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Well ... I can see the windmills now ... I've actually lived here for ten years and have seen each type that are used here up close. The big ones have blades about ten foot long ... given the equation for circumference C = pi · D that means that the C = 31.4 feet. Though the big ones take over 2 seconds to go around (I can time it from where I sit) for arguments sake I'll say it takes one second per revolution or 60 RPM. 31.4 feet per second or 1884 feet per minute (31.4 FEET X 60) or 113040 feet per hour (31.4 feet x 3600). There are 5280 feet in a mile so that makes or 21.4 mph ... thats a long way from 200mph. Even if my math is flawed ... I can see the blade tips from here ... there is NO WAY that they are moving 200 mph. At 200 MPH the prop would have to spin at a little less than 600 RPM

OPPS D= 20 feet so C=62.8 feet ... Though the big ones take over 2 seconds to go around (I can time it from where I sit) for arguments sake I'll say it takes one second per revolution or 120 RPM. 62.8 feet per second or 3768 feet per minute (62.8 FEET X 60) or 226080 feet per hour (62.8 feet x 3600). There are 5280 feet in a mile so that makes or 42.8 mph ... thats a long way from 200mph. Even if my math is flawed ... I can see the blade tips from here ... there is NO WAY that they are moving 200 mph. At 200 MPH the prop would have to spin at a little less than 300 RPM

Well ... I can see the windmills now ... I've actually lived here for ten years and have seen each type that are used here up close. The big ones have blades about ten foot long ... given the equation for circumference C = pi · D that means that the C = 31.4 feet. Though the big ones take over 2 seconds to go around (I can time it from where I sit) for arguments sake I'll say it takes one second per revolution or 60 RPM. 31.4 feet per second or 1884 feet per minute (31.4 FEET X 60) or 113040 feet per hour (31.4 feet x 3600). There are 5280 feet in a mile so that makes or 21.4 mph ... thats a long way from 200mph. Even if my math is flawed ... I can see the blade tips from here ... there is NO WAY that they are moving 200 mph. At 200 MPH the prop would have to spin at a little less than 600 RPM

Well, I think you have a math error there. A large windmill today has a diameter of about 2-300 feet not 10 feet. A very popular size is the Vestas V47 and it is not large but medium size. It is 155 feet in diameter. You are right on the rotational speed so lets say 155*pi feet per second for a tip speed. That's about 500 feet per second or 300ish mph.

I envy your nearness to them. I drive 80 miles to Waverly Ia to see a Neg Micon NM52 which is 52 meters in diameter and rated at 900kw.