1. The problem statement, all variables and given/known data Part A A cheetah, the fastest of all land animals over a short distance, can accelerate from zero to 18.0 m/s in three strides and to a full speed of 31.3 m/s in seconds. Assuming the first three strides are each 4.2 m long and that acceleration is constant until the cheetah reaches full speed, what is the cheetah's acceleration (in m/s2)? Part B If in part (a) of this question the cheetah's first three strides were each 4.6 m long, how many seconds would it take to reach its full speed? 2. Relevant equations 3. The attempt at a solution Ok so for Part A I use the above equation: 31.3^2 - 18^2 = 2*a*12.6 (12.6 = 3 strides) 979.69 - 324 = 25.2a 655.69 = 25.2a a = 26.02 Ok this is where it gets weird. That is not the answer, but when I divide it by 2, I get 13.01 which is within 0.1 of the answer showing on the online test. Every time I try this question with different velocities, I am within 0.1 of the online test's correct answer. The test gives me the mark, but I can not help but wonder if it's me doing something wrong or is the programming on the online test a bit off. I am not really concerned about Part A, but Part B I just can't understand. I have tried using the rearranged velocity equations and the simple speed equation, but I still can't get the answer shown. The answer for Part B is 2.67 seconds. EDIT: Sorry about the attachment, not sure how to make it appear within the post.