This is seems like an easy question.... 1. The problem statement, all variables and given/known data A single conservative force acts on a 5.00 kg particle. The equation Fx = (2x + 4) N describes this force, where x is in meters. As the particle moves along the x axis from x = 2.20 m to x = 6.60 m. Calculate the change in the potential energy of the system 2. Relevant equations 3. The attempt at a solution Since it just only involves horizontally, I thought the Potential Energy would be zero, but it's telling me it's wrong. ?