A non-conservative force is a type of force in physics that does not conserve mechanical energy. When a non-conservative force acts on an object, the work done by the force depends on the path taken by the object. In other words, the work done by a non-conservative force is path-dependent.
Examples of non-conservative forces include friction, air resistance, and tension in a rope that is being stretched or compressed. These forces can do work on an object, but the work done depends on the path taken by the object.
Non-conservative forces are important in mechanics because they can cause a decrease in the total mechanical energy of a system. This means that the kinetic energy and potential energy of a system can be converted into other forms of energy, such as heat or sound, by the action of non-conservative forces.
In contrast, conservative forces, such as gravity and electrostatic forces, do conserve mechanical energy, and the work they do on an object depends only on the initial and final positions of the object.