imatfaal

I worry that we are all too specialised for our own good and that the fraction of the population [creep]even such an erudite and well informed group as SFN[/creep] able to make a meaningful contribution to any hardcore scientific discussion is vanishingly small outside those already contributing to the debate. I think your idea is magnificent but unworkable, it would end up with the few experts in any particular area spending too much time explaining what they consider basics; ie any paper that is general enough to be understandable by the layperson will be too mundane for the cognicenti. I would love to see the return of the age of the "amateur scientist" making real contributions - and what better discussion medium than SFN - but I feel those days are well and truly past. I hope I am wrong and this becomes a staple for SFN

TwinB - I was interested to see the results of your poll, and not a little surprised when I did; I will say no more to avoid prejudicing others. I think the more interesting question is "Why do so many people feel the need to believe in ghosts?" Is there a deep need within the psyche that causes a majority of most populations to believe in supernatural phenomena? We replace thunder gods with an abrahamic god, which we subsequently replace with healing crystals; why do we, as a species, need a supernatural crutch? Hal - are you just trolling cos you are way off base

"pointing" at least in the UK, can leave a nice smooth arc in the mortar - which is what your tool would leave. Pointing normally creates a little tip in the mortar so that a drip forms and fall off, but there are forms that would work with your tool. Your tool could well be for making an semi-circular depression - often called "handling" or brush-handling" (cos you can use the handle of a paint brush). But as Michel said - there is no way this would be plated brass, unlikely even to be brass.

the problem with the indeterminacy of translation is that examples of mountains being called "your finger" or "what's that" are amusing but limited; yet examples of cross cultural dissemination of learning are everywhere. you referred in another thread (in another great post) to Wittgenstein On Certainty - and whilst "here is my hand" may be interpreted in any manner, and is suspect when claimed to be an unarguable empirical fact, as the commencing logical proposition of a series of arguments it is completely acceptable. Similarly, whilst it is completely credible that no translation (or we could go further and say no speech act) is interpretable with complete precision and without bias from one's own interpretive community; it is nonetheless logically valid to assume a measure of mutual understanding will be possible

So now we agree that your table is basically a list of numbers generated by an arithmetic series (ie it is .102... multiplied by any +ve integer) , would you also agree that it can have no predictive power because any/all masses can be "predicted" with an "error" orders of magnitude smaller than the experimental error. If you bet on all the horses you are bound to win! I like the fact that you are willing to formulate ideas and put them up for scrutiny and I hope you understand that I am not being deliberately obstructive rather I am pointing out those errors that occur to me. That said, I think you are wrong; the quest for a classical explanation is doomed, but the actual journey to that realisation may prove very illuminating.

As we have no benchmark to compare with this is speculation, but I consider Humanity as a race as very adaptable. Every day at work I do things without thinking that when my father was my age he would would have been considered extraordinary, my grandfather would have considered amazing and previous generations would see as pure magic. What requires a huge paradigm shift for the individual is merely a tiny increment for the population en mass. And it isn't just technological progress - again anecdotally, when my father moved down to London many boarding houses openly said "no coloureds no irish" (he was told that as a geordie he was as bad as the irish by one landlord) ; now whilst there are still pockets of clandestine racism in the UK this form of open hostility is unthinkable. We adapt, we change; what was unthinkable becomes the norm and it is difficult to remember that we have become so different so quickly.

The more I look at this question the more I like it - the two sections use two different ways of looking at energy conservation yet both resolve to an equation that is easily recognizable as equivalent to a simple equation of motion. the condition of using energy struck me as picky - but I realise I was missing the point of the q.

PhDW - great links/post.

Intriguing - please do let us know if you get anywhere. I wouldn't know where to start - but what about this sort of place http://www.papawswrench.com/vboard/index.php its an antique tool forum. [guesswork] some form of smoothing tool? I could imagine using it to create a smooth semi-circular depression; I would use my finger - the smoothing action of the pad of the finger would be simulated by using the rounder side (ie third picture) and the slightly more gouging action of a finger/fingernail would use the flat angled tip (ie picture 1). As I said I would use my finger for an odd job - but a workman might want/need something a little less delicate. [/guesswork]

Nonsense - the gaps are all the same. Behind a little flim-flammery your table is a simple arithmetic series with a0 = 0 and d = 0.1022009043 So if the "the way natural compaction works" is for the gaps to get smaller: and they clearly don't get smaller - is your theory toast? Self contradiction

Free4 - Swansont is of course right - you are still ignoring the energy. To be a little more explicit try searching on work-energy principle

I think they normally become clickable because they have the http prefix http://www.physics.u...ravitytrain.pdf

Be more precise. You have two problems. The first is solved - it provided the velocity when the arrow HIT the ground. Now, WRT problem 2, is that velocity the final velocity?? I was explicit in my previous post about velocities for second problem - re-read that post. You do have one more piece of information that is staring you in the face.

