So I was watching some of those physics videos posted in schoolwork board, and although he probably didn't make an error here, I don't think I understand it. Here's the pictues. I'll elaborate after it so you guys know what I'm talking about: http://img144.imageshack.us/img144/6632/88907417sb7.png [Broken] When he broke the downward mg force into its components (mg cos theta = ma sub x and mg sin theta = ma sub y), shouldn't it be mg sin theta instead, and likewise for the other? I thought that when you break a vector into its parts, sine is associated with the y axis and cosine for the x. Maybe I'm having a brain fart, but I swear I had those vector components figured out. Thanks ahead of time.