# Work and Energy - Mission WE9 Detailed Help

 When an object's total mechanical energy is NOT conserved, ____. List all that apply ... .
 Work - Mechanical Energy Relationships: If non-conservative forces do net work upon an object, then the total mechanical energy of that object is changed. The sum of the kinetic and potential energies will change as work is done upon the object.
 Definition of Conservative Force: All the different types of forces that could do work upon an object can be categorized as either conservative or non-conservative forces. A conservative force is a type of force that serves to transform an object's energy between kinetic and potential. When only conservative forces do work upon an object, the energy of the object changes forms (KE to PE or vice versa) without changing the total amount of mechanical energy. Mechanical energy is said to be conserved.   Definition of Non-conservative Force: All the different types of forces that could do work upon an object can be categorized as either conservative or non-conservative forces. A non-conservative force is a type of force that changes the total amount of mechanical energy possessed by an object. When non-conservative forces do work upon an object, the total amount of mechanical energy changes. Mechanical energy is not conserved.
 Mechanical energy takes two forms - kinetic energy and potential energy. When non-conservative forces do work upon an object, the total amount (or sum) of these two forms changes. An example would be a car skidding to a stop along a level roadway. Because of the work done by friction on the car, there is an overall loss of mechanical energy. The overall energy - mechanical and non-mechanical does not change. The mechanical energy (kinetic energy, in the case of the skidding car) is transformed into non-mechanical form such as heat and sound energy.