Talk:Impulse (physics)

Old posts

 * I've moved the existing disambiguation information (small compared to the physics description) to a disambiguation line at the front of the article. I think this ought to be enough. However, it's always possible to create an impulse (disambiguation) article to deal with the alternative uses. Ian Cairns 18:08, 3 Oct 2004 (UTC)

The article does not mention Ns (Newton Seconds), which I believe is the more commonly used unit for impulse to distinguish between Momentum and impulse. It may be wise to state that Ns= kg m/s²x s = kg m/s, so while they are the same unit, Ns is used more frequently. Wheatleya 19:28, 9 November 2005 (UTC)

Fixed Terminology
First of all, impulse is not defined as change in momentum. (It's equal to the change in momentum of an object, but that's not the definition.) I put the definition first. Also, you don't say "an impulse..." any more than you say "a momentum". Impulse is a quantity. To say "an impulse is a change in momentum" makes it sound like impulse is an event, which is not correct, at least not in this context. Pfalstad 05:24, 19 April 2006 (UTC)


 * I think its perfectly fine to say "an impulse". It seems natural to say "apply an impulse". However, saying something to the effect of "apply a momentum" seems unnatural. I don't think that differentiating "an impulse" (in electronics) from "the impulse" or something (in physics) is a good way to differentiate them. Fresheneesz 07:11, 19 April 2006 (UTC)

Of course it's fine to say "an impulse", it's just not how the word is used in physics. Saying "apply an impulse" is using the word in a nontechnical sense. Unless you can provide a source (physics text) that uses the term in that way. Pfalstad 03:58, 21 April 2006 (UTC)

Disambig
I think this page should be a disambig page, and be moved to Impulse (physics). There are a bunch of other definitions of impulse, and impulse in physics isn't even a decently large concept. Any takers? Fresheneesz 07:11, 19 April 2006 (UTC)

removed outdated merge tag
I removed the merge tag, its old. And on the talk page for momentum - we are comming to the conclusion that we should move all that info here for good. Fresheneesz 08:21, 19 April 2006 (UTC)

Impulse (physics)
An article of this name was created today with a definition of impulse = rate of change of acceleration, instead of impulse = change in momentum. A merge was proposed, which I've boldy edited into a redirect to this article. I've saved the ext refs which confirmed the correct definition of impulse - as in this article as of now. Ian Cairns 00:43, 6 June 2006 (UTC)

Impulse is J or I?
I know this is really trivial, but shouldn't J be used to stand for impulse? that's what's used in my textbook Physics for scientists and Engineers with modern Physics, Douglas C Giancoli, Prentice Hall, Third edition (in case someone wants to look it up). 'I' stands for electric current, not impulse. (ever heard p=iv? that means power=current times voltage, not impulse times voltage). I think you are right when you say I stands for electric current but you can also use 'Imp' to mean impulse if you don't mind — Preceding unsigned comment added by Kaamuli vitus (talk • contribs) 06:18, 11 June 2015 (UTC)

are you sure?
are you sure that "dt is an infinitesimal amount of time"?

that is an integration statement, and "dt" would usually mean "with respect to t"


 * You are correct that dt is an integration statement of time, but the application of dt mean "the limit of time as it approaches zero", which means an infinitesimally small amount of time. Wizard191 16:46, 11 January 2007 (UTC)

What's a Hy unit?
Right now it claims that a N-m = Hy (Huygens), which is a unit name I have never heard of. Upon research I haven't found it used anywhere else on the internet or wikipedia. Moreover, the SI system doesn't reference it at all. If this is a real name of a unit please cite it, otherwise I propose that we remove it, as it is quite confusing. Wizard191 16:50, 11 January 2007 (UTC)

I looked everywhere for a unit of Hy. It sounds like a neat addition to physics, and one that the people who head up the SI units should add, unfortunately it is by no means official or correct. I'll continue to look out for it, but I'm removing it until it can be verified. 10 months of an unvalidated claim is quite long enough. —Preceding unsigned comment added by 129.22.18.156 (talk) 05:49, 7 October 2007 (UTC)

Adding to my comment above, the Hy is in fact a fictitious unit of momentum/impulse. It does not appear on the BIPM's website of offical SI units, and therefore it is false and should not appear on this page. —Preceding unsigned comment added by 129.22.147.117 (talk) 17:43, 8 October 2007 (UTC)


