1. The problem statement, all variables and given/known data An athlete swings a ball, connected to the end of a chain, in a horizontal circle. The athlete is able to rotate the ball at the rate of 8.16 rev/s when the length of the chain is 0.600 m. When he increases the length to 0.900 m, he is able to rotate the ball only 6.32 rev/s. (a) Which rate of rotation gives the greater speed for the ball? [Which I got is 6.32] (b) What is the centripetal acceleration of the ball at 8.16 rev/s? [?] (c) What is the centripetal acceleration at 6.32 rev/s? [?] 2. Relevant equations a[c] = v^2/r T = 2∏r/v 3. The attempt at a solution I know the I need to find the velocity to solve this question, but that is where I am having trouble. I am assuming 8.16 and 6.32 are the periods. So I get: v = 2∏(0.300)/(8.16) for B; and then use this to find acceleration which is: a[c] = (0.23)^2/(0.300) = 1.176. But this is not the correct answer! Why?