Question

Why does the work-energy theory ignores potential energy?

Answer 1

Potential Energy cannot be defined for all forces. Where potential energy can be defined, change in PE is equal to the negative of the work done.
`W_{"net"} = \Delta K = -\Delta U`

Explanation:

Work-Energy Theorem does not ignore potential energy. Just that potential energy cannot be defined for all forces.

Potential energy can only be defined for conservative forces, whereas kinetic energy is always well defined. Work-Energy theorem expressed in terms of kinetic energy is always applicable, irrespective of what kind of force is doing the work.

In situations where potential energy can be defined, change in potential energy is exactly equal to the negative of change in kinetic energy, in which case the Work-Energy theorem becomes

`W_{"net"} = \Delta K = - \Delta U`

Where potential cannot be defined it is simply

`W_{"net"} = \Delta K`