Potential energy ($V$ or $U$) is defined specifically in the context of conservative forces, such as gravity or spring forces . The relationship between a conservative force ($F$) and potential energy is given by $F = -dV/dx$, which implies that the work done by a conservative force is equal to the negative change in potential energy ($\Delta V = -W_c$) . Therefore, when a conservative force does positive work on a body, the potential energy decreases . Conversely, if work is done against a conservative force (meaning the system or an external agent overcomes the force), that work is stored as an increase in the potential energy of the system . Non-conservative forces, like friction, do not have an associated potential energy .