studying different types of energy. In general, energy is defined as the capacity to do work. Just about any process can be viewed as some kind of energy transfer process, and none of them involve any net gain or loss of energy. This is defined by the conservation of energy principal. Use the 2 links below

http://hyperphysics.phy-astr.gsu.edu/hbase/egex2.html

http://www.sparknotes.com/physics/workenergypower/conservationofenergy/section1.rhtml

How would you define this principal? What is an example?