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**1. Homework Statement**

Hi all.

We have that the work W equals U

_{i}- U

_{f}(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.