Talk:G-force

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1 contradictions
2 GeForce
3 Incorrect Physics
4 g-force a force?
5 g divided by time
6 Equivalent versions of Helmert's equation
7 Helmert's equation superceded?

[edit] contradictions

Any exposure to around 100 g or more, even if momentary, is likely to be lethal.

Formula One race car driver David Purley survived an estimated 179.8 g in 1977 when he decelerated from 172 km·h−1 (107 mph) to 0 in a distance of 66 cm (26 inches) after his throttle got stuck wide open and he hit a wall.

Not necessarily: The first means "Don't try this at home", the second means "but you might get lucky" (roughly). I'd imagine that repeating the experiment is unlikely to be healthy. It is conceivable that restraints reduced the g force somewhat or otherwise made it more likely than usual to be safe. Ealex292 03:56, 1 December 2006 (UTC)

[edit] GeForce

People looking for the graphics card GeForce may end up on this page, as gforce redirects here. Just a note JayKeaton 15:01, 29 November 2006 (UTC)

[edit] Incorrect Physics

The article claims that the variations in the acceleration due to the gravity of the earth are due to so-called centrifugal forces. This is a poor explanation. I believe a better one would be:

One reason involves the difference in the distance from the centre of the Earth between the two positions due to the equatorial bulge – this leads to a variation in the gravitational field strength. The equator is further away from the centre of the Earth than the poles leading to a difference of about 0.05 m s–2. The second reason is due to the rotation of the Earth. The person on the equator experiences a centripetal acceleration. Given that the scales read the normal (or reaction) force N, in this case N = m(g–ac). Therefore there is a slight reduction (of the order of the first effect) —The preceding unsigned comment was added by 132.181.7.1 (talk • contribs).

[edit] g-force a force?

The article states in the introduction

g-force or g-load is a force-equivalent, equal to 9.80665 N/kg

but N/kg is a unit of acceleration, not of force, so I have to conclude that 1 g = 1 g-force. Is that intended? AxelBoldt 18:09, 19 December 2006 (UTC)

[edit] g divided by time

Shouldn't this article include the difference of g force divided by time?

There are great difference of experiencing 10 g's for a millisecond and for ten seconds. A person have experienced and survived over 46 g's in a certain amount of time, but it is lethal to experience for example 25 g's over a minute. This difference may not be understandable in this article.

[edit] Equivalent versions of Helmert's equation

It might be helpful to note that the version of Helmert's equation in the article is equivalent to the following (discounting rounding errors and expression of lengths in cm instead of meters):

http://lists.nau.edu/cgi-bin/wa?A2=ind0101&L=phys-l&P=39244

g = 980.616 - 2.5928*cos(2*phi) + 0.0069*cos^2(2*phi) - 3.086x10^(-6)*H

where: phi = latitude H = elevation (in cm)

This version is on several web pages and in a CRC Chemistry and Physics Handbook, where it can be difficult to find as noted here:

http://www.lhup.edu/~dsimanek/scenario/labman1/accel!.htm In a CRC handbook like mine, there's no index entry for Helmert's equation. Look up "acceleration due to gravity at any latitude and elevation, equation." It is in the "definitions and formulas" section.

The version above may be calculated more quickly because only one trig value is needed: cos(2*phi). Once that trig value is known, it can be squared for the third term. The version in the article requires calculating two trig values separately: sin(phi) and sin(2*phi).

It may be of interest that there is another, equivalent, version of this formula (with no double-angle trig arguments) which may be obtained by applying trig identities in yet another way. It has the form: g = g_0 * (1 + a * (sin(phi))^2 + b * (sin(phi))^4)

This latter version is not found as frequently on the web, but it is here: http://galitzin.mines.edu/INTROGP/notes_template.jsp?url=GRAV%2FNOTES%2Flcorrect.html&page=Gravity%3A%20Notes%3A%20Latitude%20Variation%20Corrections Ac44ck 07:33, 28 January 2007 (UTC)