1. The problem statement, all variables and given/known data I am having difficulty with a problem: A race care goes around a level, circular track with a diameter of 1.00 km at a constant speed of 90.0 km/h. Wha tis the car<s centripetal acceleration in m/s^2? 2. Relevant equations Ac=v^2/r 3. The attempt at a solution I'm not quite sure if I'm supposed to find the radius of the 1.00 diameter or if I simply use the 1.00 km as my radius in the above equation...?