Millions…of scientists,
Put down the cold fusion experiments because something really important has come up:
If a person spins a bottle cap on it’s edge as hard as possible, how many revolutions does it make? For this (not so) hypothetical, let’s assume the bottle cap spins for 20 to 25 seconds. Any way to figure this out with this information? If not, what’s a reasonable guess? Let’s say it was a quarter…how many revolutions would that make?
And yes, this is to settle a silly argument.
Depends on how hard you flick it. Around 20 RPS seems a reasonable average. You’d really have to measure it directly to get any kind of accurate figure, though. It’s just too highly variable.
I was worried about that.
Can we assume that the gentleman spinning the cap was giving it all he had? In other words, err on the side of fast. But I assumed that whole “measurement” thing might rear it’s ugly head.
I very roughly measured how fast I can flick my finger. I did this by flicking in front of my TV screen, and counted the number of “finger images” I could see between start and finish, which averaged about 3. That means my finger took about 3 screen refreshes at 60/second to travel the distance, which I measured as 3.75 inches. 3.75/(3/60) = 75 inches per second. If we assume the edge of the bottle cap travels at the same rate, and its diameter is one inch, I get about 23.8 RPS for my hardest flick.
That’s incredibly helpful, Q.E.D.. Thanks.
Initially, but slows down at what rate?
Not a clue. Someone else can figure that part out.
That someone? Not me. I was learning the banjo when I should have been studying science.
It can be done simply by experiment. Get a strobe light whose knob shows its blink rate (can be ordered various places) and a stopwatch. Or sync up the light with some known rotational speed of something like a bicycle wheel to normalize a flashing frequency.
Set the strobe, then flick the coin. At a certain point, the coin will appear to be standing still, while it is making one revolution every 1 flash. Mark the time down.
Wait.
The coin will then get out of sync, but will again as it slows reach a point where it appears to be standing still, when it now makes one revolution every 2 flashes. Mark the time down.
The rest is arithmetic.
That’s just plain ingenious!
But isn’t interlacing a factor?
Thank you. 
Shouldn’t be. The NTSC interlacing scheme draws 30 interlaced frames per second like this. The flicker rate is therefore 30 x 2 or 60 Hz. It’s actually 59.94 Hz, but who’s counting?
