Talk:G-force

This article needs to more clearly distinguish (without making separate articles for any of them) between the use of g for:

a variable, or a particular measurement of a variable quantity
- this includes the "local" acceleration of gravity
- these sometimes use subscripts, as when the value is for the equator or for the poles or for sea level at some particular latitude on earth, or to identify a typical value for some other planet
a constant, which should always be written with a subscript (for "standard acceleration of gravity (or of free fall)," g_n is the modern preference of the standards bodies such as ISO, NIST, and IUPAP, I think)
- this g_n is a concept of metrology, not of physics; it serves no purpose other than to define a unit of force based on a unit of mass under earth's gravity
- another related but slightly different constant is various values of g_c used as conversion factors to make units work with a particular system of units which is not a coherent system
a non-SI unit of measure

Another distinction is between the use of a word and the pronunciation of the letter used as a symbol. While this is usually difficult to make, I would say that when it is used in a plural form it should be treated as a English word and spelled out "gees" rather than improperly adding a language-specific 's' to a symbol for a variable. However, it shouldn't often be used in plural form, except in direct quotes or discussions of that usage.

Gene Nygaard 13:21, 12 Dec 2004 (UTC)

32.2 ft/s/s

32.2 ft/s/s or a more accurate british unit should be added

"Kepler's Laws of Planetary Motion are presented as empirical deductions from data; The nature of the required force is deduced from the centripetal force law and Newton's Third Law"

http://www.iit.edu/~smile/ph8615.html

G-force?

Where does the name G-force come from? It's not a force. Or is it? If I'm jumping out the window, during free fall, do I experience 1g (an acceleration) or 0g (a force)? Similarly, right now, sitting on my ass, do I experience 1g or 0g? AxelBoldt 02:31, 6 September 2005 (UTC)[reply]

Whether sitting or in free fall near the surface of the earth, a force of 1G is being applied. In, free fall, that force translates to accelerated downward speed. Sitting, that force translates into a force on the buttocks. Samw 03:20, 6 September 2005 (UTC)[reply]

So g is a force, not an acceleration? Then the units in the article are wrong. AxelBoldt 03:28, 6 September 2005 (UTC)[reply]

Note the difference in g and G in Samw's answer. See the article:

The symbol g is properly written in lowercase and italic, to distinguish it from the symbol G, the gravitational constant, which is always written in uppercase and italic.

g is an accelleration, G is the force that causes the accelleration. So sitting applies a force of 1G on your body, the floor prevents you from accellerating. If the floor was gone, still 1G is applied to your body and you would fall, your speed accellerating with g. Felsir 06:27, September 6, 2005 (UTC)

Wrong!

G = F·r²/(m₁·m₂) where F is a force.

But what you are talking about is 1 gee (acceleration as multiples of a "standard" acceleration of gravity g_n; the symbol g without a subscript is used for variable local accelerations of gravity), not 1 G, a constant never used as a unit of measure. Talking about 3 G is senseless; talking about 3 g is merely a hangover from the use of archaic, screwball Earth-based gravitational systems of units. Gene Nygaard 09:51, 6 September 2005 (UTC)[reply]

So g is truly an acceleration? As I sit right now, I therefore experience 0g? So what about the term g-force? AxelBoldt 19:26, 6 September 2005 (UTC)[reply]

A physicist would say that, sitting on your ass, you are experiencing an acceleration (not a force) of 1 g pulling you downwards. This acceleration consists of just over 1 g due to Earth's gravity, less a tiny bit due to the Earth's rotation. An aviator, either not knowing or not caring about these niceties, would say that you are experiencing 0 g, by which he means 0 g in addition to everyday gravity/rotation. It's a bit like tyre pressures: when your gauge says 30 bar, it means 30 bar above atmospheric pressure, but a physicist would say the pressure inside your tyre is 31 bar.

Journalists talk about "g-forces" presumably because they confuse the force due to acceleration with the acceleration itself. Force = (mass of your ass) x (your acceleration). --Heron 20:15, 6 September 2005 (UTC)[reply]

"A physicist would say that, sitting on your ass, you are experiencing an acceleration (not a force) of 1 g pulling you downwards." I find that statement very strange. First of all, accelerations don't "pull"; an acceleration is simply a change in velocity. My sitting ass's velocity doesn't change (except for the rotation of the Earth, its revolution around the Sun and the Sun's revolution around the Milky Way), so I would assume that my acceleration is close to 0g.

