Conservative and Non-Conservative Forces

Idea: It is not always true that the work done by an external force is stored as some form of potential energy. This is only true if the force is conservative:

W_c = F_c^ext(x_B - x_A) = PE_A - PE_B. (5)

Definition: The work a conservative force does on an object in moving it from A to B is path independent - it depends only on the end points of the motion. Examples: the force of gravity and the spring force are conservative forces. For a non-conservative (or dissipative) force, the work done in going from A to B depends on the path taken. Examples: friction and air resistance.