studiot

One of these two statements can't be correct. Like KipIngram I am still waiting for a reasonable response to my offered helpful discussion. I sincerely hope the above extract does not mean you are saying you actually made no mistake, just admitted one for convenience.

Thank you for your comments. Do you have any references please?

Thank you both for you contributions.

You started off talking about a 'plasma cushion', now you are talking about a cloud of electrons so which is it? And while you are at it please address my queries about traffic dynamics. For instance you now say that the machine will have to be confined to special road. So how would I get home, or are you proposing laying this system everywhere, replacing all the existing roads? If you do this how will pedestrians, ladies with prams, dogwalker, cyclists, horseriders etc get about? How much will it cost? Can you have more than one vehicle an the track at a time (you can't with maglev or any train for that matter)?

You are clearly are interested in Chemistry, but you still haven't said why this is in homework? I fully endorse what OldChemE said and you should look up the terms if you have not met them. It is Free Energy (and in particluar Gibbs free energy as there are several types) that are the thermodynamic potentials that allow a reaction to happen spontaneously, not enthalpy alone. Free energy is a combination of enthalpy and entropy. Note I said spontaneously because it may well be possible to force a reaction by adding energy. Further, the free energy says nothing about the rate of said reaction. Just because a reaction is thermodynamically possible, it does not mean it will go very far because the rate may be so slow as to be negligable. For example silica is soluble in water, but over a timescale of tens of millions of years. OK back to your particular quest. There is nothing more satisfying than working something out for yourself. I had hoped the hint link to Wiki would cause you to realise the solubility of (ammonium) nitrate as you looked down the page and then you might also see the other information presented. As noted, group 1 or the alkali metals groups compounds are generally very soluble, as are ammonium compounds. But group 2 or the alkaline earths have many insoluble compounds. This fact is often used in schemes such as yours to precipitate the unwanted ions. I said you are using the wrong reagents. So here is a scheme mixing a soluble calcium compound with a soluble ammonium compound to produce an insoluble calcium compound. [math]2NH_4^ + \left( {aq} \right) + SO_4^{2 - }\left( {aq} \right) + C{a^{2 + }}\left( {aq} \right) + 2NO_3^ - \left( {aq} \right) \to CaS{O_4} \downarrow + 2\left( {NH_4^ + + NO_3^ - } \right)\left( {aq} \right)[/math] Did you notice the way I wrote the equation, showing the precipitate? Note also that charges must balance as well as atomic proportions when you right an equation like this. And also that you need to find suitable soluble/insoluble pairs to make the scheme work? Edit A final word of caution since you are actually doing practical work. although ammonium compounds in solution are pretty safe, Ammonium nitrate is not the only explosive ammonium compound.

Some think in words, some in pictures, some in concepts and I'm sure there are other ways I've missed. I also believe that most have some combination of these, with a dominant mode. The point I wondered was has any work been done to establish if for example the group who think predominately in pictures have a higher incidence of visual halucinators.

Basic transportation mechanics is often forgotten with these 'futuristic' systems. Notably, once you have levitated something, how do you safely drive it forwards in a crowded street?

Any more comments like this in one day and you are going to crack me up. +1

Like building on floodplains and vulnerable coastal margins?

Concentration is the right word. It is not an interference phenomenon. If it was then reinforcement would be the right word for constructive interference. It is a simple matter of focusing or collecting or - yes - concentrating all the available power into the region within the horn. Normally sound would be emitted in all directions. So if the volume of the horn was 1/16 (typical) of the volume of a sphere then you might expect a concentration of 16 times. This will not be achieved in practice because of (friction) losses at the surfaces of the horn. You are right that the (electrical) power matching can be better than 90% efficient for an electrical transformer. A horn will not achieve anything like this 30% being very good indeed. I did not link to any articles on acoustic impedance or horns. I assume you can look these up for yourself, but please ask away any further questions.

+1

Have you ever taken an A level English Literature paper? The rest of post#4 is good.

I so..ooh wish that were true.

Of course there is. I can (just about) play a game of badminton (with a little help from my friends) But I couldn't name one badminton star, tell you the height of the net or the size of the court or most of the rules. High school science is better than that. It allows you to participate in technical discussion and appreciate what is going on (with a little help from your friends)

The simple fact is that you are using the wrong salts. What you have not said is why this is in Homework Help ? You have certainly complied with the special SF rules in this section in that you have shown an attempt. Unfortunately you have also quite rudely resisted attempts to help you. Remember that we do not do you homework for you, just help you complete it.

Sorry no,there is no amplification. For there to be amplification there would have to be energy.power source adding energy to the sound wave. Yes concentration is a good non technical word but I think you know enough electronics to understand the technicalities. Any sort of funnel shape acts as an acoustic transformer in much the same way as a line transformer is used in audio and public address engineering to match the impedance of the line signal to the loudspeaker or the microphone signal to the line. The ear and the gramophone pickup have a higher acoustic impedance, which is (better) matched by the narrow end of the funnel and the free air has a lower acoustic impedance which is better matched at the wider end. The flared shape is the most efficient to reach the optimum diameters smoothly and quickly. These are known as horns, after musical instruments that also operate on this principle.

