Re: Dragonfire11 pinch-hitting for the Dawg
Measure the diameter of the disk. Divide by 2 and square the result. Multiply by PI (~3.14159). And that's all she wrote!
Makes no difference if it is spinning or not other than the difficulty in measuring it. It is actually more interesting if the disc has a hole in the middle like a CD.
So... A standard CD diameter is 12 cm on the outside, and just under 1.5 cm on the inside. The area of a spinning CD is therefore approximately:
(12/2) * (12/2) * PI = 113.1 sq cm
MINUS the hole
(1.5/2) * (1.5/2) * PI = 1.8 sq cm
Equals
111.3 sq cm
Which is the answer to the CD question.
And no, I am not making this up!
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