\text { Work-Potential-Energy Theorem: } W_{\text {ext }}=\Delta P E_{\text {ays }} \text { and } W_{\text {int }}=-\Delta P E_{\text {ays }} \text {. } Problem 8. True or False: The work done on a system by an internal conservative force, such as the force of gravity or the elastic spring force, can be expressed as the negative of the change in the potential energy of the system: Wcons= ΔΡΕ.

Fig: 1

Fig: 2