Potential energy due to a constant force of gravity

The potential energy due to a constant force of gravity is

$E_{\mathrm{PG}} = m g h,$

where $h$ is the height above the reference level. If we are below the reference level, the potential energy is negative.

The potential energy due to gravity in position (1):

$E_{\mathrm{P}1} = W_{1 \rightarrow 0} = m g h_1.$

The potential energy due to gravity at the reference level:

$E_{\mathrm{P}0} = W_{0 \rightarrow 0} = 0.$

The potential energy due to gravity in position (2):

$E_{\mathrm{P}2} = W_{2 \rightarrow 0} = m g h_2 \cos 180° = - m g h_2.$