Okay. So i've got three cars that are traveling along a hilly road. One is at the beginning, where its flat, one is at the bottom of the hill, one is at the top. Each is traveling at 21 m/s. I am supposed to find tangential acceleration for each. I tried: a = v^2 / r but that is radial acceleration. I know the formula for tangential acceleration is a = (alpha)(r) but i am given no times or anything to calculate alpha. I'm thinking I need a relation of some sort between radial and tangential accelerations. Anyone have any guidelines?