Rpm related to velocity and diameter

[cgaday]

How do you determine RPM when given your velocity and the radius or diameter of the cirlcle?

thanks in advance.

 

[Stonebridge]

One circumference is 2Pi.r. That's distance traveled in one revolution.
If you travel at speed v, then the time T it takes to travel that distance = distance divided by speed.
Finally, if it takes T seconds for one revolution, you do 1/T revolutions per second.
Put it all together to get the answer.

 

[cgaday]

so for r = 1.5 ft therefore 2pi(1.5) = 9.42 feet
speed equals 95.34 ft/s

T = distance/speed = 9.42 ft/ 95.34 ft per sec = .0988

1/T = 1/.0988 = 10.121 rev/s

IS this correct.

 

[Stonebridge]

Yes, that looks fine to me. :)