studiot

Well from what I can see, you gave fuzzwood the correct formulae for energy, but you are having trouble understanding acceleration. For this reason you should complete (1) first since it is easier, and properly answer my three questions about it. As regards question (2) Do you think this is an energy question? Do you know the formulae (equations of motion) for a body with zero acceleration and constant acceleration?

In physics (and other sciences) every word is important and means something or it would not be there. I'm sorry you have to translate from your native Romanian to English but we must try. So we cannot guess the problem you must tell us all of it.

One step at a time. You say the 1kg mass is travelling vertically upward at a speed of 10m/s. So is it accelerating or decelerating or is the speed constant? Please tell me why (or why not) in each instance.

You are asked about a single state and is for a change from one state to another. The only available change is from/to solid and liquid and for an equilibrium state Gsolid = Gliquid so =0 always. The diagram I drew is followed by most substances, and results in my truth table. It is true that water is anomalous and line B leans back for water so your Tsystem may be < Tt ; thus making D may be correct for water. However it still goes upwards (on the P axis) from Tt so Psystem > Pt always, even for water. But you were asked which was always correct and D is only correct sometimes, but incorrect most times. It was nice to see someone thinking about it.

So what have you achieved so far, and have you read the rules of homework help? http://www.scienceforums.net/topic/75772-read-this-before-posting-in-homework-help/ Don't forget to convert temperatures to absolute before doing any calculations.

Since you have the answer and seek deeper explanation for it I think offer a fuller discussion than would be allowed initially for homework. The question discusses G so I am guessing this is a Chemistry question. Chemists and physicists use P as the vertical axis and T as the horizontal axis in a PT diagram, unlike engineers who tend to do it the other way round. You say that you are interested in nanotechnology so I assume that includes computing and have constructed a truth table. Now the question is about understanding two things and has presented two statements about the state of the system. This is because it is about two separate things, the phase rules and the general form of a PT diagram. Firstly the phase rule, from which we can deduce that for equilibrium across a phase boundary G1=G2 ; P1=P2 ; T1=T2 where 1 and 2 refer to the phases. The equilibrium is important because even if the question did not explicitly state this you need to assume this and not that the system point is just passing through the liquid/solid phase line. If it is just passing through and not in equilibrium we cannot apply most of the equations and cannot even determine the 'state' of the system. OK so the system state is in equilibrium on the solid liquid phase boundary. You say you understand why [math]\Delta G = 0[/math] so making the [math]\Delta G[/math] statement in A, C and D true. Do you also understand why the [math]\Delta G \ne 0[/math] statements in B and E are false? The second statement made in the question concerns the systems state pressure/temperature relative to the triple point pressure/temperature. I have drawn a PT general diagram but this is where you need to do some work, to become familiar with the characteristics of these diagrams. The triple point is marked TRP on my diagram but I have not identified the lines, although I have divided the diagram into regions where the pressure/temperature is greater or less than the triple point temperature/pressure. Can you identify the solid. liquid and gas regions on the diagram. As a result on which line does the system state position lie A, B or C? Once you have the answers to the above you should be able to check off all the truth/falsity values in the last column of my truth table. You answer is then the only one with True in both columns.

Hello colemanwk, and welcome. Ophiolite has given good advice, +1, you should be able to discuss this with your professor, I'm sure he will be happy to expand on his title. Yes I agree that the English is unclear for a number of reasons. But then you have not told us the context of the Question. That is in what subject, module or course is it set? This is very important because of the wording. Firstly you have stated methods in the plural. So I wonder if this is about the so called scientific method, or even any particular method since the meat of the question is about the impact not necessarily the method itself. So for instance if this essay is for social history or ethics what about the ethics of the scientific methods employed by tha Nazis or Stalinist Russia? Or perhaps you wish to go much further back in history. The ancient Greeks were great scientists, but poor technologists and never built arches or great aqueducts for instance. By contrast the Romans were poor scientists but great technologists, who applied the scientific knowledge of the Greeks. Or perhaps you could discuss the change from religous based 'science' to observation based science in the renaissance. Names like Galileo and Copernicus come to mind. One final thougt, Cambridge University pioneered the term 'Natural Sciences' by which they mean the physical sciences. https://www.google.co.uk/search?hl=en-GB&source=hp&q=cambridge+natural+science+tripos&gbv=2&oq=cambridge+natural+science+tripos&gs_l=heirloom-hp.3..0j0i22i30l4.5109.18844.0.19344.32.19.0.13.13.0.219.2498.1j16j2.19.0....0...1ac.1.34.heirloom-hp..0.32.2981.tJ79Z5X69Dg So you should clarify this with your professor. He may mean what is termed the 'life sciences'.

Thank you phi for all, I was hoping a moderator would intervene. +1 (post315)

No, If I had meant you I would have said so, although some of your remarks do not suggest even handedness to me. Are you suggesting that iNow did not put up post#281 or that he has no responsibility for its content or if neither, what are you suggesting?

How much maths do you know? OK so add 0.024 x 109 cubic kilometers to 1.33 x 109 cubic kilometers and rework the figures. How much difference does that make?

I have no idea who or what Randall Munroe might be. I had understood that posters should not ask others to read links except as further information and that they posters should verify for themselves the worth of any link they offered. I further thought posters should refrain form personalising and adding emotively loaded sarcastic comments to their statements, which might otherwise be truthful. As regards to your comment on the thermal expansion of water I have presented my calculations for all to see.