 * it's so seldom to actually compute a momentum of a moving body that there's no need for an extra unit, it's useless (if you need to just write Ns). though i've heard of the unit before (seen it pre 2006 in a german school book). given that it is a school book, there might be justification for a momentum-unit, since school books mostly don't go into real depth but do more of the "we get familiar with the quantities we use" stuff. so that might be a reason why someone made up the unit Hy. 92.196.80.110 (talk) 21:44, 12 September 2013 (UTC)

Force of Impact?
Often one hears the term "Force of Impact". Say you can calculate/estimate the impulse of an impact but you want to estimate (perhaps) the maximum force of collision, or possibly the average force of the collision, or maybe even the average force for the top 25% of the most forceful moments of the collision. Is any of that information relevant? I'm interested in the relationship between the fracture strength of materials and "how forceful" an impact an object of said material can take. It would seem that Impulse is a desired quantity to know, but what else should I know? IIRC to get average force, I just divide divide the impulse over the time it takes for the the impact to take place. But how would one estimate this time? How would I estimate the average force imparted by one billiard ball on another over the lifespan of the impact, which I cannot estimate with the unaided eye. How high could I drop a billiard ball in a frictionless environment from a building before cracks of a certain size develop on its surface (I.E. the force imparted exceeds locally the fracture strength of the material the billiard ball is made from but it does not fracture the ball). How do I estimate how much effect the ground chosen for the ball to impact has on this? If the fracture strength of the ground is quite low, energy from the impact will be dissipated by "flakes" of the ground being thrown outward, and it would seem that also needs to be taken into consideration.

It seems methods to estimate information is relevant and related to the article, but no description or references are included in the article. What quantities are these and how are they measured or estimated?

I'm not a physicist and I wouldn't even know where to begin to look (other than, say, research into stuff like bicycle helmets).

Root4(one) 17:46, 10 March 2007 (UTC)


 * This is now a question on Reference desk/Science. Root4(one) 04:03, 12 March 2007 (UTC)


 * Tough question. Many people will confuse you by saying double the static load. That's a bit weird, it makes lots of assumptions that are unsafe. The best way for many problems is to work out a stiffness function for the target, and an effective mass for the impactor, and to do a simulation of it. Greglocock 12:07, 13 March 2007 (UTC)


 * Answered on that page.Greglocock 01:11, 14 March 2007 (UTC)

Major rewrite
This article received several major revisions:

The general definition of impulse was moved to the beginning of the article, and the special case which once appeared there was moved lower down.

Reference to the "Theorem of Impulse and Momentum" was removed, since it is trivial (a three-line derivation appears in the very article) and does not even appear by that name in any of the mechanics textbooks I have: Kleppner & Kolenkow, Tipler, Young & Freedman, and Marion & Thornton. Mention of Newton's Second Law now precedes the derivation.

I added the fact that the special case given relies on both force and mass being constant; previously, only force was mentioned as constant. A common example in which the mass of a system is not constant is the problem of a rail car from which sand is leaking.

Finally, there were minor stylistic changes.

Anarchic Fox 20:05, 19 June 2007 (UTC)

Math?!
Who decided that Impulse defaults to the mechanical definition? Perhaps most people would be looking for the psychological definition? --Nathanael Bar-Aur L. (talk) 04:21, 24 August 2008 (UTC)


 * It appears most likely that the mechanical definition of Impulse was the first application of the word to be given an article in Wikipedia. The other applications, including Impulse (psychology) came after that.  When you select Impulse the top line in the article is a link to the Impulse (disambiguation) page.  This is a common solution found in Wikipedia for many concepts that have two or more applications.  If a Wiki User wants an alternative application to be the subject of the default article, or wants the disambiguation article to be the default, this is a legitimate topic to raise for discussion on the pertinent Talk page.  Dolphin51 (talk) 11:52, 24 August 2008 (UTC)

