Lie Ryan

I need to integrate ∫ (1/2 * v²) * dt, I got:

∫ (1/2 * v²) * dt = ∫(1/2 * (dx/dt)²) * dt = 1/2 * ∫(dx²/dt)

but that doesn't seem to make sense to me, how do I integrate that?

Ok, so here's the scenario. I'm writing a program to simulate a system, and I need to find an analytical solution to this (I don't want to use numerical approximation or a physics library since I'm doing this for learning as well). I am a programmer not physicist, so please tell me if there is a flaw in my understanding or hidden assumptions in my physics that I hadn't covered.

Assuming an object of constant mass and constant drag coefficient (= 0.409 on a ball), and constant reference area (= diameter on a ball); and assuming an environment with constant fluid density.

There will be multiple Forces acting on an object, currently I'm thinking about

- gravity (F = m * a; m = mass, a = gravity but can be any constant force);

- drag (F = 1/2 * ρ * v² * C * A; where ρ = fluid density, C = drag coefficient, A = reference area);

- collision (F = ?, haven't figured this out yet, how do you model the dynamics of collisions?)

The equation for Force assuming constant mass is:

F = m * (dv/dt)

therefore assuming constant mass:

v = 1/m * ∫ F * dt

therefore since F = drag + gravitation = (1/2 * ρ * v² * C * A) + (m * a):

v = 1/m * ∫ ((1/2 * ρ * v² * C * A) + (m * a)) * dt

v = 1/m * (∫ (1/2 * ρ * v² * C * A) * dt + ∫(m * a) * dt)

v = 1/m * (ρ * C * A * ∫ (1/2 * v²) * dt + (m * (a*t + v0))) ; assuming constant mass, ρ, C, and A

That's how I got stuck with ∫ (1/2 * v²) * dt, or is there a better ways to do the calculation?

In C, char is basically a very small int, so the output of:

char d = 'd';

char c = 'c';

cout << d - c << endl;

the output is "1"

I understand that this is because in ASCII, the characters happens to have this relationship.

What I want to know is how standardized is this. In some obscure systems, where the standard charset is not ASCII, will 'd' - 'c' NOT result in 1? Does the C/C++ standard specify the default input/output encoding?

AFAIK, in some older encodings, the layout of the charmap is very different. Some interlaces between uppercase and lowercase (AaBbCc...XxYyZz instead of ASCII's ABC...XYZ...abc...xyz), so if a system has this encoding as its default encoding, the program's output may become "2".

What about other languages?

Wikipedia's entry on "plastic" says "Synthetic rubbers are not plastics", however looking at the circumstances (Synthetic rubber has its own section in the plastic article; the claim is just a one-liner that contradicts the rest of the section; fact that synthetic rubber is hydrocarbon-based polymer; etc), it appears that that statement is fishy. We know Wikipedia can be a bit unreliable at times.

So... is rubber a type of plastic?

Additionally, what makes a rubber, a rubber?

or if that sounds too philosophical, what properties (chemical, physical, or otherwise) that allows us to classify a material as rubber. Likewise for other types of plastics too, if you know.

An article I found: http://www.plasticsindustry.com/synthetic-rubber.a... seems to say that rubber is plastic (and very confident about it); however, I want to double check before correcting the wikipedia article.

How should I account Money Order?

I'm using GnuCash to track of my personal finance. Recently, I bought a money order to pay someone else, how do I account this.

Currently I'm doing this:

Credit Cash on Wallet for the Money Order + MO's Fee

Debit Miscellanous for MO's Fee

Debit Checking account for Money Order

Credit Checking account for Money Order

Debit Expense for Money Order

but using Checking Account seems... wrong, but I don't send money order that often. Should I open a new account? What you'd reckon I should name it?

Grammatically, I think it should be "it began" (don't count on me on this, I'm not a native speaker of English, and my instinct is often smarter than my conscious brain in English language), but somehow I feel it's better to use "it begins".

What's your say about this? The event that "begins" or "began" is still happening until the moment of speaking << perhaps this is the reason why my instinct feels it should be "it begins"

Do you think "everytime" or "every time" is correct? Or is it both?

I'm asking for personal answer/preference/thought/etc

since all the dictionaries I checked (dictionary.com, m-w.com (Merriam-Webster, onelook.com, encarta.msn.com, dictionary.cambridge.org) do not list "everytime" or only list a song with the name "Everytime" (as encyclopedic entry).

I have a 1GB Kingston USB flashdisk, and Vista says my flashdisk could be used for ReadyBoost, however I noticed that after I put my computer to sleep Vista couldn't read data from my flashdisk anymore (when I entered the USB root folder from "Computer", it shows an empty folder, Explorer doesn't hang though. Fortunately, my files would show up again after I unplug and replugged the USB disk.)

One of the reason I plugged my flashdisk on sleep is so ReadyBoost could accelerate the wake up proceess, however if Vista couldn't even read from my disk it wouldn't speed up the wake up.