I don't usually award minus points but I did so this time for deleting something offensive after I had answered and referenced it in my post#303. Have you done any calculations on your supporting links to test their veracity, I am currently looking at the expansion aspect. Do you have any data for how deep the expected temperature rise would penetrate in 200 years and does that data discuss where the energy would come from to raise the water temperature nearly 10 degrees centigrade and how long it would take to perform this feat in a kettle the size of the world ocean? Edit : OK so here are some more calculations Taking the figure of 1.33x109 cubic kilometres of water from post#282 and the coefficient of cubical expansion of water, which can be found in any decent book of engineering tables as 0.000214 or here http://www.engineeringtoolbox.com/volumetric-temperature-expansion-d_315.html I calculate as follows For a rise of the whole ocean of 10 degress centrigrade the expansion is 1.33 x 109 x 0.000214 x 10 = 2.85 x 106 cubic kilometers. This figure is about 10% of the volume of ice available (again detailed in post#282) at 24 x 106 cubic kilometers. This does not agree with your statement in post #302

Do you not agree that figures should be accurate or that sources should be checked for veracity before being presented as fact?

I have already referred you to post#281, byiNow, where the figure 200m is writ large. Who do I report these unseemly attacks to, since they now appear to be personal?

Well correct me then. Prove your claim. I was not attacked like this when, earlier in this thread I corrected a statement by Tim, although I did not join in the hounds baying at his heels in what seems to me to be a witchhunt.

How many million years ago was the cretaceous? So you have an accurate topographical/barymetric map of that time? You are a scientist so how can you compare data from millions of years ago with an event predicted to happen within 200 years? How can you be so certain that the topography will change so that such a rise is possible? If the topography does not change where will water equivalent to double the total ice come from, to bring this rise about?

I find this very disappointing and the rest of your post rather biased, especially considering this statement I made immediately after post#281 What about it? What about the quantity of ice that is floating above the current float line? There are probably quite a few factors that will affect the final figure in either direction, a small amount. I am supporting neither side in this discussion. Unfortunately climate change arguments always seem to end in tears. But I do like to see facts accurately represented. Perhaps, but if that is the case why did the originator not say so? I have seen him or her online her since that statement was made.

No I don't think you did, but I am fed up with verbal fencing for the sake of pointless argument.

Yes indeed that is true. But overall machine efficiency (and therefore fuel economy) is measured in terms of heat or work out against the calorific value of the fuel, not in terms of how well the fuel burns. What do you think of my distinction between a boiler and an internal combustion engine? One produces heat, the other work. Not only this but the IC engine has a large speed variation, so time available for fuel distribution varies with speed. Is the proposed method using sound capable of accomodating this? So I am querying whether it would be more appropriate to consider this for boilers. Yes comments from a mechanical engineer would be welcome, by why restrict to auto and? why not also turbines, gas engines, oil engines etc? It may be of interest to note that before loudpeakers were invented there was a device called the ionophone that performed the reverse operation. https://www.google.co.uk/search?hl=en-GB&source=hp&q=ionophone&gbv=2&oq=ionophone&gs_l=heirloom-hp.3..0j0i10l9.1562.4343.0.5812.9.9.0.0.0.0.140.1048.1j8.9.0....0...1ac.1.34.heirloom-hp..0.9.1048.DaYQEsg3jH8

Yes you said you wanted it to spread out, but why do you think that will increase the explosion? And even if it does why do you think that will help an engine that depends upon the expansion of gas? The smaller the start volume the bigger the final expnasion and the more the work that can be extracted. This is the reverse situation from heating a working fluid in a boiler or heat exchanger.

Airbrush, now your rocking! +1

Welcome soil engineer I look forward to some interesting posts. As regards combustion, why would you want to spread out the fuel? Boiler Plant that burn fuel would certainly benefit as the heat of controlled combustion is transferred in the heat exchanger. But combustion engines need to burn the fuel as quickly as possible since the wanted energy transfer is not thermal but mechanical in the work done by the expanding gases. Thus concentration is required. Timing also plays a part.

Do sensationalist replies help? Let us look at the figures. (Well spotted Greg H, yes obviously the units of volume are in cubic kilometres. But the numbers were correct.) Arete your reference has much the same figures as those from the US geological Survey official figures http://water.usgs.gov/edu/watercycleice.html But theirs have some additional material that is worth studying. So let us tabulate Total Water volume 1.33 x 109 cubic kilometres Total ice volume 24 x 106 cubic kilometres Current water surface area 361 x 106 square kilometres Curent average depth 3.68 km So if all the ice melts and the area does not increase that corresponds to an additional depth of water of (24 x 106) / (361 x 106) = .066km = 66m, say 60 m to allow for the spread as the depth increases. We can also expect a hotter earth to push more water into the atmosphere, reducing this still further. So what is the source of your figuring, iNow? don't you think 200m is excessive?

You could claim the same about being unable to discover what happens in the sky, without leaving the planet's surface. But it has probably been known since prehistoric times that clouds cast shadows. You could say the same about what happens in nearby space without leaving the planet. Again eclipses and other occlusions have been observed since antiquity. You could say the same about outer space without leaving the solar system. But what about the prediction and subsequent discovery of Le Verrier's Planet? So I could continue to extend outwards, you get the drift.

The rate of chemical reactions increases with temperature increase. So processes which involve chemical weathering will speed up. If you are interested the effect is called the Arrhenius equation. http://en.wikipedia.org/wiki/Arrhenius_equation