From the previous section we know that the work done by a conservative force in terms of the change in potential energy is given by

`Delta U=-W_C`............(1)

Where `U` is the potential energy and `W_c` is the work done by a conservative force. From the work-energy theorem , we know that

`W_(n et)=Delta K`

Where `W_(n et)` represents the sum of work done by all the forces acting on the mass.

If a particle is subjected to only conservative forces , then

`W_C=W_(n et)=Delta K`...............(2)

Thus, the equation (1) becomes,

`Delta U=-Delta K` or `Delta U+Delta K=0`................(3)

`text(Important Concept: -)`
The equation (3) tells us
that the total change in potential energy plus the
total change in kinetic energy is zero if only
conservative forces will acting on the system.
`(K+U) = 0 ...(4)`
or E = 0
where E=K+U
The quantity E = K + U is called the total
mechanical energy.