Students were discussing a problem in which the class was asked to find the acceleration of a cart rolling up and down an incline at the instant the cart was at the very top of its path. Malia says, At the top the velocity has to be zero so the acceleration has to be zero too. Sasha disagrees saying, No, the velocity is changing at the top so the acceleration cant be zero. Who do you agree with? Discuss the reason for your answer and explain why the one who is wrong might legitimately be confused about which answer is correct.