A Conversation for Gravity

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Post 21

Orcus

Centfigues? Centrifuges even smiley - smiley


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Post 22

Dr Hell

Yep PhD *sigh*...


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Post 23

Orcus

Ah. Good luck with it smiley - smiley
I passed that stage about 4 years ago thank god.
I'm "professional" now smiley - yikes.
If I had a penny for every person who suggested I go into business with them to make and sell narcotics...


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Post 24

Dr Hell

When I 'switched' to p-chem (I was a chemist doing biophysics before) everyone thought I was going nuts.

I think they were right.

How is it in the Bizz? Where are you working? Big Industry, hi-tech or something totally different?


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Post 25

Orcus

I'm a university post-doc. Academic research in other words. I'll try and get into the pharmaceutical industry soon as there jsut aren't any rewards for being an academic anymore - low pay, no perks, lots of out of hours working... not the best smiley - sadface
I get the university lifestyle still mind so thats one little bonus. But one day i'd like to stop being poor.


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Post 26

Hoovooloo

First, an apology. Hell, I did NOT mean to be personal. Plus I am appalled to find out I mocked your spelling in a language which is not your mother tongue. I totally, unreservedly take that back, your English is excellent. I was parochially assuming I was addressing an English speaker. Again, my apologies. But...
The whole centripetal/centrifugal thing. They AREN'T just the same thing. I was going to say that it's like saying experiencing the recoil of a gun and experiencing the impact of the bullet are the same thing - but even that doesn't work because both of those forces actually exist. In a rotating system, there's just ONE force, and it acts INWARDS. As it says in the thread on Centrifugal force, if you're inside that rotating system, centrifugal force (as well as Coriolis force) do appear to exist. This is simply a feature of rotating frames of reference. There is nothing generating an actual force which acts on the object.
As for jets and rockets, I'm beginning to wish I hadn't mentioned it! smiley - winkeye
I hope you can accept my apology, I really did not mean to cause offence.


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Post 27

Dr Hell

I accept your apologies. Let us stay factual.

You have pointed out two 'mistakes' in the gravity entry:

(a) Jets do not work in space
We came to the conclusion that I was thinking about fire extinguisher-like jets, and you were talking about airplane jets... That point is clear to me. And it is NOT in the 'Gravity' entry. SO it is not a 'mistake' in the gravity entry.

(b) Centrifugal & Centripetal forces:
They are the same nature.(Different signs of course - my mistake, I just was not focussing on that) When you sit on a chair you cannot tell if your bottom is acting a force upon the chair, or if it is the chair that is pushing your bottom up. It is the same with centrifugal force. If you are inside a rotating donut (on the outmost part -- like in the space-station in 2001[the film]) and have no windows, you could not tell that you are rotating, and you would think that there is some kind of a 'magnet' outside pulling the falling objects to the floor.

Another example: Imagine we were holding a rope and then start moving about eachother The center being the little (+) there. (Oh yes and we are in space, with no stars around to tell us we are rotating - so we are not getting dizzy and we would swear we are not moving.

YOU-(your arm)---------(+)---------(my arm)-ME


You will be pulling me and I will be pulling you. From my view I am acting against your FLEEING. If I release the rope you will move away from me. From MY point of view tehre was a force acting on you *I* would call 'A force pulling you away'. You would of course think the same. If you *THOUGHT* that I was fix and it was you that were rotating around me, then you would say that there is a force PULLING YOU, which on release stopped to act on you, and that is why you are moving away.-- What I am trying to expose here is that it DEPENDS on your point of view, and what you are trying to describe. I am sorry if that is a common misconception in the english school-system.

The centrifugal force is a valid concept.

Thanks for listening,

HELL

PS: Even I I was a native english speaking person - your comments would still have been unfair and unethic. Some people have difficulties with typing, others just can't spell even if they are otherwise brilliantly sensible persons.


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Post 28

Hooloovoo


Hell,

Can I just point out that the person you've been talking to is "Hoovooloo". This is not me, my name is "Hooloovoo" which is actually the correct name for a super-intelligent shade of the colour blue, as in Douglas Adams HitchHikers Guide. I'm assuming the message you posted on my page was not actually meant for me. The other guy, Hoovooloo, cant be that super-intelligent if he cant even spell his own name correctly.