But I think you are onto something with the tyre pressure example. Maybe we have to exchange physicists and aviators? AxelBoldt 15:43, 7 September 2005 (UTC)[reply]

My statement may have sounded weird, and after your objection I thought for a while that I had got it wrong, but then I read a few articles on relativity that gave me confidence that I was right. I was trying to point out the equivalence of acceleration and gravity, which means that, if you shut your eyes, you can't tell whether you're on a stationary planet or a platform that's accelerating upwards. This is the strong equivalence principle (EP) of general relativity (and I'd be lying if I claimed to understand it fully). If you read the Wikipedia article on the EP, you will find that, merely by sitting on a planet, you are effectively accelerating. In other words, you can't say that acceleration caused by movement is different from that due to gravity, because what looks like movement to one observer might look like "sitting on your ass" to another. This is so counter-intuitive that there are still people who argue against it, but my money is on Einstein. I'm sorry if I have overcomplicated the issue by bringing in relativity, but if I can't be pedantic on Wikipedia, then where can I? ;-) --Heron 19:16, 7 September 2005 (UTC)[reply]

" if I can't be pedantic on Wikipedia, then where can I? " Ok, that inspired me to respond. Concerning the acceleration of sitting in a chair, some of what is said above is correct, but allow me to explain it in hopefully understandable way. It's simple. You sit in a chair, not moving , so your acceleration is 0, so by F=ma your TOTAL FORCE is 0, but you are experiencing a force of g * (your mass) downward, so there is a counter force of the chair pushing up on you = - g *(your mass). So you are experiencing a "1-g force" down, which is just a shorthand terminology for saying "1-g * yourmass" force down. (Pedantically, g is an acceleraton, not a force.) GangofOne 23:45, 11 September 2005 (UTC)[reply]

Geeforce redirect

just wanted to note her that the article Geeforce has been redirected here as per consensus on Wikipedia:Articles for deletion/Geeforce, there were several votes to merge as well in case anyone is interested in merging the contents over. Jtkiefer ^{T | @ | C} ----- 01:07, 20 September 2005 (UTC)[reply]

Gee?

I've never seen this written "Gee" (or "gee"). It's possible some people do, but it's definitely much less common than g. Accordingly, IMO this should be moved to g (physical constant) or similar. --Delirium 00:58, 7 October 2005 (UTC)[reply]

I support this. However, I thought Wikipedia article titles couldn't start with lower case? "Gee" then isn't a bad alternative. "Gee force" is fairly common. Samw 01:13, 7 October 2005 (UTC)[reply]

Keep it where it is, not only for the reason given by Samw, but also for the same reasons Pi was kept where it is despite efforts to change it, the reason CmH2O was moved to the spelled out name, etc.

This, of course, is also not really a "physical constant" at all. It is a "metrological" constant only. Of course, there is a G that really is a physical constant, and because of that simple fact, Samw's reasoning is really important in this case. That one, of course, can be found in the gravitational constant article. Gene Nygaard 03:30, 7 October 2005 (UTC)[reply]

Pi actually is the spelled out name though; that's the name of the Greek letter. By constrast, "gee" is not the name of anything (unlike Greek letters, Latin letters in English don't have ways of "spelling them out"—α is spelled "alpha" in Greek, but a is not spelled "aiee" or "ay" in English, except perhaps informally). I've certainly never seen a textbook include anything about a "gee force". --Delirium 14:51, 7 October 2005 (UTC)[reply]

I was really suprised to find this at "gee" too. Never heard it called that. It belongs either at "g" which of course would be G, or at acceleration due to gravity. moink 05:12, 17 March 2006 (UTC)[reply]

centrifugal force?

I dispute this article's claim that the equatorial bulge is caused by "centrifugal force". I see this a lot and it drives me nuts. Physics denies the very existence of a 'centrifugal' force. There is no force pushing objects outward in a centrifuge or spin period. The outward motion is due to the object's inertia and momentum.

The equatorial bulge is due mostly to the materials inside the Earth flattening out due to their inertia. Like water in a bucket spun overhead, the material is stopped by the barrier holding it(for the water: the bucket and for the Earth: the harder, outer layers). -Horse