The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time? There's several graphs, some sinusoidal, some completely flat, some like absolute value, etc. There are also qa semicircle shaped one, which is what I picked. #10 on this (pdf) has an image of each graph. It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?