But this is not what you originally said. Originally you said the above applies to any rotation (around a central point but what other sort of rotation is there?) Later you changed this to a fixed central point, without defining fixed. So I have a list of excluded examples of systems to which your statements can be applied , but no included ones. You have not provided a single example of a single system to which your analysis applies, despite several requests for one. So I have explored a number of examples of genuinely rotating systems with you, and you have rejected all of them as not analysable by your method. You are adamant that it is applicable to a system with a centre that is fixed or not going anywhere, yet you are equally adamant that this system with zero translational velocity has a momentum (note not angular momentum) How is this possible? You claim that the generally accepted principle is that momentum should change if the radius changes. But the system, by definition, has no momentum to change. It only possesses angular momentum. I have no idea what books you have been reading about mechanics, but your opening statement suggests to me that you have only partly understood them. In particular it is true that the most common cited example of the effect you describe incorrectly is that of the skater spinning on the spot. The skater's angular velocity increases as she draws her arms inwards. She has no momentum because she is spinning on the spot, but she has angular momentum, which remains constant (is conserved) so as the radius decreases the angular velocity increases, just as you say. But her momentum does not increase, which is not as you say. This is all possible because of the very low friction on ice so we assume no driving forces are required. In the case of carousel or weight on the end of a rope, a driving force is required. And this must be included in the system for analysis, which you are not doing, but everyone here is telling you that you need to do. We have been trying to help you create a correct analysis of rotating systems that can be applied as widely as possible, not one that has to exclude every example that is presented. Since you have obviously already put in a great deal of effort into this, I can only urge you to study some basic mechanics texts. I suggest engineering science ones would be better as they are more self contained and plain speaking than applied maths or physics ones which also rely heavily on a whole raft of peripheral background material. This would help you understand when momentum and /or angular momentum is destroyed and when they are conserved and how to include all the necessary items in a system.

1) Enthalpy has nothing to do with it. (please note correct spelling of the term) 2) I suggested you look at the solubility of sodium and potassium sulphates, since your proposed reaction equation shows them precipitating. Yet you report the solubility of potassium nitric acid in water? If you don't understand the significance of these solubilities you should not be fiddling with any quantities of these chemicals and I am not going to tell you.

There is more than a mistake in your thinking, there is a fundamental misunderstanding. Your stipulation concerning rotation about a 'fixed point' just won't wash. Consider the following. Somerset is famous for the largest nightime illuminated carnival in the world. This is made from hundreds of floats which are made from enormous low loader lorries. Mounted on these lorries are carousels, roundabouts and other rotating mechanisms, carrying carnival actors. Now tell me that your analysis debars these actors from claiming that these carousels rotate about a fixed point whilst spectators on the sidewalks claim the point is moving along on the back of a lorry. There is a considerable amount you clearly don't know so rudely telling a bunch of folks with Phds in engineering and/or physics that they don't know what they are talking about and only you are correct is in my view confrontational. The sad thing is that your formula can be applied (if done correctly) to these carousels or my wheel, but your are refusing to allow that anyone else knows anything. In more advanced mechanics this issue is resolved by means of one of two methods that of Lagrange or that of Euler, one of which takes the view of the spectator the other the view of the carousel actor. Have you heard of these?

+1 I was not I who chose this confrontational approach to the discussion. I far prefer cooperation and pooling of knowledge. You may like to know that both my questions were very very simple examples of the sort of calculations engineers do every day when considering the complicated dynamics of machinery and in fluid mechanics in general. This would include deriving suitable equations to describe the motion of moving parts and the forces (and moments) they exert upon one another. I come back to this point about conservation being a system property not an equation property. The same problem bedevils another field entirely - that of Thermodynamics. So many would be engineers fail simply because they do not properly identify the system.

So can I take it you are denying that a wheel rotates about its hub?

I know that. That is why I said that you did not say it. It is also why I did not accuse you of it, or contradict you. What I think you mean is that some truths are absolute. In which case one counter example is insufficient. But I did observe that you chose a poor example in mathematics since it is not about about 'absolute truths. And I gave an example of the mathematics of where the truth varies according to the conditions. It would be really nice if you could be bothered to acknowledge my posts properly and accurately, especially as they seem to be the only ones offering you any support.

You have to upload and attach them first. Use "More reply Option" Then look at the bottom of the window where it says Attach Files and then "Choose Files" When you have uploaded the picture file of interest click in your typing in window where you want the picture to appear and then click on "attach file", against the one you want. Not that when uploading several pics (you can do several at once) it may not upload in the order you ask.

What do you think the phrase means?

Neither is conserved. The conservation laws apply to a system, not an equation. This is why I have been trying to get you to describe your system. Consider the following system. A light, stiff, circular hoop is rolling along a flat horizontal ground surface with forward velocity v. Attached to the circumference is a mass point P. What are the angular and linear momenta of P 1) At the point of contact with the gorund 2) At the top of its travel around the hoop. Why are they different? How this fit with your equation and conservation?