitmately pick and choose what energies you will include or not include in your energy balance. Work is done on a rising body by the force causing it to rise. The force causing it to rise is not a single force but the resultant of the vector addition of several forces. Some of this work goes into the kinetic energy of vertical motion. (did you remember that?) Some goes into the increased gravitational energy. If the body is not rising there is another force acting, which is the equilibrant to the lifting resultant. Similarly if the body is in level flight the drag will be doing work on the air, leaking kinetic energy away to the air. This KE is maintained by the power of the engine supplying the thrust, which does work on the body. So the engine is continually supplying energy to the body. This energy supply is enough to also power any vertical gain in PE or KE that happens, but the exchange is via the kinetic energy of the body. So there is no energy balance crisis. If the thrust ceases then the body will eventually fall, not rise. It may be possible to temporarily take advantage of the combined lift and drag vectors and upwelling air to glide for a considerable distance. But the glider will eventually return to earth.

No problem with the frictionless model. I wondered if you were thinking of an airfoil mounted on some sort of jet or rocket sled. But remember MigL's four horsemen: Horseman 1 The sled's weight has to be added to the foil's weight. That immediately makes the rising foil different from the non rising one. Horseman 2 You cannot ignore thrust Horseman3 Yes some effort is lost in drag. This energy loss heats the air Horseman4 Whatever is left over becomes lift. HiHo Silver! I'm trying to concentrate on the major parts and keep out the difficult bits.

Sometimes doing an energy balance make things easier, sometimes it makes them more difficult. In the case of flight, energy balances are not as helpful as direct consideration of the forces involved. Much of what you say is correct, but your description of the held down airfoil is lacking. What holds it down? You need to include any hold down forces acting in your analysis. You have shown the 'non-rising' airfoil as moving forwards. How is it driven forwards at the same time as being held down? Address this and you will find the resting place of your misplaced energy. Bouyancy forces act on immersed bodies whether they are moving or not, but they are additional to any lift forces that act due to the motional interaction of the fluid and the body. For most practical airfoils bouyancy forces are small to negligable compared to the weight of the foil, but in hydrofoils they can be significant.

A hypothetically perfect engine is called a carnot engine, and carnot engines cannot produce motion without also producing heat, unless they violate the Second Law. We are happy to disuss and help you resolve your questions, but since we know more physics than you do, how about letting us suggest things? For instance there is nothing wrong with considering your ball thrown into the air as an isolated system, in fact it is an excellent model for many purposes. But then your ball does not posses a jet engine and a fuel tank. The important thing is to know where to draw your boundary around your system. A good choice makes the analyis (relatively) simple. So perhaps you would be kind enough to reiterate your question in plain terms, shorn of all the extra paragraphs you started with.

Another misconception is your use of the term bouyant force. The aerofoil is subject to bouyancy forces, but these are nothing to do with the lift and drag forces generated by airfoil action.

Specifying the whole universe as your isolated system offers more difficulties than it solves. Not least being that we do not know is the universe is finite or infinite. If infinite standard conservation has no meaning. Incidentally you need to be careful saying you understand The First Law (conservation) and then producing statements like this one. I always thought that the large part of the chemical energy went into heat in an engine of any sort.

Indeed it is. Do you know the full principle? In any isolated system total system energy is conserved. So what is your isolated system? You did ask where your thinking was going awry. Incorrectly specifying the system is a very common error.

Why do you think energy must be preserved? Isn't a continual input of energy the job of the engine?

There's invariably more than one method in these things and the real fun comes in seeing how someone else has done it.