1. The problem statement, all variables and given/known data A roller coaster is on a track that forms a circular loop in the vertical plane. If the car is to just maintain contact at the top of the loop, what is the minimum value for its centripetal acceleration at this point? A) 2g downward B) g downward C) 2g upward D) g upward E) 0.5 downward 2. Relevant equations fcp = m(v^2 / r) 3. The attempt at a solution I thought since normal force and weight are pointing in the same direction, the Fcp would be mg + mg = 2mg. But the correct answer is g downward. Please explain.