studiot

Nevr reread over one of your old posts. It just makes you cringe how crappy your spellung is.

I am going to go right back to the beginning and start again. I shall work through your proposition a line at a time trying to knock it into proper shape so you don't end up with fallacious conclusions. You are welcome to come along for the ride, you never know you may learn something to your advantage. So the first line "Both angular momentum and momentum are accepted to be conserved values" This, like many of your statements are half truths. I am sure this is unintentional and based on inadequate study material. Are accepted ?? by whom ?? Are conserved values ?? Always?? What is meant by a conserved value in this case?? I am glad you mentioned linear momentum as well as angular momentum as I can start with linear momentum. This is much easier but clearly points the way to go. A point to remember that will become important further down the line. Both linear momentum and angular momentum are vectors. Vectors have magnitude and direction. So to be conserved both magnitude and direction have to be conserved. Let us consider a fairly general system of particles which comprises our system for analysis. This may only be a single particle or it may be many, operating as a single unit. The centre of mass moves as if the whole mass of all the particles were concentrated at this point. The motion of this centre is completely independent of any internal forces (internal forces are those acting between the particles) since by Newton's third law every such action is countered by an equal and opposite reaction. If M is the total mass of the system and FE the external forces then by Newton's second Law [math]\sum {{F_E}} = M\ddot \bar \alpha = M\frac{{d\bar v}}{{dt}}[/math] I note that there is already confusion between you and Mordred on the meaning of the symbol r, which is why I asked you to define your symbols before. By convention r is used for a position or displacement vector, not radius. In either event I have used the greek letter alpha to avoid confusion. In any case we can quickly move away from this variable. The equation states Newton's second Law that the sum or resultant of the forces equals the total mass times the acceleration, where the acceleration is the second time derivative of the position vector alpha. This is shown by the double dots over the symbol. The symbol also has a bar over it to show it refers to the centre of mass position. OK That was a big chunk, now for the cool bit. In the case where the vector component of the forces in a particular direction is zero [math]M\ddot \bar x = M\frac{{{d^2}\bar x}}{{d{t^2}}} = 0[/math] I have taken the x axis to be in this direction so moved away from alpha as promised. This is a very simple high school differential equation which when integrated (solved) has the solution [math]M\dot \bar x = M\frac{{d\bar x}}{{dt}} = M\bar v = {\rm{a}}\;{\rm{Constant}}[/math] and [math]\bar v[/math] is the component of the velocity of the centre of mass in the x direction. This is hugely significant because Mv is the component of the linear momentum of the system in the x direction and it is constant. Constant means it does not change and we have fixed the x direction. So this is a form of conservation for linear momentum. But it only works because a term in our equation of motion is zero or null. It is not true in general. This type of 'conservation' is called a null based conservation. [math]{{\rm{p}}_x} = M\dot \bar x = {\rm{a}}{\kern 1pt} \;{\rm{Constant}}[/math] Where Px is the linear momentum in the x direction. That is enough for now, but I can tell you that conservation of angular momentum is similarly based but the derivation is more complicated as there is another term in the equation of rotational motion to consider. How are we doing?

First I would like to nominate this post as a shining example of the right way to introduce some scientific news or announcement for discussion. It contains not only the announcement but a short synopsis or summary of the material of sufficient quality to gauge the nature of the news. This is then followed by a link to a much longer original source material for those who want it. +1 As to the news itself. It is still early stages of an investigation, too early to believe or disbelieve the conclusions offered. I see there is, as yet, no independent verification of the alleged sapiens bone fragments, either in dating or being from Homo sapiens. I therefore look forward to reports from this next stage investigative stage. Too large a conclusion is drawn from previous knowledge that cartain types of stone tools are found widely distributed in Africa, coupled with this find. Until the other sites with these tools are shown to have been inhabited by sapiens, this is evidence from a single instance so cannot be counted as evidence of widespread location of sapiens 'throughout the continent'. No does it rule this proposal out. It is simply not enough either way. An alternative springs immediately to mind. North Africa was much more hospitable in those days, much of this has been washed away in the sands of Osimandias. So it is conceivable that somewhere in North Africa the sapiens started and spread, perhaps both ways. What we are finding are the remnants of this with the middle parts destroyed by the ravages of time.

In which case can we please follow the rules of this forum in which the promoter either completely sets out his stall in the first post or defines his terms in subsequent answers to questions about that which is missing from the opening proposal. I have asked repeatedly adn without success for proper definitions of all terms employed, the scope of all equations used and a full and accurate description of at least one system conforming to the proposed analysis.

Thank you for replying at last. Yes you can incorporate the drive in the track/vehicle system, but that confines the vehicles to special tracks exactly as I said. You need special tracks not only to provide forward propulsion but also to prevent sideways movement and to guide the vehicle around curves and intersections. How would a crossroads work? An important point about wheels is that you automatically get traction from the frictional contact with the roadway or even (especially in the american case) off-roadway surface.

I still don't think the OP has appreciated it's a whole lot worse than that. Assuming for the moment that you have levitated your vehicle by some means. What are the ways of propelling it? Propellor/TurboFan Jet engine Rocket Engine Have you ever stood behind a hovercraft fan or saturn rocket exhaust or any other of these? There is a real issue with other such vehicles on the road, even in perfectly windfree conditions. And yes, as Halls of Ivy said How do you stop, manouver etc?

I thought I would try to track down the original quote and I ended up here, where I have to say there is a more wide ranging discusion. https://www.quora.com/What-did-Einstein-mean-when-he-said-Science-without-religion-is-lame-religion-without-science-is-blind-And-do-you-agree-with-him One particluar (short) response sums it up Please note the entire article is reproduced as well as detailed information on the history and circumstances surrounding it.

Why would I ask you? I'm sorry if my intent was unclear. I do think that not understanding this difference may underlie Mandlbaur's difficulties. You are welcome to explain if you like, particularly as he won't talk to me for some reason.

Yes, I'd add +1 to Kip as well. But I'd also add that Kip's agebra works mass concentrations, useful now that we know we are talking about a food recipe. You did post this in Inorganic Chemistry where a Chemist might be forgiven for thinking molar concentrations, and why not organic chemistry for food?

There is a subtle difference between angular momentum and moment of momentum. Do you know what it is? Hint it corresponds to the differnce between a couple and the moment of a force.

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.