[SOLVED] Work and Energy Hello, I'm a little new to this forum but I would really appreciate some help with this particular problem. A roller coaster reaches the top of the steepest hill with a speed of 5.8 km/h. It then descends the hill, which is at an average angle of 25 degrees and is 50m long. What will the speed be when it reaches the bottom. assume the coefficient of friction (uk) = 0.12 So the first thing I did was convert the 5.8 km/h to 1.61 m/s to get consistent units. I know that KE initial + PE initial = KE final + PE final. I also know I have to break things up into components. I know Fx=mgcos25. But I think I'm screwing up the Fy component. After that I'm lost and I'm not sure where to go from there. Any suggestions and help will be greatly appreciated.