Context Tag: Introduction Needed
I have tagged this article as having insufficient context for readers with less understanding of the underlying physics and math involved in impulse, momentum and velocity. I'm not suggesting that the article needs to be "dumbed down", but if there's someone out there with good knowledge on this subject, I think this article could really use a well-written Introduction that explains Impulse in reasonably understandable prose, which could then lead in to the more technical explanation already contained within the article. Good examples of this would be the pages for Momentum and Velocity, which are both related to this article, and explain their concepts a bit better before jumping right in to the mathematical and theoretical explanations. TrufflesTheLamb (talk) 01:39, 22 January 2009 (UTC)
 * Thanks to Greglocock for putting together a well-written intro. I have removed the context tag; if anyone disagrees, please feel free to bring it up here! TrufflesTheLamb (talk) 18:15, 22 January 2009 (UTC)

Page move
Moving this page is a drastic action that I don't necessarily agree with. Can we please get this reverted and discuss this first? I don't see how this isn't the most prominent target. Wizard191 (talk) 22:23, 9 March 2010 (UTC)

Agreed. I've never heard the term Mechanical Impulse. Greglocock (talk) 00:54, 10 March 2010 (UTC)

Misuse of Notation
After the "therefore" statement in the "Mathematical derivation in the case of an object of constant mass" section, a misuse of notation is used to seemingly "cancel out" the 'dt's in the integration expression,. This should instead be a statement of the Second Fundamental Theorem of Calculus to derive the impulse-momentum theorem. While the "cancelling" is a subtlety that provides the correct results, it could mislead readers. A change could look like
 * $$\begin{align}

\mathbf{I} &= \int_{t_1}^{t_2} \frac{d\mathbf{p}}{dt}\, dt \\ &= \mathbf{p_2} - \mathbf{p_1} \\ &= \Delta \mathbf{p}, \end{align} $$ — Preceding unsigned comment added by 131.225.23.168 (talk) 07:08, 22 June 2012 (UTC)

Example section
The "Examples of impulse" section does not appear to add any useful information to the article, and is completely original research. I suggest that it be removed or reworked into something more concrete. - HectorAE (talk) 18:54, 5 March 2013 (UTC)
 * Agreed. Even worse, it's a collection of unconnected statements, half of which are wrong. &mdash;&thinsp; H HHIPPO  21:21, 5 March 2013 (UTC)

impulse, momentum, superfluous.
it's confusing to distinguish. for example, in german you don't distinguish between the two at all. it's the same (both are called "Impuls"). a moving body has a momentum. if you apply a force to it over a certain amount of time, you change its momentum (thus momentum has unit Ns = Hy, force times time). it's such a basic thing that it's unnecessary to make a big fuss about distinguishing between this. it doesn't help. the unit Ns = Hy is useless / never needed, unless it's the first lecture of mechanic and you want to work a bit with those basic expressions. you never actually calculate a momentum of a moving body and compare "oh look, this body has impulse 3 Ns", rather the velocity or relations between the momenta of two colliding bodies. put the stuff in this article in the momentum-article and delete this one, it's nonsense. 92.196.80.110 (talk) 21:37, 12 September 2013 (UTC)

and if you read the article carefully, you see that there is no content other than stating over and over that impulse and momentum are the same thing. it's artificial inflation of a trivial fact to article size. 92.196.80.110 (talk) 00:23, 13 September 2013 (UTC)


 * I am afraid you are wrong. Impulse is a change of momentum, not momentum itself. In English we find it useful to differentiate between the two, for instance with rockets. This is an English encyclopedia.Greglocock (talk) 01:15, 13 September 2013 (UTC)


 * "momentum" and "impulse" are also distinguished in german: momentum (en) = Impuls (ge) ≡ m v (to put it simple), impulse (en) = Kraftstoss (ge) ≡ F Δt (to put it simple), as stated in the article. Greglocock, impulse EQUALS a change of momentum (because of Newton 3) but impulse IS NOT change in momentum (the former is not defined ≡ to be the latter). Can we agree on that? By the way, it is the same with work and energy: work W equals a change in energy E, but it is defined as W ≡ F Δs. Herbmuell (talk) 00:33, 5 June 2015 (UTC)

Again: Impulse is J or I
Dear main authors; I believe the IUPAP is the authorative reference for notation in physics, not textbooks. In their RED BOOK (or SUNAMCO RED BOOK, it can be found with google), 1987 revision, 2010 reprint, they give only "I" for impulse (p. 28). The german Wikipedia accordingly uses "I". I suggest to change the "J" to "I" in the article. Regards: Herbmuell (talk) 00:57, 5 June 2015 (UTC)

