1. The problem statement, all variables and given/known data Hi all. We have that the work W equals Ui - Uf (respectively the initial and final potential energy). Let us say that a stone has a height 10 m, and falls down. We say that positive x is upwards. Now W = [itex]\int F \cdot dl = F(x_f-x_i)=U_f-U_i[/itex], since F and dl both point downwards. But this result does not correspond to what I wrote above. What am I doing wrong here? Thanks in advance. Sincerely, Niles.