studiot

With that list, this book should definitely be on your shelf. http://eu.wiley.com/WileyCDA/WileyTitle/productCd-3527406999.html

+1, good question swans. If your target is hard ( and brittle) then the speartip will be supplying energy to newly created fracture surface in order to penetrate. No large fracture force is required just a continuous supply of energy, so maximum impact kinetic energy is required. If your target is soft, as I suspect, then the target material reflows around the speartip and no fracture surface is created. In this case driving the spear in is more like piledriving or nail driving and the maximum driving force is required. This, of course, means maximum impact momentum.

Let's keep this in perspective. Resnick and Halliday, despite its title struggles as a first year university textbook in Physics. It would barely have got me through the A levels I took fifty years ago. It is aimed at students of technical disciplines such as Engineering, Chemistry and the like who need a basic background in Physics to supplement their main subject. So practice in Physics questions really depends upon what you want to do with your R&H background. The best way to find worked problems is to narrow down the subject area and look for texts in those areas. At tertiary level subjects texts tend to cover a narrower aspect than high schooltexts. For example electrical engineering, fluid mechanics, dynamics, heat, materials science, and so on all offer many excellent example calculation books Second hand texts can be had for pence. So help us to help you by identifying your particular areas of interest.

To the best of our knowledge, yes.

There is no evidence of significant mass change for the Earth since the original accretion phase in the history of the solar system 4 billion+ years ago. This accretion phase cleared most of the available material in our vicinity so we only get the odd wanderer or loose the odd atmospheric molecule nowadays. . Edit, Note the dinosaurs died out about 60 million years ago, a mere eyeblink in relation to the Earth's age. Also this was not the biggest mass extinction event, which occurred nearly 200 million years before the dinosaurs

Hello Kelly, It would be useful to tell us more about the effects you wish to create. Water itself will act as a paint thinner. When you say water colour do you mean water colour or are you including what used to be called poster colour (powder paint you mix up with water) ? What sort of quantity are you thinking of? An addition of colourless alcohol or glycol would change the viscoscity of the water (which is already low) and have the advantage of evaporating along with the water. I assume you don't want to add sticky substances like gels to the mix. The change is complicated and depends upon the concentration, but the viscosity will be higher than either individual liquid. I remember an artist who created the most dramatic effects about 50 years ago by curdling indian ink with a small amount of water. I will try to look out a photo of the effects, but this will take me a couple of weeks. Another thing to consider is surface tension. This is likely to be more significant in thin films, such as used by artists. The surface tension is reduced by adding a colourless detergent, such as used in chemical laboratories for cleaning glassware. This does not leave a residue on the glass so is ideal for your application.

I thought swansont might say that, but in fluids there are two methods of analysis, relative to the flow and relative to a fixed reference. The velocity is constant, relative to the flowlines. But this is a boring non productive argument. capiert this might help if you can follow it. http://www.efm.leeds.ac.uk/CIVE/FluidsLevel1/Unit03/T5.html

It would be generous and helpful if we could all dispense with comments like the underlined henceforth. In brief answer to the rest of your post: When a fluid, travelling at constant fluid velocity, passes round a bend or elbow in a pipe, the pipe exerts force on the fluid to turn it around the bend. In turn the fluid exerts a reaction force on the pipeline. This force can be considerable, enough to blow the joints or burst the line (as I have seen). Or the line may simply be displaced. It is this force that causes a hosepipe to snake about. This force is there even without friction. If we add friction into the theory the fluid will exert a bursting force on every flange and coupling joint, even in a straight pipline. Does this help

I beg to differ, this statement is ambiguous at best and can be misleading. I have personal experience of disasters that occur when engineers fail to appreciate the need for proper thrust blocks in pipelines. Please can we just collectively establish what capiert is trying to present and move forward?

I agree this is a static electricity effect. +1

No your question is neither silly nor simple, but I hesitate to answer for safety reasons without considerably more information. First and foremost Why do you think the liquid (?) is acid? Is there a label? (it could always be mislabelled) Some people keep other corrosive liquids in bottles, such as bleach or caustic soda. Secondly what do you want to do with the stuff? Now for some data specific quesions What colour is the liquid? Does it have a smell (care needed here in testing)? It can't be hydroflouric acid if it is in a glass bottle. How big is the bottle? Can you post a photo? You say it is in the garage. It could be drain cleaner, rust remover, concrete cleaner (all of which could be pinkish phosphoric acid) battery acid. Over to you.

