# A concept question got deleted

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1. Feb 8, 2015

Greetings,
in this link there's a picture of a slide
I posted it in a thread in which I asked a question, but it got deleted by "Nugatory", because he thought it was a "hw question".

My question was regarding the formula on the right "v0x = v * d/(sqrt(d^2 + (h-y0)^2)", asking where the formula comes from.
Plus, there are no values in this slide, so you'd only find a general solution, not specific one. I say, it's a concept problem.
It seems that the mod who deleted my thread misplaced his judgement.

I won't rest until I hear from other mods that they honestly believe this was a hw question. Come on, look me in the eye and tell me.

2. Feb 8, 2015

### Staff: Mentor

It doesn't matter if it is actual homework as long as it can be handled as homework, (is asking an explanation for a question).. His decision was correct. I see you haven't bothered to read our rules, which explain this.

3. Feb 8, 2015

### Staff: Mentor

From the rules (https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/ under Homework Guidelines):
I concur with Nugatory's decision.

4. Feb 9, 2015

Do you realize I'd easily scoop out threads that are similar or can be easily be subject to deletion according to what you've just said? Just to name a few from the recent ones:
Joule-Thomson-Coefficient (JTC)
OP asks for values to plug in into variables in the formulas posted.

Linear Expansion
OP asks for "the procedure to solve this problem", whereas I, inquired about an existing one (e.g. why is there "(h-y0)" in the formula), because I wanted to understand how it came to be.

Why is the answer to this question "No change"
While the OP asks why the answer is the answer, I merely inquired why a certain formula in the slide is the formula.

Also, here

the OPs ask about formulas one way or another, that's what I did too, I saw a formula, and I wanted to get an explanation as to why it looks the way it looks like. Except, I provided a picture and context for better understanding about the formula. Did I need to simply rephrase what the slide said? I bet if I only posted a text, there wouldn't have been a problem. I also wager, if I you didn't see the slide, you wouldn't be able to say that it come from a "textbook styl
So is that it? I was supposed to sacrifice the visuals in order to make the question appear less like a hw?

"You know, there is a formula to calculate horizontal and vertical velocities of a dart that had been fired from a gun at a monkey at height h,
here it is:
"v0x = v * d/(d^2 + (h-y0)^2)

And I just don't get, where does h-y0 come from? Or what was used to construct this formula? Can someone back it up a few steps?"

But such a thread wouldn't have been as clear as with the attached screenshot of a slide.

btw,
This one is a bit different, though, since OP has already found the answer, but is confused about it.
So does it mean, that if I find a legit answer using correct formulas I might inquire about it in the general physics sub-forum?
Something similar happened in my case as well, only I wanted to know more about the formula that helps to get the final answer.

The discussion problem didn't come from a textbook. So I'd suggest to specifically list the sources, data from which cannot be inquired about in any sense.
Note again these ones: 1, 2
Formulas in here could only come from "textbook style exercises".

So again, if I only mentioned horizontal velocity, omitting the slide, you wouldn't be able to say it comes from an exercise/problem. Besides, even if you go to Physics topics like this one. There is almost always an example/problem after the explanation of a concept.

Does it mean you shouldn't reference such examples if you have question about a concept?

Last edited: Feb 9, 2015
5. Feb 9, 2015