studiot

So why does it go down ?

I don't believe I said any of this. Clearly the countermomentum must act over the same timespan so nothing is moving 60 times faster. But the scale spring or whatever must have stiffness so that the movement of its scale over that same timespan is only some fraction of the moving mass of the body. I'm also not saying that when straightening up the bulk of the body mass moves anything like 1 metre. If you are refering to the video it involved starting flatfooted on the scale and raising the body slowly to tiptoe, about 0.1m or 1/10 of that figure. I also asked for some help posting a short video of the scale acting as I described. Photographs I can do but they are not useful in this case.

Are you another Science Fiction Author looking for help ? Quite a few have been helped here. Or are you referring to Genesis 1:2 ? Or what is your purpose ?

+1 I said it is complicated. Thankfully the English language has (nearly) the wherewithall to deal with the subject. I have already pointed out the connection between time and existence.

I found this article and measurement of the reaction force from the ground on a person performing a standing jump. https://www.researchgate.net/figure/Dynamic-and-kinematic-curves-for-the-countermovement-jump-sample-output_fig1_233734813 It includes this force plot I have highlighted in pink. Note the researchers recorded a dip, as I did. I agree, Newton rules OK. How about this. You stand on the scale You are quite still. So the vertical momentum is zero. You lunge upwards, acquiring vertical momentum. Then come to a halt and are again still. Before and after the vertical momentum is zero. During the upward lunge this must still be true ie there must be a counterbalancing downward momentum somewhere. In the scale mechanism. So the mechanism reads a lowering of weight. The faster the upward lunger the greater the rate of change of vertical momentum and the the greater the corresponding reduction in scale reading. I am far from an expert in human body mechanics so I would welcome comments from those who are as to how this might work.

I wish it was as simple as you seem to think. First off 'does' is the present tense of a verb. Are you including other tenses Will my dinner exist tomorrow ? Did the dinosaurs exist ? Then the there is the subject, which is a noun. English nounds can be concrete,( like your apple) or abstract Does Harry Potter exist ? Does my reflection in a mirror 'exist' ? Does the centre of a torus (donut) exist ? So context please ?

I think you need to provide substantially more context to engender a sensible discussion.

No it does not mean that at all. You 40 page document derives analytical conditions for a simplified model in one dimension. Note this analysis is compatible with my attachment which uses Poisson's equation for the flow. The simplest model is Laplace's equation [math]{\nabla ^2}\left( \Phi \right) = 0[/math] This does not account for interaction between paticles so for a stream must be replaced by Poisson'r equations [math]{\nabla ^2}\left( \Phi \right) = f\left( \Phi \right)[/math] Where phi is a suitable flow variable. Do I understand you are interested in the the method outlined in your eference document here is the summary whihc would have been useful for you to post I have emboldended the important descriptive sentence.

I'm guessing you are studying high school physics or applied maths, and what you are referring to is the vertical acceleration due to gravity felt by all material bodies on Earth. This is normally given the symbol g and has an (average) metric value of 9.81 metres per second per second, you you are correct this is an acceleration.

Gosh it's a long time since I looked at this subject. I think some more information is required. What do you mean by flowing gases ? The electron ballistics of vacuum or near vacuum devices and those which have an appreciable gas fill are quite different. Also relevant is the question of what frequency are you working at D.C. or (ie zero) or some A.C. frequency. You have mentioned space charge, which normally refers to a particular effect in such tubes, not the charge density of the flowing current. Please confirm what you actually mean. I'm guessing but are you referring to this ?

Oi! I was just about to write that +1 @ChrisShield FYI our moon's gravity is only 16.6% of Earths. I would think that 5k years would be enough for lunar inhabitants to have diverged biologically in the lower gravity. Also our moon keeps one side towards the Earth so its day and night are 14 earth days/nights long. Plenty of scope in the imagination in variations of those two facts to play with.

