Work and Energy - Mission WE5 Detailed Help

Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as conservative (or internal) forces?


 
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 net 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.


 
There are two forces commonly discussed in MOP questions that serve as conservative forces - gravity and spring. The force of gravity, when it does work, serves to change gravitational potential energy into kinetic energy or vice versa. The spring force, when it does work, serves to change elastic potential energy into kinetic energy or vice versa. All other forces are regarded as non-conservative forces that serve to change the total amount of mechanical energy in one of its two forms.