Happy and sad balls
"Happy" and "sad" balls, as referenced in the video, are not standard terminology, and should instead be phrased in terms of elasticity. Or, since elasticity is not discussed elsewhere in the article, nor fundamentally relevant to impulse, this could be removed entirely. — Preceding unsigned comment added by 2601:482:8003:3468:811B:2E0B:C0BA:89DB (talk) 03:49, 23 October 2015 (UTC)


 * The terms happy/sad are defined in the reference, and the link still works. The names are a commercial gimmick used in the catalog that sells the balls, but they are of low cost and wonderful things to have in the classroom. It is plausible that WP would prefer that the terms happy/sad be omitted from the caption. Collisions have twice the delta-v, and hence deliver twice the momentum.  That makes the demonstration a direct (but qualitative) confirmation of the equation.  No other such demonstrations are readily available, so I believe the video should remain.   Disclosure: I worked with user:13hartc, the contributor of the video, on this project.  --Guy vandegrift (talk) 07:31, 23 October 2015 (UTC)


 * Since this is not backed by an explanation that makes it carry the desired message (it is a pedagogical example that fails to be pedagogical because it needs so much more context to interpret, such as elasticity, masses, etc., and WP is not meant to be pedagogical anyway), I have deleted this "sad" example. 172.82.47.242 (talk) 16:37, 8 September 2022 (UTC)
 * I have no strong feelings about whether the Happy/Sad ball video belongs here. But the decision to remove was made by a single editor who has far less experience as a WP editor than I.  I will return the video and let this article's community decide whether it should be re-deleted. Guy vandegrift (talk) 23:39, 30 May 2024 (UTC)
 * It's a bloody awful explanation of what is going on and since I have no interest in happy and sad ball sales I'd be inclined to delete it. I could of course rewrite their pathetic explanation for use in their marketing material, but I won't. Greglocock (talk) 01:02, 31 May 2024 (UTC)
 * As far as I am concerned, a "vote" of 2-1 is enough to declare a consensus to delete. Give me a couple of days to write something on Wikiversity that will be sister-linked out of this article.--Guy vandegrift (talk) 20:29, 4 June 2024 (UTC)

Newton meter sec
First paragraph says Impulse is Newton meter sec is NM/sec. What? — Preceding unsigned comment added by Longinus876 (talk • contribs) 22:28, 10 March 2016 (UTC)


 * Not so. It says N.s or kg.m/s both are dimensionally equal. Dger (talk) 23:03, 10 March 2016 (UTC)

Make technical articles understandable
This article on Impulse is a technical article so it should be consistent with the guidelines at WP:Make technical articles understandable. Unfortunately, the article lead, in particular, does not fare well when assessed alongside the guidelines. I propose to write an improved lead.

My major objection in the lead is the first sentence which says In classical mechanics, Impulse is the integral of a force, F, over the time interval, t for which it acts. This sentence falsely implies that an understanding of the concept of impulse is only available to readers who already have an understanding of vector calculus! The only pre-requisite for understanding impulse is that the reader has a rudimentary understanding of momentum. Impulse in its basic form is simply the difference between the initial momentum of an object, and its momentum at some later time. (In the case of rectilinear motion, both momentum and impulse can be treated as scalar quantities. It is that simple.)

Wikipedia guidelines show that this first sentence in the lead is unnecessarily complicated. For example:
 * 1) At MOS:FIRST it says The first sentence ... should be in plain English.
 * 2) At MOS:INTRO it says Make the lead section accessible to as broad an audience as possible. In general, ... but avoid difficult-to-understand ... mathematical equations and formulas.
 * 3) At WP:EXPLAINLEAD it says Terminology in the lead section should be understandable on sight to general readers ...

I intend to amend the article so that impulse is explained in three steps:
 * first step: impulse is the difference between initial momentum, and momentum at a later time. Momentum and impulse are both vector quantities.
 * second step: impulse given by a force F acting for a time interval Δt is the product FΔt. The direction of the impulse is the same as the direction of the force F.
 * third step: impulse given by a varying force F(t) in the time between t1 and t2 is the integral of F with respect to time, between the time interval t1 to t2.

Any comments will be welcome. Dolphin ( t ) 12:32, 9 July 2023 (UTC)


 * Two weeks have passed without objection to my proposal above. I have amended the lead - see my diff. Dolphin ( t ) 12:41, 23 July 2023 (UTC)