Thanks to iNow for introducing the subject, sensei for those comments I value highly and others who replied. So the price of innocnce is eternal vigilance. Where have I heard that before ? Edit I have just started 'following' the new member concerned. This is the first and probably only time I will do this as I have never seen any use for the facility on a forum. When I clicked on follow I was offered a tickebox to 'Let othere see you are following' Perhaps we should include the significance of this in the scrutiny ?

Like this ? Maybe @Sensei has some ideas ?

Confucious he says "He who is downright rude and dismissive to all around him soon ends up with egg on his face". You said Which means that all biological life (whatever that tautology means) ........ and added the rider '100% true'. Not some life or even nearly all life but 100% of life will encouter difficulties with survival. The dinosaur mass extinction (K-T event) was not even the greatest mass extinction in Earth's history - that distinction goes to the Permian - Triassic (P-T) event. But neither was 100% So life survived.

Perhaps joigus cannot dispute the correctness this statement, for he is a Physicist. But I can because it is just plain wrong. To the best of our knowledge Paleoclimatology tells us that the Earth has only had its present nitrogen/oxygen atmosphere for less than half its existence. And the oxygen was not a component of the original atmosphere. The oxygen was actually released as a waste product from lifeforms that existed before oxygen for example stromatolites. Naturally the climate was also different then. So if the climate changed again, so would 'biological life', but it would probably still thrive, just as it has done before.

Hey Seth, I was trying to give you the opportunity to expand on your statements. That is to note that H and G are both state functions, ie they refer to the system itself, and in themselves can be (are) defined as postive. But ΔH and ΔG ie changes of H and G are not, they refer to processes not the system itself. Also I should have said sign conventions ( I did consider going back and adding the s but I was too lazy) since the difficulties arise as there is not a single sign convention in fact, but two in play simultaneously. This is because you ahve to have a convention to determine whether you are talking about work done on the system or by the system And a second convention to determine which you call this positive and which negative.

Now you are just trying to be a smart-alec. The rest of your post completely avoids the vicious false accusation you made upon myself. This is a false accusation that is not borne out by my few posts in this thread which suggest I came to both learn and discuss. I started by declaring that I was no expert and offering what little I knew about the subject for discussion. You have just responded to a later post where I thanked you for something I have learned.

This is a false accusation that is not borne out by my few posts in this thread which suggest I came to both learn and discuss. I started by declaring that I was no expert and offering what little I knew about the subject for discussion. You have just responded to a later post where I thanked you for something I have learned.

Actually joigus, the Oxford English Dictionary makes it quite plain that the verb 'needs' can be applied to a person or a thing way back to medieval times. There is no special distinction so your example is perfectly correct common English ie not very special. It is, however worth pointing out to the OP that on a technical site like SF, many words do have a special technical meaning. And many disagreements and misunderstandings arise from folks not being careful to distinguish. I do not know of a special technical meaning, so I think that your use of the common Englisn 'needs' is fine, but it would be unfair to knowingly misdirect someone whose first languauge is not English by misuse. Even someone whose Engish is as impeccable as that of joigus.

Actually, thank you. For introducing me to a new term I had never heard of. I take it that is what you are doing here in particular to a group of individuals.

What sign convention are you using here please ?

Did you hear the one about a psychologist ? She joined a Science club and was obnoxious about Science just to laugh at the mayhem she could cause. Goodnight all it's past the witching hour here.

+1 🙂

One thing you can say for the Laws of Physics. They hold good in China as well as California. The DSM doesn't hold in most places ouside the US. In fact in the short series of lectures I attended they took pains to point out its shortcomings.

I have been wanting to use the acronym LOL for a while so here goes. I think that coming to a Science forum and opening a question in the Physics section entitled Questions on Thermodynamic Free Energy and then complaining there are other uses for the word Law is equivalent to me taking my book of Mathematical Tables off the shelf, opening it at the table entitled "squares, roots and reciprocals" and complaining that it doesn't show the sine of the argument (do you know what an argument is in mathematics ?). You say you have an interest in Earth Science. Do you know what the word Law stand for in the home of Earth Science, Scotland ?