Non-conservative forces are those forces that cause a change in the total energy of the system by converting it into heat, light, or any other form of energy. Friction, air resistance, and viscosity are a few examples of non-conservative forces. They are also known as dissipative forces as they cause the mechanical energy to be lost or dissipated in the system. For example, when a car skids on a road, it loses mechanical energy as a part of its kinetic energy gets converted into thermal energy due to friction. To understand the work done by non-conservative forces, consider two identical objects sliding down two different slides simultaneously. The object moving on slide A would lose more energy due to friction. Therefore, the work done by the frictional force on slide A is greater than that on B. Hence, the work done by non-conservative forces is irreversible, cannot be described as a function of potential energy, and depends only on the path taken by the object.