Hot CD's and DVD's, is it okay?

[Brian R.]

I used metrics...

By the way, what is the data diameter of a 3.5" HD disk?

[This message has been edited by Brian R. (edited 04 September 2000).]

[agallag]

Sorry, I didn't bother to measure a CD, and assuming 5 1/4" screwed up my calculations. There's still something very wrong with Pace's calculations though, at least in his miles to kilometres conversions.

I'll check the diameter of a 3.5" HD platter on tuesday, since I have a disassembled 230MB drive hanging in my cubicle at work

[agallag]

The varying results between brian and rags probably results from the fact that 4 21/32" = 11.826875 cm, not 11.84 cm. It also depends on how precisely you punch Pi into your calculator. Using 3.14 would give a different result for circumference then using 3.141592653589 (etc.). I'm sure both of your methods are correct

[Brian R.]

My weakpoint was I used an old cheap plastic ruler. Could have been 11.83 cm, depending on your eyesight.

[Rags]

By data diameter, do you mean the surface area? I can do square miles/ hour if ya like

Rags

This brings up a good thinking question. Which is a greater amount, seconds in a century, or square inches in a square mile?

[Brian R.]

I'm not thinking that well this late. I'm still trying to find the best UT server. Ever since I got ADSL, I'm searching servers. What a blast some of them are.

Since I have ADSL, the question comes up as to what has the bigger effect on playability, download speed or upload speed or equal? Trying to determine if increasing my download speed will be worth the extra money. Going to the next ADSL level triples my download speed, but has the same upload speed.

Also, what is the significance of the red square icon that pops up in the middle right side of the UT screen occasionally? Some form of ping warning?

[This message has been edited by Brian R. (edited 04 September 2000).]

[agallag]

Let's see, for seconds in a century, you've got 60*60*24*365.25*100 = 3,155,760,000 (days per year is not exact, but close enough)

Square inches in a square mile... hmmm... given that there are 63,360 inches in a mile, you just have to square that for square inches in a square mile, giving 4,014,489,600. So, there ya go.

-=-=-
Andrew

[agallag]

Just found out that there's 365.242198781 days in a year, so that makes 3,155,692,597.46784 seconds in a century

[This message has been edited by agallag (edited 04 September 2000).]

[Brian R.]

Agallag - Actually, your calculation indicates there are 3,155,692,597.47 seconds in a year. Your precision was unjustifiably inflated.

Just say a report that the founder of Amazon.com has a standard interview question he has asked of potential managers. "Using a back of the envelope calculation, estimate the number of gasoling filling stations in the United States".

Anyone who doesn't know care to guess?

[This message has been edited by Brian R. (edited 04 September 2000).]

[Pace]

Ok - I think my 'math' was right - just the method! And the mph/kph coversion was also wrong.

I think I worked out distance based on the diameter - when it should be circumference. I did fail Uni maths though and I'm waiting on the result of my second sitting...

So then - I assumed that a CD was 5" - it's actually 4 3/4" or 12cm (based on genuine numbers and I've checked to see that the 12cm refers to the outermost point on the CD (non-data). So here goes with a calculation to see what's the maximum speed reached by the outermost point on a CD!

Diameter: 12cm = 0.12m

Circumference: Diameter * Pi = 2 * 3.14 * 0.06 = 0.38m

Revs/min: 9,000

Revs/hour: 540,000

1 revolution is 0.38m so 540,000 revs = 540,000 * 0.38 = 205,200m

A CD spinning for an hour would travel 205,200m. Are we all agreed so far? If not we'll fix it later .

205,200m = 205.2km

Therefore our CD spins 205kph.

62 miles = 100 kilometres (I used these figures in reverse - as you guessed)

So 205kph in miles is: 205 * 62 / 100 = 127mph

Anyone who disagrees can only post if they think they can beat a University maths student (well I am for the moment )

I even worked it out pretty exact too - here is to twenty-something places of accuracy 126.21662645062353314847516056664 (as far as WinCalc allows!)

Paul.

Edit: Removing the Pi symbol and 3/4 (didn't think they would turn out!)


[This message has been edited by Pace (edited 04 September 2000).]

[agallag]

Yeah yeah Brian, I know. Windows calculator assumes that you're giving it exactly precise numbers, and gives results to it's full 15 digits of accuracy. I just cut & paste the answer, 'cause I'm a lazy bastard.

-=-=-
Andrew

[Liquid Snake]

Does it really matter how many mph the CD is going?

Brian, the up/down speeds don't affect ping. That's why some people with 144K IDSL can get great pings. ADSL has slightly higher pings because of interleaving. Interleaving increases data reliability, but it also increases ping.

[Rags]

I am no longer a Student, but I graduated, that must count for something. Hmmmm....I wonder if I took math courses back then

Rags

[Pace]

From what I wrote in my Maths exam a few weeks ago I wonder if I took Maths this year!

Brian got the right answer anyway (well close enough - slightly closer than I was that's for sure!)

Paul.

[agallag]

I have some vague memories about somebody trying to teach me some kind of math in a big room with lots of chairs. It may have been an halucination though...

-=-=-
Andrew