Talk:Mechanical energy

message: :Energy is a state function and work is not. That is covered under those terms. Mechanical energy and mechanical work should be separate articles and not merged. I don't have time to improve this article right now, and it's properly labeled as a stub. I'm removing the merge tag and adding the expansion tag here. Flying Jazz 02:56, 30 December 2005 (UTC)
replies: text: Agree.  As regards the stub tag, though, I'm not sure what more there is to say. --Smack (talk) 17:10, 30 December 2005 (UTC)
thread_title: Problems

message: I would like to remove the expansion request.  This article should give people a general idea of what's going on, and point them to one of the articles in the see-also list. --Smack (talk) 06:46, 29 January 2006 (UTC)
thread_title:  Expansion request removal 

message: Good grief; entire textbooks could be written on this subject.  This is definitely a fundamental topic that schoolchildren will look up and will need help understanding.  This article should give a clear explanation of the concept, with examples, without depending on other articles for necessary background.  I've an article from scratch to try and do this.  The next thing to add would probably be illustrations. -- Beland 23:18, 5 March 2006 (UTC)
replies: text: Looks pretty decent.  Now if someone could reconcile it with mechanical work, so that they refer to each other in the right places and don't duplicate anything that they shouldn't, it would be really nice. --Smack (talk) 04:41, 8 March 2006 (UTC)
thread_title:  Expansion request filled 

message: I was reading through this and I don't think I can find an actual clear definition of the term.  Not anything special, just have it set in stone.  "Mechanical energy is..."
That's all for now...
DUbblecoMB 18:55, 9 May 2007 (UTC)
thread_title:  An actual definition 

message: This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:00, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: I don't really have time to write this article, but "the principle of general conservation of energy is so far an unbroken rule of physics - as far as we know, energy cannot be created or destroyed, only changed in form"?!! E=mc^2??? That's embarassing, but i'll leaveit so others can see it was, in fact, actually on this page. But I should stop talking, since I don't have time to do anything about it. . .  —Preceding unsigned comment added by Drock2289 (talk • contribs) 05:12, 8 April 2008 (UTC)
thread_title: Wow

message: Can I translate into Tamil? Mahesh967787 (talk) 12:15, 22 February 2019 (UTC)
thread_title:  Tamil 

message: On 30 September 2020 User:Julian Benali made a minor amendment to this article. His edit summary says “Elastic/Inelastic refers only to kinetic energy. Total mechanical energy may or may not be conserved during inelastic collisions.” See his diff. I challenged the notion that mechanical energy may be conserved in an inelastic collision.
I reverted this good-faith edit but Julian and I ended up discussing it in depth on his Talk page. See User talk:Julian Benali#Mechanical energy. His explanation of his statement “Total mechanical energy may or may not be conserved during inelastic collisions” makes use of Classical Mechanics by John Taylor. (This source is not currently cited in the article, and I don't have access to a copy.)
Julian has written “For an example of an inelastic collision where mechanical energy is conserved, see problem 4.53 in John Taylor” 
:4.53** (a) Consider an electron (charge -e and mass m) in a circular orbit of radius r around a fixed proton (charge +e). Remembering that the inward Coulomb force ke^2/r^2 is what gives the electron its centripetal acceleration, prove that the electron's KE is equal to -\tfrac{1}{2} times its PE; that is, T=-\tfrac{1}{2}U and hence E=\tfrac{1}{2}U. Now consider the following inelastic collision of an electron with a hydrogen atom: Electron number 1 is in a circular orbit of radius r around a fixed proton. (This is the hydrogen atom.) Electron 2 approaches from afar with kinetic energy T_2. When the second electron hits the atom, the first electron is knocked free, and the second is captured in a circular orbit of radius r'. (b) Write down an expression for the total energy of the three-particle system in general. (Your answer should contain five terms, three PEs but only two KEs, since the proton is considered fixed.) (c) Identify the values of all five terms and the total energy E long before the collision occurs, and again long after it is all over. What is the KE of the outgoing electron 1 once it is far away? Give your answers in terms of the variables T_2, r, and r'.
:Indeed, mechanical energy is conserved in this scenario even though kinetic energy is not and the method for solving part (c) is to invoke conservation of mechanical energy. Thus, the total mechanical energy may or may not be conserved in an inelastic collision.
My understanding of mechanical energy is confined to situations where an object’s potential energy is due solely to the gravitational field. In example 4.53 quoted above, the potential energy of protons and electrons is also due partly to an electric field. This appears to be the clue to understanding Julian’s edit summary.
I am persuaded by the logic expressed by Julian Benali and John Taylor so I will erase my most recent edit and restore the article to the version established by Julian. I am grateful to Julian for introducing this improvement into the article. Dolphin (t) 12:23, 5 October 2020 (UTC)
replies: text: I have now erased my most recent edit. See my diff. Dolphin (t) 12:28, 5 October 2020 (UTC)
thread_title:  Inelastic collisions 

message: An important issue related to the conservation of mechanical energy is presently under discussion at Wikipedia talk:WikiProject Physics#Inconsistencies related to mechanical energy. Dolphin (t) 13:56, 1 December 2022 (UTC)
replies: text: The discussion is now archived at Wikipedia talk:WikiProject Physics/Archive December 2022#Inconsistencies related to mechanical energy. Dolphin (t) 21:28, 27 January 2023 (UTC)
thread_title:  Conservation of mechanical energy