12-2 Potential energy y 1, Definition 62 When work is done in a system(such as ball and arth) by a conservative force, the configuration of its rts changes, and so the potential energy changes from its initial u. value to its final value u We define the change in potential energy associated with the conservative force as A=-U1=-=「F(124) Ch 12 Energy II: Potential energyCh.12 Energy II: Potential energy 12-2 Potential energy 1.Definition When work is done in a system (such as ball and earth) by a conservative force, the configuration of its parts changes, and so the potential energy changes from its initial value to its final value . We define the change in potential energy associated with the conservative force as: Ui U f  ΔU =U −U = −W = − F ds f i   (12-4)