studiot

Bhazee, thank you for the feedback. If you are studying stiffness matrices your are obviously a clever chap. The moral is if you want your questions answered don't make your respondents guess what you mean. go well

Two telling points about people who associate magic with constellations. 1) They don't realise that stars which form a pattern in our sky eg the famous W may be a long way different in distance and that the pattern is simply a projection on a spherical shell in our view. 2) The further don't realise that these patterns change over time so something that is aligned today would have offered a different relationship in the distant past. Here is a different experiment about patterns and alignment. Take a blank sheet of paper. Scatter some black pepper grains onto it. You will find if you take a ruler and check the slignment of these random dots that you can draw 'leylines' on your paper! Now stretch and distort that paper so that it wraps round a sphere. Are you 'leylines' still straight?

Done it. Thanks [math]A \varsubsetneq B[/math] {math]A \varsubsetneq B[/math} change the outer brackets back to square

The obvious conclusion is that both the corpusculer and wave models are inadequate by themselves and that the true nature is something with some of the characteristics of both plus perhaps properties we have yet to uncover. Why is this so hard to swallow?

One of the silliest things about this argument is that there is no need for a case of 'either....... or' as presented. I already asked is an aluminium salt an acid or base? Answer it is both. How about the bicarbonate ion in solution in the presence of HCl? Answer both at the same time.

And just how many times in the past have scientists and thinkers made this claim that they know everything? Mendelev and his mates were wrong about the number of elements Kelvin was wrong about the cooling of the earth.... I suggest that anyone making such an extravagant claim is suffering from a severe case of bloaty head.

[tex]\A subseteq B[/tex] So how do these work then please?

Well I had a go but couldn't find how to do it. I can certainly draw the symbols in MathType, but it won't create Tex from them, although it will create a pastable entry for Wiki and Google.

Actually, pmb, the distinction is worth making. One property of a field (from the mathematical definition not physics) that is useful (vital even) in physics is that the field is closed under addition. This is important if you wish to postulate a finite yet unbounded 3D universe. This is a good concise definition I couldn't quite remember before. Thanks

I'm sorry I'm still no nearer understanding your objective or subject. For the record I do not agree with Bignose that it is unimportant where the origin lies in relation to a control volume. Some physical properties can takeon positive and negative values, some can only be zero or positive. This has significance if you are considering such quantities over a control square or cube that is entirely in the first quadrant or symmetrically distributed about the origin.

bhazee doesn't seem bothered to come back or discuss so I am just posting this for the record. The original question was asked as an engineering question, but very scantily put. As an engineering question I also think it refers to matrix structural analysis by the stiffness method. When you assemble the overall stiffness matrix for the whole structure from the individual elemental stiffness matrices you can take advantage of the inherent symmetries to reduce the stiffness matrix and thus the computational work to triangular or banded form. I think this is what the OP is referring to.

Yes indeed and further the use of the word critical ( and criticism) needs comment for it is used here in its formal sense. As such you must start with something to criticise!

Which is why I suggested to stop arguing at cross purposes.

26...........-2 28...........-1 31...........-2 35...........-1 71...........-1 7 or 5 ? C'mon folks we are adult scientists here, not politicians. We should all be able to see through the "How many sheep in a field argument", which runs Look in the field how many sheep do you see? Three What if I tell you one is a lamb?

Addendum to pmb's description. A field need not extend to all space, just some region of space. However there must be a scalar or vector assigned to each and every point in that region. The region need not have the same number of dimensions as the space. So in 3D space the region may be only 2D ie a surface. This is very common. For instance the surface of a shell or sphere is often used.

Actual it makes more sense for our ancestors to have done the moving since they were likely under the influence of Druid Special Brew, whereas it is well known that superbeings are unaffected by alcohol.

Hello qft, I see you are interested in chemistry as well as physics. I don't know why wave/particle duality evokes such strong feelings and reactions. We do not find it suprising and readily accept schizophrenic behaviour in other physical phenomena. The short answer is that the behaviour depends upon the circumstances ie what we do to the subject or what we want from it. As a for instance or two Aluminium compounds are often amphoteric depending upon whether their environment is more acid or more basic. I have a piece of black plastic on the end of my DVD controller that I can regard as opaque if I look at it (visible light) or transparent (infra red) from the point of view of the internal transmitter. So it is with quantum theory. If we look for particulate effects, we will find them eg the photoelectric effect. If we look for wave effects we can find those too eg diffraction.

I wonder if anyone sang anything at Wolford Cchapel near me.

Well I'm even more confused now. I didn't apply a control volume to anything. I didn't want to introduce anything irrelevent so I deliberately kept my discussion short. If vectors or control volumes prove inappropriate I was not going to discuss them further. For the record I actually said And you didn't answer my question Edit : I see that my question could have been taken to apply to your comments. It wasn't. I was asking if you could explain the OP to me.

I don't know. The one that has been moulding on my wall for the past 50 years has fostered many lifeforms.

49.216 * 1/0.9988 = 49.23 So they are correct if they used 1.000 kg/L

specific gravity definition sg (ethyl alcohol) = Density EA / Density of water at same temp. Density EA = 0.9988 * 0.7893 kg/L = 0.9988 * 0.7893 * 2.2046226 lbs/L = 0.9988 * 0.7893 * 2.2046226 / 0.035314 lbs/cuft = 49.216189 lbs/cuft I note you have water density as 0.9988 in one place and 0.9982 in another in your post go well in your exam.

Yes you are right there is overlap between the isobutane and the pentane. However you are given two pieces of additional information which allows you to form two simultaneous equations in 2 unknowns. I have attached a start, can you take it from there?

The best ones don't. I refer you to the Cambridge University Book On Space and Time edited by S. Majid It includes essays by John Polkinghorne, particle physicist and anglican thologian Michael Heller Professor of Philosophy at the Pontifical Academy and some who are scientists pure and simple. They get along just fine.

Try Dynamics and Relativity : W. D. McComb : Oxford University Press An integrated treatment of classical mechanics and special relativity The Manchester Physics series has some good volumes. Elementary Fluid Dynamics : D J Acheson : Oxford Is first class