I'm quite puzzled as to why this answer I wrote got three downvotes (here).

The OP's question indicates they had a fundamental misunderstanding and probably got lost while self-studying the subject. Something which I can relate to as I self-study as well. So, due to that, I thought of writing the answer from scratch and explaining each concept with the best idea's I could get.

In comparison to mine, some of the almost dismissive answers were accepted over mine and it was this which led me to question the real purpose of the site. Does this site want answers with references and citations or just superficial answers with none of those?

From what I've heard people say, I understood this site as a knowledge repository/place where people could pool in knowledge to help a large group of people. Yet narrow and short answers are preferred over long ones that take time and effort to write.

Maybe my points and my answer is factually wrong... I don't know. I based my knowledge of my textbooks and made sure to say where exactly I got my ideas from so that my answer would be open for criticism.

The purpose of this post is to ask what exactly am I doing wrong... I perhaps guessed that it may have been that my answer was more tending to the teaching side than a direct answer side, but I felt op was so misguided that I had to go out and write it all.

Further, let's take the OP's question out of the picture. Even then, I do think that my answer would be useful for a large audience. I mean, wasn't this the reason that homework questions are shunned upon? (That they only help a narrow group of people.)

I recall once reading an established user of this website saying that the votes are a measure of how useful your questions and answers are for the site. I do not have the exact quote/citation. So, correct me if I am wrong, does this mean that people think my question is reducing the qualify of the site somehow?

One of the main reasons, I preferred this site over other q&a sites is that people were supposed to give trustworthy feedback and answers but I really am not feeling it on this one.

The actual question of the OP:

I felt some people are upvoting answers which is not even related to the OP's question. One person answered momentum conservation using the third law which was not even related to the OP's question...

I really can't understand why there is no decrease in momentum when kinetic energy is decreased in an inelastic collision.

This is the real question contained in the OP's subject and it is an exact quote which I took. They are simply asking how it is so in an inelastic collision that momentum is conserved, but kinetic energy is changed.


When I said useful to a wider audience, I meant this:

I wrote that as a point here because the OP had pinned up a few specific points out of the topic. I took those topics to the fundamentals and explained from the ground up. I was pretty certain that the OP was misguided as soon as I saw that they were asking about Noether's theorem for explaining the kinetic energy loss inelastic collision.

I did not mean that I think answers which are completely derailed from questions should be seen as valuable.

On the individual freedom's to vote:

True, I agree, but I imagine this site to be something more scientific rather than an opinion site. Sure, sometimes things are so complicated that we may have to bring in opinions here and there, but I think we should have the courtesy to explain what is wrong in a piece before giving it a negative reception.

When I got three downvotes I felt that maybe I am doing something very incorrect because it was the first time I got that many downvotes on an answer. I can not see it myself, but if someone else can see it then I'd be happy to listen if they were to point out legitimate criticism on the material that I have written.

  • 2
    $\begingroup$ 1. Your "here" goes to a random comment, not to your answer. Did you mean to link to physics.stackexchange.com/a/583302/50583 instead? 2. While answers should be useful more generally than just to the specific OP, answers that are correct but don't really answer the question (or do so in a convoluted way) are also not what we're looking for here, so "taking the question out of the picture" is not useful in understanding how other users assess answers. $\endgroup$
    – ACuriousMind Mod
    Oct 2, 2020 at 17:38
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    $\begingroup$ 3. Individual users are free to vote as they please - if these specific users haven't seen fit to leave a comment on your question, it's unlikely they'll feel compelled to answer here either, and ultimately only they know why they voted the way they did. $\endgroup$
    – ACuriousMind Mod
    Oct 2, 2020 at 17:38
  • $\begingroup$ Why do you think that I took the question out of the picture..? I literally addressed every single point that op wrote out explicitly. As per individual users being free to vote, due to the exceptional number of downvotes , I assume that maybe something is actually severly wrong with my answer. And honestly I can not see the mistake within the limits of my knowledge and hence I asked here $\endgroup$
    – Babu
    Oct 2, 2020 at 17:43
  • $\begingroup$ Your last paragraph starts with "Further, let's take op's question out of the picture", which is what I was referring to. $\endgroup$
    – ACuriousMind Mod
    Oct 2, 2020 at 17:44
  • $\begingroup$ I wrote that as a point here because op had pinned up a few specific points out of the topic.. I took those topics to the fundamentals and explained from the ground up. I was pretty certain that op was misguided as soon as I saw that they were asking about noether's theorem for explaining the kinetic energy loss inelastic collision $\endgroup$
    – Babu
    Oct 2, 2020 at 17:46
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    $\begingroup$ I'm not one of the downvoters, but when I looked at your answer I thought it was too much like a chapter in a book, and that a more concise answer would have been better. Your verbose writing style might be working against you. $\endgroup$
    – D. Halsey
    Oct 2, 2020 at 22:16
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    $\begingroup$ The title here is a little misleading since you really are just asking what's wrong about your specific answer rather than asking about votes in general. At least, I think this is what is going on, this question seems a little unfocused. $\endgroup$ Oct 3, 2020 at 4:04
  • $\begingroup$ The question I asked is something I can refer to explain my concerns concretely ... if this post was without a question then I don't think it would make sense $\endgroup$
    – Babu
    Oct 3, 2020 at 5:41
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    $\begingroup$ @BioPhysicist I also find the title misleading. A more specific title “why did this answer of mine get downvotes” or something like this that points to queries on a specific post would have been better. $\endgroup$ Oct 3, 2020 at 13:47

3 Answers 3


I find your answer to be overly long; the essential remains buried somewhere within the technical.

The quote is the second part is long and unnecessary and in fact confusing as it goes into tangents on vibrations and such stuff. The second part (containing the quote) is in fact neatly summarized by the last paragraph of this part, which makes the rest moot.

In your example (part 3) you poorly highlight the various momenta in the problem: it’s not clear at all why a final state with $0$ velocity is possible, which is IMO part of the confusion in the original question.

The point of your derivation in part 4 is to show that some energy is lost, but this point IMO would have been better conveyed by a 1d example rather than a full-vector collision.

Now: I did not downvote your answer. You obviously put some effort in it, and it’s not technically wrong (that I can see); I just happen to think it’s at the wrong level and it’s unclear (I reserve my downvotes on answers to more aggravating cases than this). However, I can easily see how some might get irritated by the meandering and the overly complicated nature of your solution.

FYI I rarely comment on my downvotes as experience has shown it rarely resolves anything but tends to produce discussions that are not very constructive.

Nota: I even find this meta question is overly long and difficult to follow.


I did not downvote your answer (I did not even see it until I saw this meta post), but to my mind the biggest problem with it is right at the beginning, where you derive the equation $K=p^2/(2m)$ and conclude that KE is a function of momentum and mass. This is of course true for a particle but not for a system of more than one particle, which is what the OP is clearly asking about. It seems to me that this is very likely to confuse the OP, and that this is a problem even if the rest of the answer eventually clears up the confusion.

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    $\begingroup$ I agree - this was my reaction to that answer as well. $\endgroup$ Oct 4, 2020 at 13:18

When I got three downvotes I felt that maybe I am doing something very incorrect ...

Not necessarily. Your answer got two upvotes as well, so some people liked it. If I were you I would focus on the bigger picture, which is that your answers are mostly getting upvotes and your reputation is steadily increasing. Speaking personally, if one of my answers gets a downvote with an explanation in the comments then I will think about how I might improve it, but I just ignore a downvote without explanation.


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