Talk:Equations for a falling body

message: what would be great- imho
if the article confined itself to the math, but for each of the equations had two references: one to a page where the equation is derived and one to a page of the most relevant history of that derivation. 209.77.152.101 (talk) 14:25, 28 January 2016 (UTC)
thread_title: Untitled

message: I don't like how it uses Earth's acceleration due to gravity. Should the equations be changed to these?
Distance d travelled by an object falling for time t:                                        	\  d=\frac{Gmt^2}{2r^2}
Time t taken for an object to fall distance d:                                               	\   t =\ \sqrt {\frac{2dr^2}{Gm}}
Instantaneous velocity vi of a falling object after elapsed time t:                     	\  v_i = \frac{Gmt}{r^2}
Instantaneous velocity vi of a falling object that has travelled distance d:                 	\ v_i = \sqrt {\frac{2Gmd}{r^2}}\
Average velocity va of an object that has been falling for time t  (averaged over time):	\  v_a =\frac{Gmt}{2r^2}
Average velocity va of a falling object that has travelled distance d (averaged over time):  	\  v_a  =\frac{ \sqrt {2Gmd}}{2r} \
with G being the gravitational constant and r being the distance from the center of the main body
Tell me if I made a mistake in these, I'm not used to working with Wikipedia's math coding. Yanah 20:40, 17 October 2006 (UTC)
replies: text: Well, g is more convenient than GM/r2 for Earth uses. I would favor the equations in terms of g, with the qualifier that for other planets and for significantly different radii than Earth's, g must be replaced with GM/r2 where the M and r are chosen appropriately as other than Earth-surface normal. SBHarris 22:39, 17 October 2006 (UTC)
thread_title:  Possibly change equations? 

message: People have survived falls from airplanes and from tall buildings.
http://www.nytimes.com/2008/01/04/nyregion/04fall.html?pagewanted=2&ei=5087&em&en=a6cd1e14f02e1178&ex=1199595600 New York Times January/4/2008: Man survives fall from 47-story building.
--Ancheta Wis (talk) 19:50, 4 January 2008 (UTC)
thread_title:  Might this get into the article? 

message: Galileo was the first to demonstrate and then formulate these equations. Not according to the Wikipedia article Two New Sciences. At least not as far as one of them is concerned. Eroica (talk) 13:15, 8 July 2010 (UTC)
thread_title:  Galileo's priority? 

message: Just thinking; the following are either ignored or missed while formulating the equation for falling mass.
An equation of instantaneous velocity for falling mass is v = g x t in which a magnitude of 9.8 m/s/s [acceleration] can't be preceded in the very first infinitesimal falling of an object as g also incepts from zero [besides v and t] and should increase gradually to its constant value of 9.8 m/s/s.
Similarly "v" is directly proportional to "t"  but there is no chance at all for the numerical value of v to meet with numerical value of t in the very first development of mass falling as v is always ahead of t at 9.8 times t [9.8xt].
Since g = GM/R^2; where M =  mass of earth and R = the on centre distance between gravitating earth and a resting mass [radius of earth]. So this means g decreases by increasing the on centre distance of masses and also it is an axiomatic truth that g decreases with altitude.
Therefore should there be any range beyond which it starts varying in equation.68.147.41.231 (talk) 18:36, 3 November 2010 (UTC)
replies: text: The equation v = gt presumes that g is constant, and is not valid over regions where r changes enough that g varies (your second equation). SBHarris 19:42, 3 November 2010 (UTC)

text: Over a distance where the radius (R) changes significantly, it is preferable to integrate the variable force (g) over the change in radius to obtain the work done by gravity, then equate this to the change in energy.  Over short ranges, the simple equations give the same answer to a good degree of accuracy.  It is wrong to say that g starts from zero.  It is equal to GM/R^2 before the body starts to fall.   Dbfirs 08:27, 28 December 2010 (UTC)

text: On the contrary, Newton claimed the "inverse square law" in his Philosophiae Naturalis Principia Mathematica , and Robert Hooke claimed that he had previously devised this law in the early 1660s (though he hadn't done the mathematics), and the thinking of both geniuses was based on Kepler's area law, based on the observations of Tycho Brahe.  Of course, we are still looking for the "true picture", but the simple equations of motion under gravity will never be superseded for simple calculations in a gravitational field that is almost constant.  Dbfirs 07:49, 4 January 2011 (UTC)
thread_title:  Equations for a falling body  

message: It would be an intersting if we can trace/ record an instanateneous velocity/ g of of falling object with the help of speed gun placed on the ground facing up right towards the falling object with the help of other electronic arrangement which can precisely record covered distance and time. I hope it wouldn't agaist the rule.68.147.41.231 (talk) 08:55, 16 January 2011 (UTC)
thread_title:  How is the idea of Speed Gun 

message: Galileo was first to demonstrate that in the absence of air, all things would truly fall with the same acceleration and 300 years later demonstrated this by the crew of Apollo-15 on the lunar surface (which has gravity & also lacks air) by dropping a hammer and a feather. 
Assume hammer and feather dropped simultaneously from same ANTIPODEAN altitude. As moon can be seen from two different gravitational fields ["gf" of feather "gh" of hammer] therefore cognizance shows that hammer and moon should strike each other first as gh > gf  68.147.43.159 (talk) 06:30, 4 November 2011 (UTC)
replies: text: "This assumption is reasonable for objects falling to earth over the relatively short vertical distances of our everyday experience, but is very much untrue over larger distances, such as spacecraft trajectories.". So... you're right.  — Preceding unsigned comment added by 94.36.161.252 (talk) 15:06, 28 August 2012 (UTC)
thread_title:  Is Galileo's statement correct, theoretically? 

message: Sorry if I'm missing something here, but I was using this article to help check some gravity equations and ran across this paragraph:
"For astronomical bodies other than Earth, and for short distances of fall at other than "ground" level, g in the above equations may be replaced by G(M+m)/r² where G is the gravitational constant, M is the mass of the astronomical body, m is the mass of the falling body, and r is the radius from the falling object to the center of the body."
According to the page on the Gravitational constant, that should be G(Mm)/r^2. Is this an error/typo? If not why are the masses added here instead of multiplied as in other calculations for g? Also, isn't that first part irrelevant since it still applies to Earth? It just allows for the calculation of g rather than plugging it in as a constant.  — Preceding unsigned comment added by 173.85.79.164 (talk) 01:09, 6 March 2015 (UTC)
thread_title:  Adding mass instead of multiplying? 

message: Why is the Acoustic Fall Time vs. Height figure here?  The article provides no explanation for the figure.  What is the relevance of "Acoustic"?  And most important, why are there disparities between the data and the prediction?  The disparities are clearly not due to air resistance or some other parameter that would cause error in a consistent direction.  Haven't there been experiments with more accurate results?192.249.47.204 (talk) 19:38, 28 June 2017 (UTC)
thread_title:  Problems with Acoustic Fall Time vs. Height 

message: I would like for there to be an equation that takes into account both changes in G and also a starting velocity, both away and towards the central object.  — Preceding unsigned comment added by 76.93.160.48 (talk) 04:20, 9 March 2019 (UTC)
thread_title:  What about starting velocity?