Question

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 7.55 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 6.43 rev/s. What is the centripetal acceleration of the ball at 7.55 rev/s? What is the centripetal acceleration at 6.43 rev/s?