To get a link to be clickable you need to use the link button. Its just next to the smiley icon. Best way is to copy the link, type the description, highlight the description, hit the link button, paste the link in the dialog, click "insert link" and you have a nice clickable link Gravity Train . You will also have the problem that your link doesn't have http prefix - if you follow above instructions you need to make sure you include the http bit by inserting rather than overwriting in the dialog. Jeez I hope no one tried previous links in my first three attempts.

Hey - we're getting there. v=u+at BUT, and it's a big but, you don't know t ! So we need a different equation. - you know initial velocity (you just spent last hour calculating it!!) and you know final velocity (it's stopped) so you have v and u. What else were you told? There was a new piece of information so far unused that will allow you to use the equations of motion to calculate the deceleration.

I would agree with you if the question did not say "By considering the energies involved" - I cannot believe a higher education assignment would use wording like that if it didn't mean it. (or am I putting too much faith in the question setter? ) I would always do a question like this with what I learned as the suvat equations you have a mass term on each side of your equation... I hadn't read the last bit of your post - yep that's what I got. You can double check by using the equation v2=u2+2as - u is zero so you get v2 = 2as . You will notice this looks very like v2= 2gh and because g is a and h is s you realise it is the same.

would be interested to see any reviews from SFN - I saw it in the bookshop yesterday and was sorely tempted but I am still wading through Dworkin's latest opus and I don't think I could cope with both

As a further hint - take a look at this page on gravitational potential energy and this page on kinetic energy . You want to find a pair of simple equations for U and Ek which you can set to be equal and rearrange to give a simply equation for the velocity (actually velocity squared) in terms of the the height above the ground and g. You will then notice that this bears a striking resemblance to one of the equations of motion given earlier (if you make initial velocity zero which it is at apex) Come back if you are still struggling - but do put down where you have got to yourself

The question does state "By considering the energies involved" - now I would just use simple uniform acceleration equations of motion - but that will not answer the question as it has been asked. I think you need to consider the link between gravitational potential energy and kinetic energy - and explicitly show how the obvious equation of motion can be derived from the equality of PE and KE

Elas - you do realize that a list of masses as generated by your formula will predict every particle simply because it is a long list of numbers with a constant addition (.102something), the most you can be wrong by is .051ish; in fact your average error is actually slightly more than would be expected by using random numbers.

Negative rep for the above post!? (I have added +ve to cancel it out). I know the rep points are just a bit of fun, but showing your displeasure with a factual post because it casts doubts on one's presuppositions is very poor form for a science forum. Argue the point; sure, that's what the forum is for. But 'negative repping' should be retained for the wrong, the illogical or the plain stupid.

sysD - whilst I don't disagree with Mooey or the Capt. above I thought I would add my five cents; First off - think about what the 0.5 is doing to the function and especially when looking for roots. And you are looking for roots - I interpret your bouncing as two roots that are the same (ie y=x2 -4x +4 has two roots both at x=2), the line touches the axis but never cuts it (it stays either +ve or -ve) - and your cutting is when the curve intercepts the axis whilst moving from +ve to -ve or vice versa. Once you realise what the 0.5 on the outside contributes you can simplify and that is the name of the game. Secondly - the way the equation is given to you might ring some bells with some people that allow them to go straight to a solution , but if it is not then you need to grind it out. This means multiplying out brackets - putting like terms together to get standard polynomial form and then seeing if you can factor more normally. This is possible and doable for this function but boring. Thirdly - as a very vague hint, once you have done it the boring way go to wolfram alpha and try changing every -3 for a -4 or a -5 and take note of how the roots change. Then perhaps try changing the moddle coefficient to -2 and -1. This should allow you to see a neat way of factorising that give you the answer directly

facetiously and erroneously, as it turns out. What it actually says is as follows:

I presume this is the one referred to - the pre-print at arxiv , and a few pop-sci articles from New Scientist and Scientific American

Yep - not sure what I was thinking.