The problems reads, A carnival Ferris wheel has a 14.2m radius and completes one revolution about its horizontal axis in 10.1s. Consider the time interval from the instant when a passenger is at the lowest point of the uniform circular motion to a clock reading 5.05 seconds later. What was the magnitude of the passenger's average acceleration during this time interval? Do I use the formula (they're suppose to be vectors) a=(-rwcoswt)i+(-rwsinwt)j? I really don't have any direction towards solving this problem. Any hints would be wonderful.