This week, we will continue our discussion of energy.
We will introduce the concept of potential energy--
which is related to the work done by a conservative force,
and also the concept of total mechanical energy--
which is defined as the sum of the kinetic and potential
energies.
We will demonstrate that the total mechanical energy
of a system remains constant if only conservative forces are
acting.
This is known as the Principle of Conservation
of Mechanical Energy.
We will also see how the work done
by any non-conservative forces causes
the total mechanical energy of the system
to change, usually causing mechanical energy to be
lost from the system.
Finally, we will see how graphs of a system's potential energy,
as a function of position, provide
an elegant way of understanding the behavior
of the system for a given value of the total mechanical energy.