I really can't be bothered to get into this argument, suffice to say that Hoovooloo clearly doesnt know what he is talking about. Oh, and coincidently enough, I am also a physics graduate.

The one and only Hooloovoo (anyone else is just an imposter).


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Post 29

Orcus

smiley - erm

Well *that* definitely confused me!

Can you two pleaser change your names to something more distinguishable now please? smiley - winkeye

smiley - biggrin


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Post 30

Dr Hell

Million Laughs...

I suspected something strange was going on...

Well then, I'll pay more attention,

HELL


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Post 31

Hooloovoo


Well since mine is the correct spelling, I think he should be the one to change his name..... Oh, and I'm known as Hooloovoo all over the net so I'm not about to change it smiley - tongueout

The one and only Hooloovoo (anyone else is just an imposter)


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Post 32

Hoovooloo

Simply saying that it's obvious I don't know what I'm talking about hardly counts as constructive criticism. Please be more specific. I have in fact had some constructive criticism here, so more would be very welcome - if you have any. I would also point out that the only reason that there is any confusion here at all is that when Hell decided to go on the "attack" (and I must stress that this is his term for it, not mine), he couldn't even be bothered to check that he was attacking the correct person. Which is interesting given that there is a clickable link at the top of every single message I've sent to this and every other forum, so he didn't actually even need to do that. I don't feel the need to change my ID, I used this spelling purposely because I prefer the sound of it, and in any case I was here first! smiley - winkeye


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Post 33

Marjin, After a long time of procrastination back lurking

Gentlepeople,
I was really surprised to see such a violent discussion by the same people that seemed so civil in the discussions about centrifugal/centripetal and coriolis forces.
And just because of a few errors in an otherwise good entry.
Shall we please return to the entry itself?

To get into space a spaceship (good name) has to use engines of some kind that throw out matter at high speed. To stay up there it has to get enough hight and speed to get into a Kepplerian orbit completely outside the atmosphere. After that it can again use its engines to reach escape speed from the earth (like the probes going to the other planets).
For the part ith the trick at sea-level, I think we should put a full-stop after the word 'molecules', and delete the rest of the sentence.

As an extra, rocket engines are more efficient in a vacuum than inside the atmosphere.

Bye the way, english isn't my native language either and I did graduate in physics (some 30 years ago).


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Post 34

Orcus

Hey chill out about your names you guys.

It was a *joke* smiley - smiley


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Post 35

Hoovooloo

Marijn: completely agree with everything in your last post!
Orcus: smiley at end of my post was meant to indicate that I'm only amused by all the "name confusion" stuff, not annoyed in the least! smiley - winkeye


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Post 36

Marjin, After a long time of procrastination back lurking

You got me. A few minutes ago I answered you (or at least someone calling himself Hoovooloo) in the coriolis discussion, and I felt desperate, what kind of guy is this.
Are you sure you are the same Hoovooloo?


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Post 37

Hoovooloo

Yeah, same guy, just one guy. Why did you feel desperate? Please tell me it's just because I seem a bit slow and that you're not getting through to me, because if it's something else I'll be worried, I think...

btw, I know it's "Hooloovoo" in the book. I prefer the sound when the v comes before the l (sounds a bit like "voodoo", to me anyway...), and besides, since I signed up someone else has come along and taken the correct spelling.


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Post 38

Dr Hell

... The gravity entry is then correct (apart from the semantics, or possibly misleading explanations).

I'm leaving this thread to discuss forces somewhere else.
(The people involved probably know where.)

Bye, see you around...

HELL


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Post 39

Marjin, After a long time of procrastination back lurking

Hooloovoo,
I probably answered your question in the coriolis discussion, there seems to be a fundamental difference in our way of thinking.
So lets meet again somewhere, sometime, somehow.


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Post 40

Hooloovoo


> Hooloovoo,
> I probably answered your question in the coriolis discussion, there > seems to be a fundamental difference in our way of thinking.
> So lets meet again somewhere, sometime, somehow.

Remember, you're talking to HOOVOOLOO not ME. That post above is not to me, its to the other guy. Please try to GET IT RIGHT!!


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