1. The problem statement, all variables and given/known data A skier is pulled up by a towrope up a frictionless ski slope that makes an angle of 12 degrees with the horizontal. The rope moves parallel to the slope with a constant speed of 1.0 m/s. The force of the rope does 900 J of work on the skier as the skier moves a distance of 8m up the incline. If the rope moved with a constant speed of 2 m/s, how much work would the force of the rope do on the skier as the skier moved a distance of 8m up the incline? 2. Relevant equations W=KE or W=KE+PE 3. The attempt at a solution This is a rather conceptual problem in my opinion. So I know the work-kinetic energy theorem. change in K=W. However, my question is: Does it only apply to a system where there is only kinetic energy present or it can be applied to a system where both Kinetic energy and potential energy present. I didn't use K=W, I had W=KE+PE. KE is 0, so W=PE. Because in this case, clearly, there are both Kinetic energy and Potential energy (8m) on the skier. But my teacher still used change in K=W=0, and since the work includes the work from the rope and gravity, they must be same in magnitude and opposite in direction. I hope someone can clarify things for me. thanks.