This is mostly a conceptual confusion I'm having, not a specific problem, so it didn't seem like it'd fit under hw problems. I'm having trouble understanding when potential energy should or shouldn't be used in a energy conservation equation. When looking at a problem with a skier going down a hall, we were given his weight, initial velocity, slope of the hill, value of friction force, and distance traveled, and were asked to find his final velocity. We found the net work done, added it to the initial kinetic energy, and found his final velocity through his final kinetic energy. We didn't use the potential energy of gravity at all, but later we have an equation that says initial and final potential energy of gravity should be on the respective sides of the equations. Why is it they weren't used for a problem of a skier skiing down a hill? Does the net work account for it? Thanks!