Do you know why this is happening? Is it a bug on Vista or the USB flashdisk driver or what? Is there something I could do to make Vista able to read the flashdisk after sleep?

FYI:

My laptop is HP Compaq Presario V3221AU

I need to design a board that will reverse the direction of the current when there a switch is pressed, and the second switch signal would reverse it again. Please tell me the name of such a layout (if it exist), or explains how it works.

So basically, how long is the execution time or time needed to execute an operator?

+ (Addition)

- (Subtraction)

* (Multiplication)

/ (Real Division)

\ (Integer Division)

Mod (Modulus)

= (Assignment)

Also, if you know: Math (Math.Sin, Math.Pow, etc)

Also, some other common operators I might've missed.

My current condition:

CPU: AMD 64 bit

OS: XP SP2 32 bit

I'm Installing Ubuntu on top of VMWare. Which one is better to install? 32 bit version, following the Host OS or the 64 bit version following the CPU? Why?

If an object that have mass is pulled by gravity, it'd accelerate with time. Would someday the object travels faster than light?

Let's just imagine that the object would never reach the center of the gravitation.

As we know, when we travels near lightspeed, mass increases, but gravity's acceleration to an object is not affected by mass isn't it?

level 5:

Participating since June 13, 2006

Points: 5,272

Level: 5

Points this week: 2,775 <<< and the last question she answered was 3 weeks ago.

Questions (18)Answers (266)

Best Answer: 31 (11%)

I have to answer over 1000 questions, with best answer rate of 21% (>200 questions) to get as much point as her.

Do you think this is a bit fishy? I take this statistic from a real user (http://answers.yahoo.com/my/profile;_ylt=Aii.tFGdj... )

Please, tell me if I'm wrong, but I'm quite sure noone would get his 2500 points only by voting and rating questions (which are not recorded on our userpage).

(if you're wondering why I found her, it's because she is right below me in this week's leaderboard, and I also suspect that she is not alone)

level 5:

Participating since June 13, 2006

Points: 5,272

Level: 5

Points this week: 2,775 <<< and the last question she answered was 3 weeks ago.

Questions (18)Answers (266)

Best Answer: 31 (11%)

I have answered over 1000 questions, with best answer rate of 21% (>200 questions).

Do you think this is a bit fishy? I take this statistic from a real user (http://answers.yahoo.com/my/profile;_ylt=Aii.tFGdj... )

Please, tell me if I'm wrong, but I'm quite sure noone would get his 2500 points only by voting and rating questions (which are not recorded on our userpage).

from Bono to Stephen King. And they all have the same traits:

- All of them asks controversial questions

- All of them have a Yahoo's Staff note, confirming that the question is asked by the real [enter celebrity's name].

- All of them are featured questions

- All of the account used to ask the celebrity question is never used to ask or answer any other question.

- All of the account uses the proper name of the celebrity.

And perhaps, these traits too:

- They all have a gigantic amount of answers, typically > 10 000, which is very rare, even for a featured questions.

- They all asks an open ended questions that invites us to gives opinions, and seems to be more like a social campaign.

- Some other traits you might notice, but I do not.

What could be the problem is? After a complete reinstall, I installed some drivers, etc. Up till here the mouse works fine. Then I reboot the machine, the mouse won't move. After a bit of testings here and there I found that the problem lies on USB, the USB can't be detected by Windows, and thus my mouse too. Seeing that I've just reinstalled my Windows, I think that I'd just reinstall it again, but the prblem persists even after the second reinstall.

I need to make an array of a class.

A Class need to use New Keyword to declare, but an array cannot be used together with New Keyword, this contradicts.

http://answers.yahoo.com/question/index;_ylt=Ak9Bv...

http://answers.yahoo.com/question/index;_ylt=Atv5o...

http://answers.yahoo.com/question/index;_ylt=AtHiV...

http://answers.yahoo.com/question/index;_ylt=AjkCM...

http://answers.yahoo.com/question/index;_ylt=AuAb7...

http://answers.yahoo.com/question/index;_ylt=Auq_q...

http://answers.yahoo.com/question/index;_ylt=AtHiV...

http://answers.yahoo.com/question/index;_ylt=AlUup...

http://answers.yahoo.com/question/index;_ylt=AqGST...

How do we convert an angle from Gradient to Radian Degree AND from Radian and Degree to Gradient.

How do we convert angles to and from gradient?

Note: There will be no points for Radian to Degree OR Degree to Radian.

*** SPOILER ALERT ***

You should be someone that don't care spoilers or someone who has finished reading this Japanese Manga.

If you want to continue, scroll below

Does anyone know why Resshin which is Ouka's (Recca's father) soul can be in Recca's body while obviously when Recca was born, Ouka is still alive. I've read the manga to the end, but can't find out how it could be like that. The seven dragons are all transfered from Ouka to Recca when he was born, but Ouka's soul surely can't be transferred while Ouka is still alive can't he?

Anyone know a script for taking the arguments from the URL?

So if the URL is http://www.a.com/?g=10

I want to take the 10 from g=10