When work is done to stretch a rubber band, the object gains potential energy --- elastic potential energy.

When the rubber band contracts, it can do work on something else, decreasing its own potential energy.

Find the elastic potential energy stored in a drawn bow if it takes an average force of 100N to pull the arrow back a distance of 0.5 meters.

The elastic P.E. is just the work done on the bow --- (100N)(0.5m) = 50Nm = 50J.

Examples --- What this is an example of