The elastic potential energy is the energy stored in a stretched spring. The energy may be used to do work, for instance, or may be converted into kinetic energy of an object attached to the spring. It may also be converted into gravitational potential energy. A nonconservative force is one which dissipates mechanical energy by converting it to another form such as heat. The work done by a nonconservative force depends on the path taken.
Friction is a nonconservative force.
The greater the length of the path taken as an object moves from one point to another, the more work is done by the frictional force. Conservative Forces and Potential Energy Let's look more closely at the conservative force and the potential energy function. The work done by a conservative force on a particle is This is written more conveniently as So if a conservative force does positive work on an object, the potential energy of the object becomes lower. Conservation of Mechanical Energy For a closed system, the total amount of energy within the system is constant, or conserved. The energy may change form many times, as with the Wilberforce pendulum, but the total will remain the same.