Junior Member
Real Speeds..
What is the formula to work out what MPH the powerball is effectively doing when you have a RPM score ?
If anyone knows, this would be very interesting.
A friend says 15000rpm=1200mph but i dont think hes right.
Im sure its something to do with Outside Diameter versus RPM mulitplied by Pi.
Senior Member
Just find the circumference of the ball in MILES and multiply it by the RPM * 60.
The circumference of the ball is approx 10cm (from eye). This is 0.1m which is 1x10^-4 km which is 6.2x10^-5 miles.
Say your RPM is 12000, then 60x12000 = 720000
72000 x 6.2x10^-5=
44.6mph (If all my calculations are correct!)
Stephen
Edit: Circumference is closer to 17cm = 76.1mph
To calculate mph for different scores:
0.006337986 * YOUR RPM
Last edited by stephenk; 06-03-2006 at 17:41.
Member
That's ridiculous. It would mean that it has broken the sound barrier, and I'm not sure how holding something that's spinning at that rate it going to affect your arm.Originally Posted by Quasar
From my estimation:
5cm X 3.14 = 15.7cm, approx. 16cm. 16cm X 15000rpm = 240,000CM covered when Powerball has spun 15k rotations. 240,000CM * 60 minutes = 14,400,000 cm/h, thus 144000 m/h, and then 144KM/H. Still pretty damn fast, it's faster than a Volvo, that's for sure
Junior Member
I think I have figure out the formula for fast translations on you speed for the US and Metric. I measured the diameter as close as i could without taking it apart... I got about 2.25in or 5.71cm
So here is what you have to do to get MPH and KMPH
MPH= Rpm times 7.07, then divide by 63360, multiply by 60<-- final answer in MPH
KMPH= Rpm multiply by 17.94, divide by 100,000, multiply by 60<-- answer in KMPH
And there you have it, RPM in MPH and KMPH
Hope it helps!
Senior Member
wouldn`t that be easier just saying for getting MPH just multiply the RPM by 0,0067 and for KPH multiply by 0,01076 ? I just used your numbers.
Junior Member
Many Thanks for your help guys, this has helped
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