1. The problem statement, all variables and given/known data I know the answer and how to get it, but it doesn't make sense because ac points down and so does g. So why do they seem to cancel each other out? What is the minimum constant speed a motorbiker needs in order to make it around a vertical loop with a radius of 3 meters? 2. Relevant equations I know that I have to make ac = g. So, ac = 9.8m/s^2. v = √(r*ac) 3. The attempt at a solution v = √(r*ac) = √(3*9.8) = 5.4m/s This all seems to imply that ac and g cancel out, but how can they when they are both in the same direction?