The question: (I am given a diagram; I'll attempt to describe it here.) Consider a frictionless, 12000-kg roller coaster that starts at rest at the top of a hill, point A, 95 m high. It goes all the way down the hill and coasts horizontally (for an unspecified distance) before reaching point B (0m high) . Calculate: a) The force that must be applied to bring it to a stop at point B b) The work done to bring it to a stop at point B My answers: a) Now, I usually don't post a question without SOME attempt at an answer, but I'm really stumped here. If I can determine the magnitude of the force of the roller coaster at B, it's simply that magnitude in the opposite direction. However, I can't because F = ma, and I can't find the acceleration because it's an expression of change in velocity over time, and I can't figure out the time because no distance is given! *head explodes* Please, somebody start me off on the right foot here!