1. The problem statement, all variables and given/known data So, I'm studying for the MCAT and I can't for the life of me understand why I'm wrong here. Here is the question: A skier is given a strong push so that he slides up the hill in Figure 2 (it’s a non-descript right triangle with a stick man skier on it, the angle of incline is irrelevant) for a certain distance with a μk =.1. When he gets to the highest point, he slides back down. How does the acceleration of the skier on his ascent compare to the acceleration on his descent? Do not consider the acceleration of the push. A. The acceleration on the descent is smaller in magnitude than on the ascent. B. The acceleration on the ascent is smaller in magnitude than on the descent. C. Both accelerations are the same. D. The accelerations have the same magnitude but different directions. 2. Relevant equations Fk=FNμk FN= mgcosΘ. Fk= mgsinΘ. 3. Attempts at explanation So, these questions tend to be broadly theoretical, and the answer to this particular one is B. The book reasons that friction is additive as the skier is moving up the hill and subtractive as the skier moves down, i.e. the forces on the skier moving up the hill (gravity + friction) add, and the forces as she moves down the hill (gravity - friction) subtract. My issue here is that friction opposes movement/force, not slope. There would still be some friction as the skier went up the hill, right? Right? Or am I losing my mind?