+1 for providing a model or example format when querying someone's post. The one thing I did not mean to imply is that a flux of photons constitutes a wave. Remember that this thread concerns the wave theory of light so my response was in those terms. The wave theory regards light as two connected fields, an electric one and a magnetic one. It does not address specific corspuscular properties also possessed by light, that are best described in terms of corpuscles (photons). The idea behind my phraseology is that a lightwave comprises a series of periodically varying electric fields, which generate varying magnetic fields, which generate vary electric fields as the lightwave moves along. These fields do not exist at a particular point, before the lightwave arrives there and cease to exist there after the lightwave has passed. It is in that sense that the lightwave carries its own medium, the fields are the 'medium'. Does this help?

Capiert, to save further argument over terminology I suggest you research Momentum Transport This is the technical term I think you are trying to portray. There is a whole branch of engineering science about this https://en.wikipedia.org/wiki/Transport_phenomena

Funny I thought I said in my post

The big difference between light and all other waves is that all other waves require a real external medium to propagate in. Light waves carry their own medium with them or alternatively create the 'medium' as they go along. This means that for other waves there is a real something to push against that is not the wave itself. In the case of sound this something is the air. So another agent that can push against the air can push the air molecules in exactly the right way to counter the wave. For light there is no 'third party' involved in the interference and, as Strange notes, it is very very difficult to create another light wave of exactly the right frequency and phase to counter a given one. Until the advent of lasers this could only be done by using the original light ray itself By splitting it into two parts and changing the phase of one part and then recombining the two parts destructive interference can be caused. This is used in engineering to measure small thicknesses of transparent things like glass and oil or chemical films / coatings etc.

You need to study Eutectic mixtures. https://en.wikipedia.org/wiki/Eutectic_system

Have you loaded the Radeon drivers? Look in the bios and see if you can transfer control to the onboard graphics, if there is one and use that. The output may have a cap over it as Dell have also fitted a higher graphics card. It may also be that when you removed the old card control transferred automatically to the onboard graphics. Edit oops I missed one of phi's darn commas.

Felicitations Monsieur!

I will start from the beginning, because the answer is not simple. Something feels hot to touch because heat is transferred from it to the hand. Heat only flows from a higher temperature to a lower temperature. The greater the temperature difference, the greater the rate of heat transfer. Your sense of touch is mostly sensitive the the rate of heat transfer, not the absolute temperature difference. If you touch a plastic spoon and a metal one at the same higher temperature than your hand the metal one will feel warmer, because the rate of transfer is greater. The reason for this is because the heat in the spoons has two separate sections to its journey into your hand. Firstly some heat has to be transferred from the point of contact to your hand. This increases the hand temperature at the contact and depresses the spoon temperature there. Then heat has to be internally transferred within the spoon from the now hotter parts to the point of contact before more can be transferred to your hand. This happens quickly in a metal (or other conductor) spoon but slowly in a plastic (other insulator) one. The speed of replenishment is controlled by the thermal conductivity of the spoon material. Your garden spade is more complicated because the heat capacity (specific heat) of the wood is about 5 times that of iron (about 2.5 to 0.5 in metric units) so the iron blade will heat up to a higher temperature than the wood for a given solar input. So the wood starts off at a lower temperature than the iron and transfers heat more slowly. Both effects combine to make the wood appear (and be) cooler. Since you asked for the property which is smaller for iron I assume you are looking for the heat capacity. The conductivity of iron is much larger than that of wood.

I'd like a closer view, but try garnet if they are indeed crystalline. https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=garnet&gbv=2&oq=garnet&gs_l=heirloom-hp.3..0l10.1083.4067.0.4937.8.7.1.0.0.0.137.671.6j1.7.0....0...1ac.1.34.heirloom-hp..0.8.693.JKU-Tp15PTw https://en.wikipedia.org/wiki/Garnet Can you give us some more details about their location? You can pick this sort of mineral out of the side of the river South Esk gorge in Angus, Scotland.

Since this is the day for jokes. http://www.bbc.co.uk/news/business-36638929

Thanks, Mordred. The point is also that the book was in pure maths but contains some excellent wisdom and is a very good read, not just the extract I posted. It could be called the study of group theory via Scottish Dancing.

Thank you whoever read my last post for the support. For your information, in 1963 I saw a stage performance of Hamlet. The stage effects included a very realistic ghost behind a gossamer screen by edge projection lighting. Yesterday I saw the technique again at the permanent RSS Discovery exhibition in Dundee. Of course edge illumination has been used to illuminate characters in displays since the early days of radio.

I'm sure you know that I was not referring to improving changing or replacing a model in the light of new and better data. That is 'encapsulated' in the example I gave.

I see no one was interested in my Oxford model of a model, but don't you think this is a bit limiting? Another valid question might be paraphrased as If the model appears thus today was it the same yesterday and will it be the same tomorrow? Astrophysics is currently wrestling with this exact question.