studiot

I didn't know this and I find it an overgeneralisation that is prone to my outsmarting by Nature proposition. We are moving somewhat off topic, but every time I try to open up my own thread for discussion of these topics the pack of baying hounds here drowns out serious discussion. Any way I should have said the basic dimensions of Mechanics, not Physics or Science as there are more. Here is an interesting tabulation of dimensions for properties, qualities or quantities in Mechanics, taken from an old Fluid Mechanics book because they are arranged in an interesting way. Note they are based on Length, Time and Mass Such a classification is incredibly useful in Science. But it does not tell the whole story. Some of these have (need) a start point and an end point for a measurement. Length and time are are of this nature. This is because there is no absolute system of length and time. Some need no start/end points. Mass is one of these. There is either x amount of mass or there is no mass. But note this has nothing to do with the units we measure in. We use units so that we can compare one length/time/mass with another. However this is where Nature starts to play tricks. Some units have a foot in both camps. So the volt is the unit for both (electric) potential and potential difference and both have (different) meanings. Temperature is different again since, unlike mass, there is an absolute scale constructible. Then again variables are classified as extensive (eg mass) or intensive. (eg temperature) It is often said that extensive variables depend upon mass but that is not always true. The point of all this is that length and time are intimately connected and many subsidiary variables can be formed using only these two. It is difficult to find many variables with only mass and one other (see my table)

I realise that, I just don't know what more you guys wanted?

Since this is schoolwork it should be in that section (ie homework). As such have you tried following John Cuthber's lead by googling water repellent carboxylic acid? https://www.google.co.uk/search?q=water+repellent+carboxylic+acid%3F&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=UJ2zWtL3HZGLtgeRlYaYCA

TinTin +1

What questions? I am fond of saying that despite our best efforts to categorise and pigeonhole things, we are often outsmarted by the diversity of Nature.

Have you been reading Eddington's "Space Time and Gravitation" ? A very readable account of relativity, old but still good. I'm not sure what was unclear about my comment, but since two members have asked would someone like to tell me? Take measuement of length. What do you mean by length? It is the difference in 'distance' between two distinct points. But points in what ? Take your galaxy that is no longer there when you arrive. What is the 'distance to it' ? Distance has meaning unless you measure both endpoints at the same time. This is of no consequence over the length of a 1 metre ruler, but for the travelling twin to Alpha Centauri it is a significant question as I asked in that recent thread. So time is intimately involved with emasurement of distance. So how do we measure time? Well take the travelling twin again. He measures it by difference between the reading on his clock when he starts and when he arrives. Or the delightful story of his cigar in Eddinton's book. But, of course, he has to know when he has arrived. For which he has to know the distance he has travelled and how does he do that? But mass and temperature are fundamental physical quantities that we do not (need to) measure by difference.

Thank you for that link, I enjoyed the one about the delta flood barrier. Made me quite envious of the engineering.

I note you said time interval, which is good. Time itself is never measured. All measurements of time are measurements of time difference. In space, of course, all measurements of 'length' are also measurements of difference. This reflects the fact that there is no such thing as absolute time or absolute difference. However if we consider the third fundamental dimension of Physics - mass measurements are not of mass difference, they are of mass itself.

Well it was an Italian professor who invented 'The graphical calculus' - graphical here means geometrical. Graphical integration is easy peasy. In fact using geometry to perform calculations of all types used to be routine in a drawing office, but has gone out of fashion these days. It's all to easy to find a 'super thingy calculator' 'on the web. The trouble is if you don't understand it - I wonder if that happened with the recent Florida bridge failure. Anyway I though you might be interested in a practical hands on approcach. That is why I recommended Middlemiss.

Mathematics already has several alternative approaches to 'euclidian' geometry' as well as extensions to it. So what would yours offer and how would you propose to get education authorities to put it on their curriculum, as schoolboys tend to learn only that which will help them pass their exam, and sometiems not even all of that. Edit I see you missed my post by 1 minute before leaving. Here are a couple of references you might find useful. E.A. Maxwell The School Mathematics project Geometry by transformation Cambridge University Press R.R. Middlemiss Analytic Geometry McGraw-Hill

Of course repeat tests are good; tests of variation of parameters are even better. Note well that many carcinogenic substances are cumulative. That is the body does not excrete them, so as Tesco says Every Little Helps.

The fundamental devices (klystrons and/or magnetrons) in radar are resonant devices.

Why does this matter, it is for an English class? Is radar a weapon?

Read your Bible (hint Joshua)

Have you ever tasted beer in a glass that has not been properly rinsed in the pub?

