8.6:
Non-conservative Forces
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.
8.6:
Non-conservative Forces
Non-conservative forces are dissipative forces such as friction or air resistance. These forces take energy away from a system as it progresses. Unlike conservative forces, non-conservative forces do not have potential energy associated with them. This is because the energy is lost to the system and cannot be turned into useful work later.
Also unlike their conservative counterparts, they are path-dependent; where the object starts and stops does matter. For example, a grinding wheel applies a non-conservative force because the work done depends on how many rotations the wheel makes. In addition, a non-conservative force turns a macroscopic movement into a microscopic movement. For example, when a ball hits a bat, it creates a sound, which is a microscopic motion. Also, the shape of the ball is momentarily deformed due to the collision with the bat; when the ball bounces from the bat, it returns to its original shape. Throughout all of this, the atoms of the ball, bat, and the atmosphere will experience vibration and lose some of their energy in the form of heat.
This text is adapted from Openstax, University Physics Volume 1, Section 8.2: Conservative and Non-Conservative Forces.