# A question (which now looks like it was previously incomplete) being modified in such away that the previous answers become useless

This question was posted by user 202. As can be seen from the edit history that the question was incomplete at first(though I didn't knew that till today) (the previous question was scattered all over the post (and till now it almost is).

The initial question was:

Using Bernoulli's equation, it can be shown that the water velocity depends on the height of a tank relative to the end of a hose. In reality I find a smaller hose produces a greater velocity on exit than a larger hose. What have I overlooked to cause this disagreement?

$$v=\sqrt{\frac{2(\rho g h-Losses)}{\rho}}$$

The OP gave a bounty of 150 reps and I therefore invested some time to answer the question as it was in original form (but I also gathered the spread out information from his/her comments,etc.) and then I discovered today that OP found that his/her original question was lacking information (which was much crucial in answering it).

But as can be seen from its current form the previously given answers have now became irrelevant (though I have modified my answer).

So what should we do now?

The dilemma is due to the fact that without this newly added information the question becomes trivial but the answers become relevant and with this information the answers become irrelevant but the scope of the question increases.

Also the OP provides most of the information in his/her answer.

• – ACuriousMind Mod
Commented Jan 4, 2020 at 11:31
• This might be a good lesson in not sinking a lot of time into a question that should have been closed from the beginning. If you thought "the question was incomplete", then this should have indicated to you to not answer. Commented Jan 4, 2020 at 14:22
• @Aaron No I initially didn't thought that the question was incomplete I just thought it was scattered a bit but now it's completely different situation.
– user249968
Commented Jan 4, 2020 at 14:24
• I'm directly quoting your post though. Commented Jan 4, 2020 at 14:32
• @Aaron I recently learned that topic so I thought to give it a try and typing what I learned over here made quite good impression on my mind.
– user249968
Commented Jan 4, 2020 at 14:43
• I'm glad you are learning more about physics :) I am just talking about questions/answers here on this site. If you think a question is unclear, incomplete, off topic, etc. then giving an answer to the question indicates that you think questions like that belong on this site. Commented Jan 4, 2020 at 14:48
• @Aaron then question was quite a bit old so I thought it was genuine.
– user249968
Commented Jan 4, 2020 at 15:14
• The question is less than 2 weeks old, and I don't think the genuineness of the post was ever in question. Commented Jan 4, 2020 at 15:49
• @Aaron Sorry I wasn't trying to mean that (my English is sometimes a bit poor). Also I have became a member of the site just 14days ago so I can't distinguish like a pro which question is bad and which one is good for the site (though I always try to read old meta post to get such informations).
– user249968
Commented Jan 4, 2020 at 16:01

As pointed out here and here questions should not be edited to make the current answers invalid. In this case the extra detail doesn't seem to make things too bad, but for yourself you didn't edit the question; you posted an answer. So what are some options for when, in general, you think your answer no longer applies to a changed question?

1. Do nothing

2. Don't change your answer, but at the beginning of the answer put in something that says your answer was for version "v#", for whatever version number # you were answering

3. Don't change your answer, and flag the question for a moderator to review. If they think the new edit is too disruptive to the current answers, they may choose to rollback the question to a previous version.

4. Edit your answer to fit the new question.

5. Combine 2 and 4 by making your edit fit both the old and new versions.

What you choose to do is up to you, and in general will depend on your/other's answers as well as the extent of the edit to the question.