Gravitational Potential Energy, and Conservation of Energy

There are many different forms of energy. It is possible to convert energy from one form to another.
Gravitational potential energy (GPE) is associated with an object's mass and its position. It is equal to the work one must do to lift an object some distance against a gravitational force.
```
                    GPE  =  (mass) * g * (height)
```
If an object falls, it gives up its gravitational potential energy. The gravitational force does work on it, and speeds it up. Its GPE is converted into kinetic energy.

Mechanical Energy is defined as the sum of the kinetic and gravitational potential energy:

                    E    =    KE      +    GPE

                         = 0.5 m*v^2  +   m*g*H

In the absence of friction, or any external force, the mechanical energy in a system is conserved.

                 E(initial)            =         E(final)

           KE(initial) + GPE(initial)  =  KE(final) + GPE(final)

A conservative force is one which does the same amount of work on an object that moves from point A to point B, no matter what path it takes along the way.
Gravity is a conservative force.

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