I know this depends on a lot of factors but I heard a revolution can happen in 0.02 second is this the case? I can't even stop my stop watch that fast?
This is a math-only question, and no one has explained the formulas. Also I like the idea of this simple question having multiple answers so...
RPM is Revolutions Per Minute, but we want a time in seconds. When you hear that word "per" it means division. So, what we have is 4000 revolutions / 1 minute (where / is the division symbol). This easily converts to 4000 revolutions / 60 seconds. The result of that (4000/60=) is 66.66 revolutions / 1 second.
Now we have revolutions per second, but you want seconds per revolution (what we have, flipped upside down). So, simply enough, we flip the whole thing upside down to get 1 second / 66.66 revolutions, and the result is (1/66.66=) 0.015 seconds / 1 revolution.
Finally, flip that around grammatically and we get "1 revolution takes 0.015 seconds". Which is 15 milliseconds, but I'll leave that conversion as an exercise for the reader.
60 seconds. RPM stands for Revolutions Per Minute. if you have one RPM then it takes 60 seconds to do a complete revolution.
Now there are ways to convert from RPM (Revolutions Per Minute) to seconds per revolution or other such measurements as mentioned in other answers however they do not answer the actual question asked of how fast one RPM is.