The question is: If an astronaut who can physically withstand acceleration up to 9 times that of free fall (9g) is being rotated in an arm of length 5.0m what is the maximum number of revolutions per second permissible. I approached this by considering 9g to be the centripetal acceleration (because as there is no other acceleration in circular motion). I've worked out the time for one revolution many times, but I don't know how to do this the other way around. What equations should I use? I know I haven't fallowed the strict guide to homework questions but I don't know the equations I could use other than that for centripetal acceleration, a = v^2/r, but that doesn't tell me anything about the maximum number of revolutions per second. Can someone push me in the right direction for the start? I just look at the question and all equations related to circular motion and just nothing comes to my head.