Good point, often forgotten +1 Be advised the OP hasn't visited since January.

BBC article about a series of articles published today in Science about finds in Kenya spanning a million years of human development and evolution, including links to historic climate and other conditions changes. http://www.bbc.co.uk/news/science-environment-43401157

Yes, the BBC has produced some excellent Earth Science programmes and also issued them on DVD. https://www.amazon.co.uk/Earth-Story-DVD-Danielle-Peck/dp/B000FS9SGE Also good The power of the planet series https://en.wikipedia.org/wiki/Earth:_The_Power_of_the_Planet

Why do the bean counters of this world always insist on killing the golden goose? Geothermal can be overdone or it can be wonderful. I understand that in certain parts of Sweden (where they did a lot of it) ground source heat pumps are now banned as they created ground permafrost. Some civil engineering techniques depend upon ground freezing, which use basically huge GS heat pumps.

Good morning, datlemondoe and welcome to SF. The second order integrated rate law is only as you state if the concentration of A is equal to that of B, otherwise it is more complicated as follows. If [math]\left[ A \right] = \left[ B \right][/math] Then [math]rate = - \frac{{d{{\left[ A \right]}_t}}}{{dt}} = k\left[ A \right]\left[ B \right][/math] But since [math]\left[ A \right] = \left[ B \right][/math] we have [math]rate = - \frac{{d{{\left[ A \right]}_t}}}{{dt}} = k{\left[ A \right]_t}^2[/math] On integration [math]\frac{1}{{{{\left[ A \right]}_t}}} = {\frac{1}{{\left[ A \right]}}_0} + kt[/math] Which is the expression you have. However if [math]\left[ A \right] \ne \left[ B \right][/math] Then [math]rate = - \frac{{d{{\left[ A \right]}_t}}}{{dt}} = k\left[ A \right]\left[ B \right][/math] We cannot replace the and the integration is more difficult. The result is [math]kt = \frac{1}{{{{\left[ A \right]}_0} - {{\left[ B \right]}_0}}}\ln \frac{{{{\left[ A \right]}_t}{{\left[ B \right]}_0}}}{{{{\left[ A \right]}_0}{{\left[ A \right]}_t}}}[/math] But k remains the same constant. Does this help?

there is no need to look elsewhere, though of course you might find a better idea. We have an engineering section here and this is a building problem, not a chemistry one. But never mind, that won't stop us answering. But how about the building details I asked for? in particular is the floor anything like this? There will be a thin layer of fine concrete above this called a screed, to form the surface of the floor for finishings - carpet / vinolay or whatever.

Hello Simon, I think we need more details. I can't see the Ytube it says private video. Why have you asked this in inorganic chemistry? Concrete is more engineering surely? Anyway details of this floor and the concrete would be appropriate. You call it a floor and say it has a void beneath it so what is above it? What is it the floor of? There is a form of construction which uses inverted T beams spaced one lightweight concrete apart. The lightweight blocks are placed on the heads of the inverted T, spanning between the beams and form a highly insulating floor. Some types of lightweight aggregate and some cements are made from partly burned clinker and power station ash (Fly Ash). There might be a particularly poorly burned piece in one block which has somehow been reignited, if you have this type of floor construction.

Uncertainty manifests itself in many ways, the exact details varying with the circumstances. Rather than argue over uses of FT, here is a clear cut classical example of uncertainty which also clearly demonstrates the difference between errors and uncertainty. A concrete beam spans between two walls and carrier further structure above it. Strength and deflection calculations involve the self weight of the beam, the exact span distance, the further loads imposed by the structure and so on. None of these are certain and modern practice uses what is known as partial safety factors to accomodate these variations or uncertainties. However it is also possible to make errors either in the measurements or the calculations which assume perfection in that respect.

I didn't say it was, I said FT s are used in classical Physics. Your point I was indicating is that uncertainty is inherent in the maths, not the measurement. It is there whether a measurement is made or not. Please note I edited my previous post whilst you were posting yours.

Good morning, Shauno. thank you for your reply. Please read swansont's reply above. Fourier transforms, for instance, are used classically. I think it is important to note that there is a difference between errors and uncertainty. Uncertainty is inherent in the mathematics and cannot be avoided. Errors are more tractable by various operational and mathematical means. Number (of moles) is one of the fundamental quantities and is a good example of something that is inherently certain, but still prone to the possibility of error. The next bit is not off topic because it is linked to uncertainty. I don't see how this relates to the full text of the comment in my post and the mathematical procedure was referring to.