gravity

Work by gravity

Gravity F=mg does work W=mgh along any descending path

Gravity exerts a constant downward force on every object. Near the surface of the earth the acceleration due to gravity is g=9.8 m.s⁻² and the gravitational force on an object of mass m is F_g=mg. It is convenient to imagine this gravitational force concentrated at the center of mass of the object.
If an object is displaced upwards or downwards a vertical distance y₂ - y₁, the work W done on the object by its weight mg is:

where F_g is weight (pounds in imperial units, and newtons in SI units), and Δy is the change in height y. Notice that the work done by gravity depends only on the vertical movement of the object. The presence of friction does not affect the work done on the object by its weight.