DrP

Density is mass per volume - so it depends on how heavy the matter is over what space it occupies, so 2 things are important - 1)The molecular weight of the atoms making up the molecules in the substance. 2)How densely packed they are. Molecules exhibit several types of packing, like hexagonal close packing, cubic or body centered cubic - look up molecular packing. The closer the molecules pack together influences the density - for example, hexagonally close packed molecules give higher densities because they are more densely packed, although it doesn't always go that the most dense substances have hexagonal packing, Lead for example is cubic or body centered cubic but is a very high density because the atoms are of a high molecular weight.... if it packed hexagonally it would be even denser.

Thanks studiot... it's u and dv that you define not u and v as I said... thanks for correcting - I didn't have time to look it up.

Don't have time as I am at work and there are many better mathematicians than me here... but - define your terms u = .. and v = ... and sub them into the integration by parts equation.... which I can't remember off the top of my head (too many years ago). u = x and v = sin2x ?? then put into the standard equation for the solution of integration by parts and do the sums. I 'think' this is right... I am sure I someone else will let you know otherwise... Mr ajb, for example, is awesome at maths here.

When you fall off the edge of the roundabout you fly off at a tangent as discussed. As the roundabout rotates a further 90 degrees it now looks like you are just flying off of it radially outward from the centre, but you are not, you are just going in a straight line still on what was the tangent a quarter spin ago and your frame of reference has moved... maybe that is where the confusion lies for some people. I really don't want to get into it as it has all been said before, I am just trying to see why some are finding it very hard to visualise that their flying off seemingly straight out from the centre is actually them flying off at a tangent. I Hope this helps... if not then just ignore it. ;-) x

That 5L wont be 5L when it leaves the tank and gets to 1 bar though right? (As spyman has said) How many litres is it at 1 bar? What is the flow rate? Do the division. Hope that helps.

Rob - I don't think you have enough info to make that statement... it depends on why the disk is spinning... it was undefined. It could be driven at a constant speed with a motor or in the case of the roundabout it may have a pusher keeping it constant. Otherwise, of course it will slow (like the skater stretching out her arms), but that isn't really relevant your conversation is it? I mean, it's been going round in circles for 10 pages.

Less dampening of the motion with the harder materials. Think about it, with a plastic plate, more energy is absorbed into the plastic as heat rather than being transferred back into the rebound. The harder material doesn't deform like the plastic. I'm certain that you are overthinking the 'Gravitational field' stuff... of course it won't work at zero G... neither will a see saw, unless the people on it were to push up with their legs each bounce... (so you might actually get some oscillation at zero G due to the bouncing if the system was set in motion by an outside force to begin with). It really is just a see saw.

Yea, it's just a see saw with low loss of energy to friction. Just a quick thought on the observed 'perpetual' nature of the plate on marble over a knife scenario... could air currents help keep the thing going for longer? Wouldn't take much for the system that is finely balanced to get started or be kept going by the occasional movement of air, no?

To start a thread asking for tips or advice on a problem that starts a discussion and brings people into it, then say 'you have your answer now' and not actually share that answer with us is a bit annoying... when asked politely what the answer was, so that people that were involved with the discussion or who were following it can draw an end conclusion to the thread, you reply with what you did, I find a little rude. Just saying. I can only assume you were upset by someone in some other thread or something. Anyway - if you are leaving, then who cares I suppose. I was actually interested to find out what the problem was...

What was the problem? Has she calmed down? Did you give her beer to shut her up? Apparently I was given a bottle full of Guiness as baby when I wouldn't shut up... I slept for hours apparently. I would not advise this AT ALL.... I can take it as I am super hard, but modern babies might not be able to take a bottle of beer. ;-)

Using my maths skills I can 100% guarantee that all six number will be between 1 and 49. 8-)

I prefer the 'view new content' page anyway.

I'd try without the chopping for the reasons you already gave... had similar experience before.... the solvent should still rip through plant pretty easily, so chopping it up is probably not needed and will give you debris. gl.

I think I saw it on a documentary once that you tend to only remember the dreams you have just as you are waking... that's why they say that if you want to remember them you should write them down as soon as you realise that you are awake and have just had a dream. I tend to remember the more lucid, reccuring ones. ones.

'Redshirts' by John Scalzi. I don't often post here, but this one is recommended for any Sci Fi fan... particularly if you are a Star Trek nerd. It is very funny. Certain crew members of the Starship Intrepid work out the unexplainable high mortality rate of new crew members when on away team missions. Eventually they figure out that they are part of a TV show chronicling the adventures of the 5 main crew members of the Starship Intrepid. The stars of the show never die... but if you are new to the crew and end up on an away mission with one of the main characters then you can expect not return. They plan a daring mission back through time to speak to the writers of the show in an attempt not to get killed off.

Fluff. Belly button fluff in particular is beyond scientific explanation! ;-) Where does it come from!? No one knows! ;-)

Actually, I think we are both right. lol One about the centripetal force and the other about the the force being related to distance to centre of mass. ;-)

If you stopped it spinning, assuming it doesn't 'pop' back into a sphere straight away, you would weigh less at the equator than at the poles due to your distance from the centre of mass/gravity of the earth, no? Therefore it is not redundant at all. Unless I am completely misunderstanding what you are saying again. ;-) Which Strange has already said above... sorry. We are going round in circles.. ;-) lol.

I hope whoever gets in will continue the good work (See post #83). Here we have free health care for who ever needs it regardless of whether they have any money or not. It works... really well. You guys need to embrace it. I've seen the propaganda videos that scaremonger the rich into not wanting to pay a tiny, tiny bit more tax so that everyone in the country is safe and healthy and cared for. They are mislead/misleading. Anyway - good luck America. I hope it all goes well - here's to positive progression! x

you should be alright for your first 100 wears of the product... anymore than that and it dissolves your brain. How many times have you applied it?

My fact about the distance to the centre of the earth at the equator compared to that of the poles was to put Tar on the right track after he was barking up the wrong tree. Things at the equator weigh more. How is that a non answer MigL? It isn't an answer at all, it was a reply to Tar getting things arse about face even though as Strange pointed out that swansonT has already covered all of this... hell, I wish I hadn't bothered. lol. Oh, and sorry if my comment about school was a little sarcastic. I know how you feel MigL. QUOTE, MigL: "I replied that, for the surface of rocks...." well, actually, you didn't, you replied as I quoted you.

The sol-gel reaction of something like TEOS goes from being a liquid with a suspension of growing solid particulates in it to being a solid gel at the 'gel point' of the reaction. This is the moment that the growing seed particles become large enough that they all interact and cross link and form a complete skeletal structure throughout the body of the medium. This yields a soft solid which gets firmer as the reaction proceeds.

QUOTE(MigL): "That's a non-answer DrP.......Why is it further from the centre of the earth.... Does the rock weigh less at the equator?" It is further from the centre because the earth is not a sphere - it is squished. I didn't think it necessary to explain that. So, yes, the rock weighs less at the equator than it does at the poles. Seriously? have you not covered that in school yet or something?

Tar - no, it weighs less due to there being less force acting on it by gravity as it is further from the centre of the earth.

It's not an infinite series because he doesn't keep stopping each time he reaches the last position of the tortoise... other wise it would be. His motion would be continuous and thus he catches the beast in the real world situation. That's how I see it anyway - please correct me if I am wrong, but I don't think I am.